Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Flavonoid
open-in-new
<h2 id="history">History</h2> <p>In the 1930s, <a href="/facts/Albert_Szent-Gy%C3%B6rgyi/DTBenFpC">Albert Szent-Györgyi</a> and other scientists discovered that <a href="/facts/Vitamin_C/IA2f1fTm">Vitamin C</a> alone was not as effective at preventing <a href="/facts/Scurvy/VEpTjUWM">scurvy</a> as the crude yellow extract from oranges, lemons or paprika. They attributed the increased activity of this extract to the other substances in this mixture, which they referred to as "citrin" (referring to citrus) or "Vitamin P" (a reference to its effect on reducing the permeability of <a href="/facts/Capillary/4BIzKJAe">capillaries</a>). The substances in question (<a href="/facts/Hesperidin/nPPl1JEp">hesperidin</a>, <a href="/facts/Eriodictyol/YA7dXnTX">eriodictyol</a>, hesperidin methyl chalcone and <a href="/facts/Neohesperidin/vXxaLlfx">neohesperidin</a>) were however later shown not to fulfil the criteria of a vitamin,<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> so that this term is now obsolete.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> <h2 id="biosynthesis">Biosynthesis</h2> <p class="note">Main article: <a href="/facts/Flavonoid_biosynthesis/qune0rRo">Flavonoid biosynthesis</a></p> <p>Flavonoids are secondary metabolites synthesized mainly by plants. The general structure of flavonoids is a fifteen-carbon skeleton, containing two benzene rings connected by a three-carbon linking chain.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> Therefore, they are depicted as C6-C3-C6 compounds. Depending on the chemical structure, degree of oxidation, and unsaturation of the linking chain (C3), flavonoids can be classified into different groups, such as anthocyanidins, flavonols, flavanones, flavan-3-ols, flavanonols, flavones, and isoflavones.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> Chalcones, also called <a href="/facts/Chalconoids/UGo4KFQU">chalconoids</a>, although lacking the heterocyclic ring, are also classified as flavonoids. Furthermore, flavonoids can be found in plants in glycoside-bound and free aglycone forms. The glycoside-bound form is the most common flavone and flavonol form consumed in the diet.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <h2 id="functions-of-flavonoids-in-plants">Functions of flavonoids in plants</h2> <p>Flavonoids are widely distributed in plants, fulfilling many functions.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> They are the most important <a href="/facts/Biological_pigment/7Lv9jMEd">plant pigments</a> for flower coloration, producing yellow or red/blue pigmentation in petals designed to attract <a href="/facts/Pollinator/DBJNeDtv">pollinator</a> animals. In higher plants, they are involved in UV filtration, symbiotic nitrogen fixation, and floral pigmentation. They may also act as chemical messengers, physiological regulators, and cell cycle inhibitors. Flavonoids secreted by the root of their host plant help <i><a href="/facts/Rhizobia/xGRcYg5h">Rhizobia</a></i> in the infection stage of their <a href="/facts/Symbiosis/MrBArRGa">symbiotic</a> relationship with legumes like peas, beans, clover, and soy. Rhizobia living in soil are able to sense the flavonoids and this triggers the secretion of <a href="/facts/Nod_factor/mzFGmmVz">Nod factors</a>, which in turn are recognized by the host plant and can lead to root hair deformation and several cellular responses such as ion fluxes and the formation of a <a href="/facts/Root_nodule/qUFHMpsq">root nodule</a>. In addition, some flavonoids have inhibitory activity against organisms that cause plant diseases, e.g. <i>Fusarium oxysporum</i>.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> </p> <h2 id="subgroups">Subgroups</h2> <p>Over 5000 naturally occurring flavonoids have been characterized from various plants. They have been classified according to their chemical structure, and are usually subdivided into the following subgroups (for further reading see<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a>): </p> <h3>Anthocyanidins</h3> <p><a href="/facts/Anthocyanidin/ha2b1NQM">Anthocyanidins</a> are the <a href="/facts/Aglycone/kAgQHUem">aglycones</a> of <a href="/facts/Anthocyanin/eUY12Frv">anthocyanins</a>; they use the <a href="/facts/Flavylium/QTplu8Ez">flavylium</a> (2-phenylchromenylium) ion skeleton.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> </p> Examples: <a href="/facts/Cyanidin/AhwFgtq1">cyanidin</a>, <a href="/facts/Delphinidin/BS8sklyj">delphinidin</a>, <a href="/facts/Malvidin/az2VBexe">malvidin</a>, <a href="/facts/Pelargonidin/Fq22s9QQ">pelargonidin</a>, <a href="/facts/Peonidin/DPGtYGrd">peonidin</a>, <a href="/facts/Petunidin/U6t2xlpN">petunidin</a> <h3>Anthoxanthins</h3> <p><a href="/facts/Anthoxanthin/6mGSeVdR">Anthoxanthins</a> are divided into two groups:<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> </p> <table><tbody><tr><th rowspan="3">Group</th><th colspan="4">Skeleton</th><th rowspan="3">Examples</th></tr><tr><th rowspan="2">Description</th><th colspan="2">Functional groups</th><th rowspan="2">Structural formula</th></tr><tr><th>3-hydroxyl</th><th>2,3-dihydro</th></tr><tr><td><a href="/facts/Flavones/5Anj1LGD">Flavone</a></td><td>2-phenylchromen-4-one</td><td>✗</td><td>✗</td><td></td><td><a href="/facts/Luteolin/a9Hfax2L">Luteolin</a>, <a href="/facts/Apigenin/HCWcxzDv">Apigenin</a>, <a href="/facts/Tangeritin/rGTKvF5b">Tangeritin</a></td></tr><tr><td><a href="/facts/Flavonols/cFmUlN8u">Flavonol</a>or<a href="/facts/Flavonols/cFmUlN8u">3-hydroxyflavone</a></td><td>3-hydroxy-2-phenylchromen-4-one</td><td>✓</td><td>✗</td><td></td><td><a href="/facts/Quercetin/Ed1BP1YD">Quercetin</a>, <a href="/facts/Kaempferol/mLleEu8u">Kaempferol</a>, <a href="/facts/Myricetin/HrE6o1Ns">Myricetin</a>, <a