Flavonoids in Biological System BY Dr. Gobinath Pandian

ABOUT FLAVONOIDS INTRODUCTION STRUCTURE PROPERTIES SOURCE TYPES SYNTHESIS ROLE BIOLOGICAL EFFECTS

INTRODCTION The Flavonoids are most commonly known for their antioxidant activity. Flavonoids are "the most common group of polyphenolic compounds in the human diet and are found ubiquitously in plants. They are secondary metabolites, meaning they are organic compounds that have no direct involvement with the growth or development of plants. Flavonoids are becoming very popular because they have many health Promoting effects. For examples : anti-allergic, anti-cancer, antioxidant, anti-inflammatory and anti-viral. Nutrition experts recommend eating flavonoid-rich foods rather than taking dietary supplements containing large amounts of flavonoids.

Structure and Properties Flavonoids are water soluble polyphenolic molecules containing 15 carbon atoms. Flavonoids belong to the polyphenol family. Flavanoids can be visualized as two benzene rings which are joined together with a short three carbon chain. One of the carbons of the short chain is always connected to a carbon of one of the benzene rings, either directly or through an oxygen bridge, thereby forming a third middle ring, which can be five or six-membered. The flavonoids consist of 6 major subgroups: chalcone, flavone, flavonol, flavanone, anthocyanins and isoflavonoids. Together with carotenes, flavanoids are also responsible for the coloring of fruits, vegetables and herbs.

Structural difference Iso-flavones Flavonols Flavones Flavanones Flavanols Anthocyanidins

Source Flavonoids are found in most plant material. The most important dietary sources are fruits, tea and soybean. Green and black tea contains about 25% percent flavonoids. Other important sources of flavonoids are apple (quercetin), citrus fruits (rutin and hesperidin),

Major food sources for Flavanoids The Fruits:

Types/List of Flavonoids Flavonoids, a subclass of polyphenols, are a group of phytochemicals that are among the most potent and abundant antioxidants in our diet. FLAVONOLS: myricetin and quercetin FLAVONES: apigenin and luteolin FLAVANONES: hesperetin and naringenin FLAVAN-3-OLS: catechin, epicatechin, epicatechin gallate, epigallocatechin, epigallocatechin gallate ANTHOCYANIDINS: cyanidin, delphinidin, malvidin, pelargonidin, peonidin

Common Dietary Flavonoids Flavonoid Subclass Dietary Flavonoids Some Common Food Sources Anthocyanidins Cyanidin, Delphinidin, Malvidin, Pelargonidin, Peonidin, Petunidin Red, blue, and purple berries; red and purple grapes; red wine Flavanols Monomers (Catechins): Catechin, Epicatechin, Epigallocatechin, Epicatechin gallate, Epigallocatechin gallate Dimers and Polymers: Theaflavins,Thearubigins, Proanthocyanidins Catechins: Teas (particularly green and white), chocolate, grapes, berries, apples Theaflavins, Thearubigins: Teas (particularly black) Proanthocyanidins: Chocolate, apples, berries, red grapes, red wine Flavanones Hesperetin, Naringenin, Eriodictyol Citrus fruits and juices, e.g.,oranges, grapefruits, lemons Flavonols Quercetin, Kaempferol, Myricetin, Isorhamnetin Widely distributed: yellow onions, scallions, kale, broccoli, apples, berries, teas Flavones Apigenin, Luteolin, Tangeritin Parsley, thyme, celery, hot peppers, Isoflavones Daidzein, Genistein, Glycitein Soybeans, soy foods, legumes

Structural difference Iso-flavones Flavonols Flavones Flavanones Flavanols Anthocyanidins

General biosynthetic pathway of FLAVONOIDS SYNTHESIS General biosynthetic pathway of FLAVONOIDS Flavonoids are synthesized by the phenylpropanoid metabolic pathway in which the amino acid phenylalanine is used to produce 4-coumaroyl-CoA. This can be combined with malonyl-CoA to yield the true backbone of flavonoids, a group of compounds called chalcones which contain two phenyl rings Along this pathway many products can be formed, including the flavonols, flavan-3-ols, proanthocyanidins (tannins) and a host of other polyphenolics.

Synthesis of Flavonoids

Simplified presentation of Pathway

Role of flavonoids: Flavonoid intake from vegetables, fruit, berries and beverages has been favorably linked with reduced risks of a number of diseases Antioxidants can be called as a natural defence mechanism in living organisms. Antioxidants are molecules which can safely interact with free radicals and terminate the chain reaction before vital molecules are damaged.

Health benefits of Flavanoids Fight against Heart Diseases

Health benefits of Flavanoids Fight against obesity

Health benefits of Flavanoids Fight against Diabetes

Dietary Function of Flavonoids Flavonoids are plant phytochemicals that cannot be synthesized by humans. Dietary intake estimates vary from 23 mg/day to 1000 mg/day have demonstrated that flavonoids have antioxidant and antimutagenic activities.

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