Flavonoids are a group of natural substances found in plant parts including fruits, grains, bark, roots, stems, ﬂowers, etc. They can also be obtained from beverages and wine amongst others. Specific examples include broccoli, grapefruit, pomegranate, soybeans, green tea, skullcap, tomatoes, cherries, apples, etc. They are the most abundant polyphenols in the human diet as they account for about two-thirds of all ingested polyphenols. This flavonoid class has a wide variety of characteristics in higher plants. Many ﬂavonoids are easily recognized as ﬂower pigments in most flowering plants having seeds in fruits. However, their occurrence is not restricted to ﬂowers as they are found in all parts of plants (Dewick, 2002).
These natural products are well known for their beneﬁcial effects on health due to their broad biological activities such as anti-oxidative, anti-inﬂammatory, anti-mutagenic, anti-carcinogenic, anti-hepatoprotective, antihypertensive, immune-boosting and antidiabetic activities amidst others, etc.
Source: (Panche et al., 2016)
Flavonoids can be classified into flavones (apigenin, luteolin, chrysin, baicalein, baicalin), flavonols (quercetin, kaempferol, myricetin, galangin, fisetin), flavanols (epicatechin gallate, theaflavin, epigallocatechin), anthocyanins (delphindin, cyanidin, malvidin, pelargonidin, peonidin), flavanones (naringenin and hesperetin) and isoflavones (genistein, glycitein, formononetin, daidzein).
Flavonoids subclasses and examples
Source: Aboody & Mickymaray (2020)
Flavonols can be found in onions, apples, romaine lettuce, tomatoes, garbanzo beans, turnip greens, sweet potatoes, etc. Flavanols (chalcones) are found in apples, bananas, blueberries, peaches, pears, strawberries, etc. Flavones are found in apples, oranges, watermelon, chili peppers, lettuce, etc. Flavanones are found in oranges, grapefruit, lemons, tomatoes, etc. Anthocyanins are found in blueberries, raspberries, eggplant, black rice, red cabbage, etc. Isoflavonoids are found in soybean, chickpea, lupin seed products, etc.
Flavonoids subclasses and food sources
- Panche, A. N., Diwan, A. D., & Chandra, S. R. (2016). Flavonoids: an overview. Journal of nutritional science, 5.
- Dewick, P. M. (2002). Medicinal natural products: a biosynthetic approach. John Wiley & Sons.
- Aboody, M. S. A., & Mickymaray, S. (2020). Anti-fungal efficacy and mechanisms of flavonoids. Antibiotics, 9(2), 45.
- Cushnie, T. T., & Lamb, A. J. (2005). Antimicrobial activity of flavonoids. International journal of antimicrobial agents, 26(5), 343-356.