href="/facts/Fisetin/2P31nfTU">Fisetin</a>, <a href="/facts/Galangin/85zll251">Galangin</a>, <a href="/facts/Isorhamnetin/0rFp0wzx">Isorhamnetin</a>, <a href="/facts/Pachypodol/dGPmeQhX">Pachypodol</a>, <a href="/facts/Rhamnazin/I9JKf0JR">Rhamnazin</a>, <a href="/facts/Pyranoflavonol/KrP73ucx">Pyranoflavonols</a>, <a href="/facts/Furanoflavonol/amV3gkQN">Furanoflavonols</a>,</td></tr></tbody></table> <h3>Flavanones</h3> <p><a href="/facts/Flavanone/lMEpwpcx">Flavanones</a> </p> <table><tbody><tr><th rowspan="3">Group</th><th colspan="4">Skeleton</th><th rowspan="3">Examples</th></tr><tr><th rowspan="2">Description</th><th colspan="2">Functional groups</th><th rowspan="2">Structural formula</th></tr><tr><th>3-hydroxyl</th><th>2,3-dihydro</th></tr><tr><td><a href="/facts/Flavanones/lMEpwpcx">Flavanone</a></td><td>2,3-dihydro-2-phenylchromen-4-one</td><td>✗</td><td>✓</td><td></td><td><a href="/facts/Hesperetin/Evv28WfB">Hesperetin</a>, <a href="/facts/Naringenin/7tnKVrbd">Naringenin</a>, <a href="/facts/Eriodictyol/YA7dXnTX">Eriodictyol</a>, <a href="/facts/Homoeriodictyol/JTJsJKso">Homoeriodictyol</a></td></tr></tbody></table> <h3>Flavanonols</h3> <p><a href="/facts/Flavanonol/R2TGKeSP">Flavanonols</a> </p> <table><tbody><tr><th rowspan="3">Group</th><th colspan="4">Skeleton</th><th rowspan="3">Examples</th></tr><tr><th rowspan="2">Description</th><th colspan="2">Functional groups</th><th rowspan="2">Structural formula</th></tr><tr><th>3-hydroxyl</th><th>2,3-dihydro</th></tr><tr><td><a href="/facts/Flavanonols/R2TGKeSP">Flavanonol</a>or3-Hydroxyflavanoneor2,3-dihydroflavonol</td><td>3-hydroxy-2,3-dihydro-2-phenylchromen-4-one</td><td>✓</td><td>✓</td><td></td><td><a href="/facts/Taxifolin/AA6C2vn7">Taxifolin</a> (or <a href="/facts/Dihydroquercetin/AA6C2vn7">Dihydroquercetin</a>), <a href="/facts/Dihydrokaempferol/25zR28rT">Dihydrokaempferol</a></td></tr></tbody></table> <h3>Flavans</h3> <p>Include <a href="/facts/Flavan-3-ol/W2h9843C">flavan-3-ols</a> (flavanols), <a href="/facts/Flavan-4-ol/VFQquhrb">flavan-4-ols</a> and <a href="/facts/Flavan-3,4-diol/8Ct3bfWc">flavan-3,4-diols</a>. </p> <table><tbody><tr><th>Skeleton</th><th>Name</th></tr><tr><td></td><td><a href="/facts/Flavan-3-ol/W2h9843C">Flavan-3-ol</a> (flavanol)</td></tr><tr><td></td><td><a href="/facts/Flavan-4-ol/VFQquhrb">Flavan-4-ol</a></td></tr><tr><td></td><td><a href="/facts/Flavan-3,4-diol/8Ct3bfWc">Flavan-3,4-diol</a> (leucoanthocyanidin)</td></tr></tbody></table> <ul><li><a href="/facts/Flavan-3-ols/W2h9843C">Flavan-3-ols</a> (flavanols) <ul><li><a href="/facts/Flavan-3-ols/W2h9843C">Flavan-<i>3-ols</i></a> use the 2-phenyl-3,4-dihydro-2<i>H</i>-chromen-<i>3-ol</i> skeleton</li></ul> Examples: <a href="/facts/Catechin/EaYR3n8G">Catechin</a> (C), <a href="/facts/Gallocatechin/nRanQrgS">Gallocatechin</a> (GC), Catechin 3-gallate (Cg), Gallocatechin 3-gallate (GCg), <a href="/facts/Epicatechin/EaYR3n8G">Epicatechins</a> (<a href="/facts/Epicatechin/EaYR3n8G">Epicatechin</a> (EC)), <a href="/facts/Epigallocatechin/nRanQrgS">Epigallocatechin</a> (EGC), <a href="/facts/Epicatechin_3-gallate/LMNoKFcr">Epicatechin 3-gallate</a> (ECg), <a href="/facts/Epigallocatechin_3-gallate/xbbwrnsC">Epigallocatechin 3-gallate</a> (EGCg) <ul><li><a href="/facts/Theaflavin/TVufyT4U">Theaflavin</a></li></ul> Examples: <a href="/facts/Theaflavin-3-gallate/pKo4SNbT">Theaflavin-3-gallate</a>, Theaflavin-3'-gallate, <a href="/facts/Theaflavin-3,3%27-digallate/Dg2uYpI7">Theaflavin-3,3'-digallate</a> <ul><li><a href="/facts/Thearubigin/0h62rLVR">Thearubigin</a></li> <li><a href="/facts/Proanthocyanidins/QpD5hGkc">Proanthocyanidins</a> are dimers, trimers, oligomers, or polymers of the flavanols</li></ul></li></ul> <h3>Isoflavonoids</h3> <ul><li><a href="/facts/Isoflavonoid/CVsGmIlc">Isoflavonoids</a> <ul><li><a href="/facts/Isoflavone/Yfz7RTEo">Isoflavones</a> use the 3-phenylchromen-<i>4-one</i> skeleton (with no hydroxyl group substitution on carbon at position 2)</li></ul> Examples: <a href="/facts/Genistein/XJc73rxA">Genistein</a>, <a href="/facts/Daidzein/AD3o0xGU">Daidzein</a>, <a href="/facts/Glycitein/L4JupYrt">Glycitein</a> <ul><li><a href="/facts/Isoflavane/VWYl1C7P">Isoflavanes</a></li> <li><a href="/facts/Isoflavandiol/VWYl1C7P">Isoflavandiols</a></li> <li><a href="/facts/Isoflavene/3mFBdllH">Isoflavenes</a></li> <li><a href="/facts/Coumestan/YgUz9ucv">Coumestans</a></li> <li><a href="/facts/Pterocarpan/1f08RB7x">Pterocarpans</a></li></ul></li></ul> <h2 id="dietary-sources">Dietary sources</h2> <p>Flavonoids (specifically flavanoids such as the <a href="/facts/Catechins/W2h9843C">catechins</a>) are "the most common group of <a href="/facts/Polyphenol/H6Q7QIQH">polyphenolic</a> compounds in the human diet and are found ubiquitously in plants".<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a><a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> Flavonols, the original bioflavonoids such as <a href="/facts/Quercetin/Ed1BP1YD">quercetin</a>, are also found ubiquitously, but in lesser quantities. The widespread distribution of flavonoids, their variety and their relatively low <a href="/facts/Toxicity/qa96rs60">toxicity</a> compared to other active plant <a href="/facts/Chemical_compound/37FXqqtv">compounds</a> (for instance <a href="/facts/Alkaloids/m6hUXohz">alkaloids</a>) mean that many animals, including <a href="/facts/Human_nutrition/GntDW6oo">humans</a>, ingest significant quantities in their diet.<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> </p><p>Foods with a high flavonoid content include <a href="/facts/Parsley/q6xqWokU">parsley</a>, <a href="/facts/Onion/2ajXf00d">onions</a>, <a href="/facts/Blueberries/2xtgLU6Y">blueberries</a> and <a href="/facts/Strawberry/M4oa6zJ9">strawberries</a>, <a href="/facts/Black_tea/oXG1AP2X">black tea</a>, <a href="/facts/Banana/D6r2qPPq">bananas</a>, and <a href="/facts/Citrus/6FqG38Dk">citrus</a> fruits.<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a> One study found high flavonoid content in <a href="/facts/Buckwheat/vhNC6Ddr">buckwheat</a>.<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> </p><p>Citrus flavonoids include <a href="/facts/Hesperidin/nPPl1JEp">hesperidin</a> (a glycoside of the flavanone <a href="/facts/Hesperetin/Evv28WfB">hesperetin</a>), <a href="/facts/Quercitrin/PejMxYEY">quercitrin</a>, <a href="/facts/Rutin/FNbgcJ6B">rutin</a> (two <a href="/facts/Glycoside/z11RwaaB">glycosides</a> of quercetin, and the flavone <a href="/facts/Tangeritin/rGTKvF5b">tangeritin</a>. The flavonoids are less concentrated in the <a href="/facts/Juice_vesicles/cLWPzLdc">pulp</a> than in the <a href="/facts/Peel_(fruit)/p9J9Kp35">peels</a> (for example, 165 versus 1156 mg/100 g in pulp versus peel of <a href="/facts/Citrus_unshiu/jayYM9SP">satsuma mandarin</a>, and 164 vis-à-vis 804 mg/100 g in pulp versus peel of <a href="/facts/Clementine/FHwBbvHn">clementine</a>).<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> </p><p><a href="/facts/Peanut/dMd0XWsu">Peanut</a> (red) skin contains significant polyphenol content, including flavonoids.<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a><a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a> </p> Flavonoid content in food (mg/100 g)<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a><table><tbody><tr><th>Food source</th><th>Flavones</th><th>Flavonols</th><th>Flavanones</th></tr><tr><td>Red onion</td><td>0</td><td>4–100</td><td>0</td></tr><tr><td>Parsley, fresh</td><td>24–634</td><td>8–10</td><td>0</td></tr><tr><td>Thyme, fresh</td><td>56</td><td>0</td><td>0</td></tr><tr><td><a href="/facts/Lemon/dYYzVCVq">Lemon</a> juice, fresh</td><td>0</td><td>0–2</td><td>2–175</td></tr></tbody></table> <h2 id="dietary-intake">Dietary intake</h2> <p><a href="/facts/Food_composition_data/j7euf6tN">Food composition data</a> for flavonoids were provided by the <a href="/facts/USDA/3PK2rx7C">USDA</a> database on flavonoids.<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> In the United States <a href="/facts/NHANES/r3ID2RVs">NHANES</a> survey, mean flavonoid intake was 190 mg per day in adults, with <a href="/facts/Flavan-3-ol/W2h9843C">flavan-3-ols</a> as the main contributor.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> In the <a href="/facts/European_Union/6GYcR8qM">European Union</a>, based on data from <a href="/facts/EFSA/wooppnvX">EFSA</a>, mean flavonoid intake was 140 mg/d, although there were considerable differences among individual countries.<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> The main type of flavonoids consumed in the EU and USA were flavan-3-ols (80% for USA adults), mainly from tea or cocoa in chocolate, while intake of other flavonoids was considerably lower.<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a><a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a><a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a> </p> <h2 id="research">Research</h2> <p>Neither the United States <a href="/facts/Food_and_Drug_Administration/rCEnh9WB">Food and Drug Administration</a> (FDA) nor the <a href="/facts/European_Food_Safety_Authority/wooppnvX">European Food Safety Authority</a> (EFSA) has approved any flavonoids as <a href="/facts/Prescription_drug/a2zNYPMq">prescription drugs</a>.<a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a><a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a><a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a><a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a> The U.S. FDA has warned numerous dietary supplement and food manufacturers, including <a href="/facts/Unilever/9dnFaVFR">Unilever</a>, producer of <a href="/facts/Lipton/421c40kl">Lipton tea</a> in the U.S., about illegal advertising and misleading <a href="/facts/Health_claim/QS48z3ws">health claims</a> regarding flavonoids, such as that they lower cholesterol or relieve pain.<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a><a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a> </p> <h3>Metabolism and excretion</h3> <p>Flavonoids are poorly absorbed in the human body (less than 5%), then are quickly metabolized into smaller fragments with unknown properties, and rapidly excreted.<a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a><a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a><a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a><a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a> Flavonoids have negligible antioxidant activity in the body, and the increase in antioxidant capacity of blood seen after consumption of flavonoid-rich foods is not caused directly by flavonoids, but by production of <a href="/facts/Uric_acid/gPMSfLcT">uric acid</a> resulting from flavonoid <a href="/facts/Depolymerization/r7QTPbGU">depolymerization</a> and <a href="/facts/Excretion/mspsTfnv">excretion</a>.<a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a> Microbial metabolism is a major contributor to the overall metabolism of dietary flavonoids.<a class="footnote-ref" id="fnref:44" href="#fn:44"><sup>44</sup></a><a class="footnote-ref" id="fnref:45" href="#fn:45"><sup>45</sup></a> </p> <h3>Inflammation</h3> <p><a href="/facts/Inflammation/Ura86MIy">Inflammation</a> has been implicated as a possible origin of numerous local and systemic diseases, such as <a href="/facts/Cancer/PVW6n1D0">cancer</a>,<a class="footnote-ref" id="fnref:46" href="#fn:46"><sup>46</sup></a> <a href="/facts/Cardiovascular_disorders/HD420nMv">cardiovascular disorders</a>,<a class="footnote-ref" id="fnref:47" href="#fn:47"><sup>47</sup></a> <a href="/facts/Diabetes_mellitus/2xeHXbsI">diabetes mellitus</a>,<a class="footnote-ref" id="fnref:48" href="#fn:48"><sup>48</sup></a> and <a href="/facts/Coeliac_disease/AKd5PkTc">celiac disease</a>.<a class="footnote-ref" id="fnref:49" href="#fn:49"><sup>49</sup></a> There is no <a href="/facts/Evidence-based_medicine/InK1lB9l">clinical evidence</a> that dietary flavonoids affect any of these diseases.<a class="footnote-ref" id="fnref:50" href="#fn:50"><sup>50</sup></a> </p> <h3>Cancer</h3> <p><a href="/facts/Clinical_trial/q8LMr832">Clinical studies</a> investigating the relationship between flavonoid consumption and cancer prevention or development are conflicting for most types of cancer, probably because most human studies have weak designs, such as a small <a href="/facts/Sample_size_determination/sf8dAFzq">sample size</a>.<a class="footnote-ref" id="fnref:51" href="#fn:51"><sup>51</sup></a><a class="footnote-ref" id="fnref:52" href="#fn:52"><sup>52</sup></a> There is little evidence to indicate that dietary flavonoids affect human cancer risk in general.<a class="footnote-ref" id="fnref:53" href="#fn:53"><sup>53</sup></a> </p> <h3>Cardiovascular diseases</h3> <p>Although no significant association has been found between flavan-3-ol intake and cardiovascular disease mortality, clinical trials have shown improved <a href="/facts/Endothelial_dysfunction/Gbp1NcY6">endothelial function</a> and reduced <a href="/facts/Blood_pressure/VtqqSM2J">blood pressure</a> (with a few studies showing inconsistent results).<a class="footnote-ref" id="fnref:54" href="#fn:54"><sup>54</sup></a> Reviews of <a href="/facts/Prospective_cohort_study/NeAbQH7s">cohort studies</a> in 2013 found that the studies had too many limitations to determine a possible relationship between increased flavonoid intake and decreased risk of cardiovascular disease, although a trend for an inverse relationship existed.<a class="footnote-ref" id="fnref:55" href="#fn:55"><sup>55</sup></a><a class="footnote-ref" id="fnref:56" href="#fn:56"><sup>56</sup></a> </p><p>In 2013, the EFSA decided to permit health claims that 200 mg/day of cocoa flavanols "help[s] maintain the elasticity of blood vessels."<a class="footnote-ref" id="fnref:57" href="#fn:57"><sup>57</sup></a><a class="footnote-ref" id="fnref:58" href="#fn:58"><sup>58</sup></a> The FDA followed suit in 2023, stating that there is "supportive, but not conclusive" evidence that 200 mg per day of cocoa flavanols can reduce the risk of cardiovascular disease. This is greater than the levels found in typical chocolate bars, which can also contribute to weight gain, potentially harming cardiovascular health.<a class="footnote-ref" id="fnref:59" href="#fn:59"><sup>59</sup></a><a class="footnote-ref" id="fnref:60" href="#fn:60"><sup>60</sup></a> </p> <h2 id="synthesis-detection-quantification-and-semi-synthetic-alterations">Synthesis, detection, quantification, and semi-synthetic alterations</h2> <h3>Color spectrum</h3> <p>Flavonoid synthesis in plants is induced by light color spectrums at both high and low energy radiations. Low energy radiations are accepted by <a href="/facts/Phytochrome/58xIP2wo">phytochrome</a>, while high energy radiations are accepted by <a href="/facts/Carotenoid/Jm2eHYwW">carotenoids</a>, <a href="/facts/Flavin_group/AKg5pskX">flavins</a>, <a href="/facts/Cryptochrome/YS0gfB1X">cryptochromes</a> in addition to phytochromes. The <a href="/facts/Photomorphogenesis/aCfYrYQD">photomorphogenic</a> process of phytochrome-mediated flavonoid biosynthesis has been observed in <a href="/facts/Amaranth/DbgL7rTz"><i>Amaranthus</i></a>, <a href="/facts/Barley/GH7X2qtG">barley</a>, <a href="/facts/Maize/lJ6c5xMH">maize</a>, <i><a href="/facts/Sorghum/D1KNhtdT">Sorghum</a></i> and <a href="/facts/Turnip/dIkKUdIG">turnip</a>. Red light promotes flavonoid synthesis.<a class="footnote-ref" id="fnref:61" href="#fn:61"><sup>61</sup></a> </p> <h3>Availability through microorganisms</h3> <p>Research has shown production of flavonoid molecules from genetically engineered microorganisms.<a class="footnote-ref" id="fnref:62" href="#fn:62"><sup>62</sup></a><a class="footnote-ref" id="fnref:63" href="#fn:63"><sup>63</sup></a> </p> <h3>Tests for detection</h3> <h4>Shinoda test</h4> <p>Four pieces of magnesium filings are added to the ethanolic extract followed by few drops of concentrated <a href="/facts/Hydrochloric_acid/HqItJlUT">hydrochloric acid</a>. A pink or red colour indicates the presence of flavonoid.<a class="footnote-ref" id="fnref:64" href="#fn:64"><sup>64</sup></a> Colours varying from orange to red indicated <a href="/facts/Flavone/5Anj1LGD">flavones</a>, red to crimson indicated flavonoids, crimson to magenta indicated <a href="/facts/Flavonone/J7FEAtLE">flavonones</a>. </p> <h4>Sodium hydroxide test</h4> <p>About 5 mg of the compound is dissolved in water, warmed, and filtered. 10% aqueous <a href="/facts/Sodium_hydroxide/xjtdYtq7">sodium hydroxide</a> is added to 2 ml of this solution. This produces a yellow coloration. A change in color from yellow to colorless on addition of dilute hydrochloric acid is an indication for the presence of flavonoids.<a class="footnote-ref" id="fnref:65" href="#fn:65"><sup>65</sup></a> </p> <h4>p-Dimethylaminocinnamaldehyde test</h4> <p>A colorimetric assay based upon the reaction of A-rings with the chromogen <a href="/facts/P-dimethylaminocinnamaldehyde/8IkzvknH">p-dimethylaminocinnamaldehyde</a> (DMACA) has been developed for flavanoids in beer that can be compared with the <a href="/facts/Vanillin/mBmdAn7I">vanillin</a> procedure.<a class="footnote-ref" id="fnref:66" href="#fn:66"><sup>66</sup></a> </p> <h3>Quantification</h3> <p>Lamaison and Carnet have designed a test for the determination of the total flavonoid content of a sample (AlCI3 method). After proper mixing of the sample and the reagent, the mixture is incubated for ten minutes at ambient temperature and the absorbance of the solution is read at 440 nm. Flavonoid content is expressed in mg/g of <a href="/facts/Quercetin/Ed1BP1YD">quercetin</a>.<a class="footnote-ref" id="fnref:67" href="#fn:67"><sup>67</sup></a><a class="footnote-ref" id="fnref:68" href="#fn:68"><sup>68</sup></a> </p> <h3>Semi-synthetic alterations</h3> <p>Immobilized <i><a href="/facts/Candida_antarctica/uEjd0wko">Candida antarctica</a></i> lipase can be used to catalyze the <a href="/facts/Regioselectivity/m3Bs2Xzl">regioselective</a> <a href="/facts/Acylation/9R8o69jN">acylation</a> of flavonoids.<a class="footnote-ref" id="fnref:69" href="#fn:69"><sup>69</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Phytochemical/Txrr3QVx">Phytochemical</a></li> <li><a href="/facts/List_of_antioxidants_in_food/h2mIAPIY">List of antioxidants in food</a></li> <li><a href="/facts/List_of_phytochemicals_in_food/mkUEqWmm">List of phytochemicals in food</a></li> <li><a href="/facts/Phytochemistry/jnbbfsWz">Phytochemistry</a></li> <li><a href="/facts/Secondary_metabolites/mKnQjBQp">Secondary metabolites</a></li> <li><a href="/facts/Homoisoflavonoid/wa6t4HLK">Homoisoflavonoids</a>, related chemicals with a 16 carbons skeleton</li></ul> <h2 id="further-reading">Further reading</h2> <ul><li>Andersen ØM, Markham KR (2006). <i>Flavonoids: Chemistry, Biochemistry and Applications</i>. Boca Raton, FL: CRC Press, Taylor & Francis. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-8493-2021-7.</li> <li>Grotewold E (2006). <i>The science of flavonoids</i>. New York: Springer. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-387-74550-3.</li> <li>Harborne JB (1967). <a href="https://books.google.com/books?id=CyTf2oObc7cC"><i>Comparative Biochemistry of the Flavonoids</i></a>.</li> <li>Mabry TJ, Markham KR, Thomas MB (1971). "The systematic identification of flavonoids". <i>Journal of Molecular Structure</i>. 10 (2): 320. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1016%2F0022-2860%2871%2987109-0">10.1016/0022-2860(71)87109-0</a>.</li></ul> Wikimedia Commons has media related to Flavonoids. <h3>Databases</h3> <ul><li><a href="https://www.ars.usda.gov/Services/docs.htm?docid=6231">USDA Database for the Flavonoid Content of Selected Foods, Release 3.1 (December 2013); data for 506 foods in the 5 subclasses of flavonoids provided in a separate PDF updated May 2014</a></li> <li><a href="http://bioinfo.net.in/flavodb/home.html">FlavoDB, Bioinformatics Centre, India, November 2019</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>de Souza Farias SA, da Costa KS, Martins JB (April 2021). "Analysis of Conformational, Structural, Magnetic, and Electronic Properties Related to Antioxidant Activity: Revisiting Flavan, Anthocyanidin, Flavanone, Flavonol, Isoflavone, Flavone, and Flavan-3-ol". ACS Omega. 6 (13): 8908–8918. doi:10.1021/acsomega.0c06156. PMC 8028018. PMID 33842761. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8028018" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8028018</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>McNaught AD, Wilkinson A (1997), IUPAC Compendium of Chemical Terminology (2nd ed.), Oxford: Blackwell Scientific, doi:10.1351/goldbook.F02424, ISBN 978-0-9678550-9-7 <a href="978-0-9678550-9-7" target="_blank">978-0-9678550-9-7</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Nič M, Jirát J, Košata B, Jenkins A, McNaught A, eds. (2009). "Flavonoids (isoflavonoids and neoflavonoids)". The Gold Book. doi:10.1351/goldbook. ISBN 978-0-9678550-9-7. Retrieved September 16, 2012. <a href="978-0-9678550-9-7" target="_blank">978-0-9678550-9-7</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>de Souza Farias SA, da Costa KS, Martins JB (April 2021). "Analysis of Conformational, Structural, Magnetic, and Electronic Properties Related to Antioxidant Activity: Revisiting Flavan, Anthocyanidin, Flavanone, Flavonol, Isoflavone, Flavone, and Flavan-3-ol". ACS Omega. 6 (13): 8908–8918. doi:10.1021/acsomega.0c06156. PMC 8028018. PMID 33842761. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8028018" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8028018</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Vitamins and Hormones. Academic Press. 1949. ISBN 978-0-08-086604-8. <a href="978-0-08-086604-8" target="_blank">978-0-08-086604-8</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Clemetson AB (January 10, 2018). Vitamin C: Volume I. CRC Press. ISBN 978-1-351-08601-1. <a href="978-1-351-08601-1" target="_blank">978-1-351-08601-1</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Galeotti F, Barile E, Curir P, Dolci M, Lanzotti V (2008). "Flavonoids from carnation (Dianthus caryophyllus) and their antifungal activity". Phytochemistry Letters. 1 (1): 44–48. Bibcode:2008PChL....1...44G. doi:10.1016/j.phytol.2007.10.001. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Ververidis F, Trantas E, Douglas C, Vollmer G, Kretzschmar G, Panopoulos N (October 2007). "Biotechnology of flavonoids and other phenylpropanoid-derived natural products. Part I: Chemical diversity, impacts on plant biology and human health". Biotechnology Journal. 2 (10): 1214–1234. doi:10.1002/biot.200700084. PMID 17935117. S2CID 24986941. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Zhao DQ, Han CX, Ge JT, Tao J (November 15, 2012). "Isolation of a UDP-glucose: Flavonoid 5-O-glucosyltransferase gene and expression analysis of anthocyanin biosynthetic genes in herbaceous peony (Paeonia lactiflora Pall.)". Electronic Journal of Biotechnology. 15 (6). doi:10.2225/vol15-issue6-fulltext-7. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Spencer JP (May 2008). "Flavonoids: modulators of brain function?". The British Journal of Nutrition. 99 (E Suppl 1): ES60 – ES77. doi:10.1017/S0007114508965776. PMID 18503736. <a href="https://doi.org/10.1017%2FS0007114508965776" target="_blank">https://doi.org/10.1017%2FS0007114508965776</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>"Sources of Flavonoids in the U.S. Diet Using USDA's Updated Database on the Flavonoid Content of Selected Foods" (PDF). Agricultural Research Service, US Department of Agirculture. 2006. <a href="https://www.ars.usda.gov/SP2UserFiles/Place/12354500/Articles/AICR06_flav.pdf" target="_blank">https://www.ars.usda.gov/SP2UserFiles/Place/12354500/Articles/AICR06_flav.pdf</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Oomah BD, Mazza G (1996). "Flavonoids and Antioxidative Activities in Buckwheat". Journal of Agricultural and Food Chemistry. 44 (7): 1746–1750. doi:10.1021/jf9508357. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Levaj B, et al. (2009). "Determination of flavonoids in pulp and peel of mandarin fruits (table 1)" (PDF). Agriculturae Conspectus Scientificus. 74 (3): 223. Archived from the original (PDF) on 2017-08-10. Retrieved 2020-07-31. <a href="https://web.archive.org/web/20170810141820/http://www.agr.unizg.hr/smotra/pdf_74/acs74_38.pdf" target="_blank">https://web.archive.org/web/20170810141820/http://www.agr.unizg.hr/smotra/pdf_74/acs74_38.pdf</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>De Camargo AC, Regitano-d'Arce MA, Gallo CR, Shahidi F (2015). "Gamma-irradiation induced changes in microbiological status, phenolic profile and antioxidant activity of peanut skin". Journal of Functional Foods. 12: 129–143. doi:10.1016/j.jff.2014.10.034. <a href="https://doi.org/10.1016%2Fj.jff.2014.10.034" target="_blank">https://doi.org/10.1016%2Fj.jff.2014.10.034</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Chukwumah Y, Walker LT, Verghese M (November 2009). "Peanut skin color: a biomarker for total polyphenolic content and antioxidative capacities of peanut cultivars". International Journal of Molecular Sciences. 10 (11): 4941–4952. doi:10.3390/ijms10114941. PMC 2808014. PMID 20087468. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2808014" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2808014</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>"Sources of Flavonoids in the U.S. Diet Using USDA's Updated Database on the Flavonoid Content of Selected Foods" (PDF). Agricultural Research Service, US Department of Agirculture. 2006. <a href="https://www.ars.usda.gov/SP2UserFiles/Place/12354500/Articles/AICR06_flav.pdf" target="_blank">https://www.ars.usda.gov/SP2UserFiles/Place/12354500/Articles/AICR06_flav.pdf</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>Chun OK, Chung SJ, Song WO (May 2007). "Estimated dietary flavonoid intake and major food sources of U.S. adults". The Journal of Nutrition. 137 (5): 1244–1252. doi:10.1093/jn/137.5.1244. PMID 17449588. <a href="https://doi.org/10.1093%2Fjn%2F137.5.1244" target="_blank">https://doi.org/10.1093%2Fjn%2F137.5.1244</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> <li id="fn:29"><p>Vogiatzoglou A, Mulligan AA, Lentjes MA, Luben RN, Spencer JP, Schroeter H, et al. (2015). "Flavonoid intake in European adults (18 to 64 years)". PLOS ONE. 10 (5): e0128132. Bibcode:2015PLoSO..1028132V. doi:10.1371/journal.pone.0128132. PMC 4444122. PMID 26010916. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4444122" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4444122</a> <a href="#fnref:29" class="footnote-back-ref">↩</a></p></li> <li id="fn:30"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></p></li> <li id="fn:31"><p>Vogiatzoglou A, Mulligan AA, Lentjes MA, Luben RN, Spencer JP, Schroeter H, et al. (2015). "Flavonoid intake in European adults (18 to 64 years)". PLOS ONE. 10 (5): e0128132. Bibcode:2015PLoSO..1028132V. doi:10.1371/journal.pone.0128132. PMC 4444122. PMID 26010916. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4444122" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4444122</a> <a href="#fnref:31" class="footnote-back-ref">↩</a></p></li> <li id="fn:32"><p>Chun OK, Chung SJ, Song WO (May 2007). "Estimated dietary flavonoid intake and major food sources of U.S. adults". The Journal of Nutrition. 137 (5): 1244–1252. doi:10.1093/jn/137.5.1244. PMID 17449588. <a href="https://doi.org/10.1093%2Fjn%2F137.5.1244" target="_blank">https://doi.org/10.1093%2Fjn%2F137.5.1244</a> <a href="#fnref:32" class="footnote-back-ref">↩</a></p></li> <li id="fn:33"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:33" class="footnote-back-ref">↩</a></p></li> <li id="fn:34"><p>"FDA approved drug products". US Food and Drug Administration. Retrieved November 8, 2013. <a href="http://www.accessdata.fda.gov/scripts/cder/drugsatfda/index.cfm" target="_blank">http://www.accessdata.fda.gov/scripts/cder/drugsatfda/index.cfm</a> <a href="#fnref:34" class="footnote-back-ref">↩</a></p></li> <li id="fn:35"><p>"Health Claims Meeting Significant Scientific Agreement". US Food and Drug Administration. Retrieved November 8, 2013. <a href="https://www.fda.gov/Food/IngredientsPackagingLabeling/LabelingNutrition/ucm2006876.htm#Approved_Health_Claims" target="_blank">https://www.fda.gov/Food/IngredientsPackagingLabeling/LabelingNutrition/ucm2006876.htm#Approved_Health_Claims</a> <a href="#fnref:35" class="footnote-back-ref">↩</a></p></li> <li id="fn:36"><p>EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) (2010). "Scientific Opinion on the substantiation of health claims related to various food(s)/food constituent(s) and protection of cells from premature aging, antioxidant activity, antioxidant content and antioxidant properties, and protection of DNA, proteins and lipids from oxidative damage pursuant to Article 13(1) of Regulation (EC) No 1924/20061". EFSA Journal. 8 (2): 1489. doi:10.2903/j.efsa.2010.1489. <a href="https://doi.org/10.2903%2Fj.efsa.2010.1489" target="_blank">https://doi.org/10.2903%2Fj.efsa.2010.1489</a> <a href="#fnref:36" class="footnote-back-ref">↩</a></p></li> <li id="fn:37"><p>Hensley S (September 7, 2010). "FDA To Lipton: Tea Can't Do That". NPR. Retrieved June 17, 2023. <a href="https://www.npr.org/sections/health-shots/2010/09/07/129701566/fda-to-lipton-tea-can-t-do-that" target="_blank">https://www.npr.org/sections/health-shots/2010/09/07/129701566/fda-to-lipton-tea-can-t-do-that</a> <a href="#fnref:37" class="footnote-back-ref">↩</a></p></li> <li id="fn:38"><p>"Cherry companies warned by FDA against making health claims". The Produce News. November 1, 2005. Retrieved June 17, 2023. <a href="https://theproducenews.com/cherry-companies-warned-fda-against-making-health-claims" target="_blank">https://theproducenews.com/cherry-companies-warned-fda-against-making-health-claims</a> <a href="#fnref:38" class="footnote-back-ref">↩</a></p></li> <li id="fn:39"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:39" class="footnote-back-ref">↩</a></p></li> <li id="fn:40"><p>EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) (2010). "Scientific Opinion on the substantiation of health claims related to various food(s)/food constituent(s) and protection of cells from premature aging, antioxidant activity, antioxidant content and antioxidant properties, and protection of DNA, proteins and lipids from oxidative damage pursuant to Article 13(1) of Regulation (EC) No 1924/20061". EFSA Journal. 8 (2): 1489. doi:10.2903/j.efsa.2010.1489. <a href="https://doi.org/10.2903%2Fj.efsa.2010.1489" target="_blank">https://doi.org/10.2903%2Fj.efsa.2010.1489</a> <a href="#fnref:40" class="footnote-back-ref">↩</a></p></li> <li id="fn:41"><p>Lotito SB, Frei B (December 2006). "Consumption of flavonoid-rich foods and increased plasma antioxidant capacity in humans: cause, consequence, or epiphenomenon?". Free Radical Biology & Medicine. 41 (12): 1727–1746. doi:10.1016/j.freeradbiomed.2006.04.033. PMID 17157175. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:41" class="footnote-back-ref">↩</a></p></li> <li id="fn:42"><p>Williams RJ, Spencer JP, Rice-Evans C (April 2004). "Flavonoids: antioxidants or signalling molecules?". Free Radical Biology & Medicine. 36 (7): 838–849. doi:10.1016/j.freeradbiomed.2004.01.001. PMID 15019969. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:42" class="footnote-back-ref">↩</a></p></li> <li id="fn:43"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:43" class="footnote-back-ref">↩</a></p></li> <li id="fn:44"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:44" class="footnote-back-ref">↩</a></p></li> <li id="fn:45"><p>Hidalgo M, Oruna-Concha MJ, Kolida S, Walton GE, Kallithraka S, Spencer JP, de Pascual-Teresa S (April 2012). "Metabolism of anthocyanins by human gut microflora and their influence on gut bacterial growth". Journal of Agricultural and Food Chemistry. 60 (15): 3882–3890. doi:10.1021/jf3002153. PMID 22439618. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:45" class="footnote-back-ref">↩</a></p></li> <li id="fn:46"><p>Ravishankar D, Rajora AK, Greco F, Osborn HM (December 2013). "Flavonoids as prospective compounds for anti-cancer therapy". The International Journal of Biochemistry & Cell Biology. 45 (12): 2821–2831. doi:10.1016/j.biocel.2013.10.004. PMID 24128857. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:46" class="footnote-back-ref">↩</a></p></li> <li id="fn:47"><p>Manach C, Mazur A, Scalbert A (February 2005). "Polyphenols and prevention of cardiovascular diseases". Current Opinion in Lipidology. 16 (1): 77–84. doi:10.1097/00041433-200502000-00013. PMID 15650567. S2CID 794383. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:47" class="footnote-back-ref">↩</a></p></li> <li id="fn:48"><p>Babu PV, Liu D, Gilbert ER (November 2013). "Recent advances in understanding the anti-diabetic actions of dietary flavonoids". The Journal of Nutritional Biochemistry. 24 (11): 1777–1789. doi:10.1016/j.jnutbio.2013.06.003. PMC 3821977. PMID 24029069. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3821977" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3821977</a> <a href="#fnref:48" class="footnote-back-ref">↩</a></p></li> <li id="fn:49"><p>Ferretti G, Bacchetti T, Masciangelo S, Saturni L (April 2012). "Celiac disease, inflammation and oxidative damage: a nutrigenetic approach". Nutrients. 4 (4): 243–257. doi:10.3390/nu4040243. PMC 3347005. PMID 22606367. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3347005" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3347005</a> <a href="#fnref:49" class="footnote-back-ref">↩</a></p></li> <li id="fn:50"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:50" class="footnote-back-ref">↩</a></p></li> <li id="fn:51"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:51" class="footnote-back-ref">↩</a></p></li> <li id="fn:52"><p>Romagnolo DF, Selmin OI (2012). "Flavonoids and cancer prevention: a review of the evidence". Journal of Nutrition in Gerontology and Geriatrics. 31 (3): 206–238. doi:10.1080/21551197.2012.702534. PMID 22888839. S2CID 205960210. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:52" class="footnote-back-ref">↩</a></p></li> <li id="fn:53"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:53" class="footnote-back-ref">↩</a></p></li> <li id="fn:54"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:54" class="footnote-back-ref">↩</a></p></li> <li id="fn:55"><p>Delage B (November 2015). "Flavonoids". Linus Pauling Institute, Oregon State University, Corvallis, Oregon. Retrieved January 26, 2021. <a href="http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids" target="_blank">http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids</a> <a href="#fnref:55" class="footnote-back-ref">↩</a></p></li> <li id="fn:56"><p>Wang X, Ouyang YY, Liu J, Zhao G (January 2014). "Flavonoid intake and risk of CVD: a systematic review and meta-analysis of prospective cohort studies". The British Journal of Nutrition. 111 (1): 1–11. doi:10.1017/S000711451300278X. PMID 23953879. <a href="https://doi.org/10.1017%2FS000711451300278X" target="_blank">https://doi.org/10.1017%2FS000711451300278X</a> <a href="#fnref:56" class="footnote-back-ref">↩</a></p></li> <li id="fn:57"><p>"Scientific Opinion on the substantiation of a health claim related to cocoa flavanols and maintenance of normal endothelium-dependent vasodilation pursuant to Article 13(5) of Regulation (EC) No 1924/2006". EFSA Journal. 10 (7). June 27, 2012. doi:10.2903/j.efsa.2012.2809. Retrieved June 17, 2023. <a href="https://www.efsa.europa.eu/pt/efsajournal/pub/2809" target="_blank">https://www.efsa.europa.eu/pt/efsajournal/pub/2809</a> <a href="#fnref:57" class="footnote-back-ref">↩</a></p></li> <li id="fn:58"><p>"Cocoa flavanol health claim becomes EU law". Confectionary News. September 4, 2013. Retrieved June 17, 2023. <a href="https://www.confectionerynews.com/Article/2013/09/04/Cocoa-flavanol-health-claim-becomes-EU-law" target="_blank">https://www.confectionerynews.com/Article/2013/09/04/Cocoa-flavanol-health-claim-becomes-EU-law</a> <a href="#fnref:58" class="footnote-back-ref">↩</a></p></li> <li id="fn:59"><p>Kavanaugh C (February 1, 2023). RE: Petition for a Qualified Health Claim – for Cocoa Flavanols and Reduced Risk of Cardiovascular Disease (Docket No. FDA-2019-Q-0806) (Report). FDA. <a href="https://www.fda.gov/media/165090/download" target="_blank">https://www.fda.gov/media/165090/download</a> <a href="#fnref:59" class="footnote-back-ref">↩</a></p></li> <li id="fn:60"><p>Aubrey A (February 12, 2023). "Is chocolate good for your heart? Finally the FDA has an answer – kind of". NPR. Retrieved June 17, 2023. <a href="https://www.npr.org/sections/health-shots/2023/02/12/1156044919/chocolate-heart-health-flavanols" target="_blank">https://www.npr.org/sections/health-shots/2023/02/12/1156044919/chocolate-heart-health-flavanols</a> <a href="#fnref:60" class="footnote-back-ref">↩</a></p></li> <li id="fn:61"><p>Sinha RK (January 2004). Modern Plant Physiology. CRC Press. p. 457. ISBN 9780849317149. <a href="9780849317149" target="_blank">9780849317149</a> <a href="#fnref:61" class="footnote-back-ref">↩</a></p></li> <li id="fn:62"><p>Trantas E, Panopoulos N, Ververidis F (November 2009). "Metabolic engineering of the complete pathway leading to heterologous biosynthesis of various flavonoids and stilbenoids in Saccharomyces cerevisiae". Metabolic Engineering. 11 (6): 355–366. doi:10.1016/j.ymben.2009.07.004. PMID 19631278. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:62" class="footnote-back-ref">↩</a></p></li> <li id="fn:63"><p>Ververidis F, Trantas E, Douglas C, Vollmer G, Kretzschmar G, Panopoulos N (October 2007). "Biotechnology of flavonoids and other phenylpropanoid-derived natural products. Part II: Reconstruction of multienzyme pathways in plants and microbes". Biotechnology Journal. 2 (10): 1235–1249. doi:10.1002/biot.200700184. PMID 17935118. S2CID 5805643. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:63" class="footnote-back-ref">↩</a></p></li> <li id="fn:64"><p>Yisa J (2009). "Phytochemical Analysis and Antimicrobial Activity of Scoparia dulcis and Nymphaea lotus". Australian Journal of Basic and Applied Sciences. 3 (4): 3975–3979. Archived from the original on October 17, 2013. <a href="https://web.archive.org/web/20131017003142/http://connection.ebscohost.com/c/articles/51366872/phytochemical-analysis-antimicrobial-activity-scoparia-dulcis-nymphaea-lotus" target="_blank">https://web.archive.org/web/20131017003142/http://connection.ebscohost.com/c/articles/51366872/phytochemical-analysis-antimicrobial-activity-scoparia-dulcis-nymphaea-lotus</a> <a href="#fnref:64" class="footnote-back-ref">↩</a></p></li> <li id="fn:65"><p>Bello IA, Ndukwe GI, Audu OT, Habila JD (October 2011). "A bioactive flavonoid from Pavetta crassipes K. Schum". Organic and Medicinal Chemistry Letters. 1 (1): 14. doi:10.1186/2191-2858-1-14. PMC 3305906. PMID 22373191. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3305906" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3305906</a> <a href="#fnref:65" class="footnote-back-ref">↩</a></p></li> <li id="fn:66"><p>Delcour JA (1985). "A New Colourimetric Assay for Flavanoids in Pilsner Beers". Journal of the Institute of Brewing. 91: 37–40. doi:10.1002/j.2050-0416.1985.tb04303.x. <a href="https://doi.org/10.1002%2Fj.2050-0416.1985.tb04303.x" target="_blank">https://doi.org/10.1002%2Fj.2050-0416.1985.tb04303.x</a> <a href="#fnref:66" class="footnote-back-ref">↩</a></p></li> <li id="fn:67"><p>Lamaison JL, Carnet A (1991). "Teneurs en principaux flavonoïdes des fleurs de Cratageus monogyna Jacq. et de Cratageus laevigata (Poiret D.C.) en fonction de la végétation" [Principal flavonoid content of flowers of Cratageus monogyna Jacq. and Cratageus laevigata (Poiret D.C.) dependent on vegetation]. Plantes Medicinales: Phytotherapie (in French). 25: 12–16. <a href="#fnref:67" class="footnote-back-ref">↩</a></p></li> <li id="fn:68"><p>Khokhlova, Kateryna; Zdoryk, Oleksandr; Vyshnevska, Liliia (January 2020). "Chromatographic characterization on flavonoids and triterpenes of leaves and flowers of 15 crataegus L. species". Natural Product Research. 34 (2): 317–322. doi:10.1080/14786419.2018.1528589. ISSN 1478-6427. PMID 30417671. <a href="https://pubmed.ncbi.nlm.nih.gov/30417671/" target="_blank">https://pubmed.ncbi.nlm.nih.gov/30417671/</a> <a href="#fnref:68" class="footnote-back-ref">↩</a></p></li> <li id="fn:69"><p>Passicos E, Santarelli X, Coulon D (July 2004). "Regioselective acylation of flavonoids catalyzed by immobilized Candida antarctica lipase under reduced pressure". Biotechnology Letters. 26 (13): 1073–1076. doi:10.1023/B:BILE.0000032967.23282.15. PMID 15218382. S2CID 26716150. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:69" class="footnote-back-ref">↩</a></p></li> </ol>