Flavonoids - A Comprehensive Study PDF

FLAVONIDS Dr. Yasmin Alaa Introduction Phenolic compound Non nitrogenous universal plant pigments Composed of OH group attached to an aromatic ring A broad range of compounds – found in all plant ornangs : leaves, fruits, flowers, etc. Comprised of many subclasses: flavonoids, tannins, lignin...

FLAVONIDS Dr. Yasmin Alaa Introduction Phenolic compound Non nitrogenous universal plant pigments Composed of OH group attached to an aromatic ring A broad range of compounds – found in all plant ornangs : leaves, fruits, flowers, etc. Comprised of many subclasses: flavonoids, tannins, lignin etc Introduction Water soluble pigments Plant benefits: - used by vegetative plants for their growth and defense against plaques. Flavonoids protects plant from different biotic and abiotic stresses and act as unique UV filters, function as signal molecules, detoxifying agent and antimicrobial defensive compound. Distribution of flavonoids Absent in algae except member of green algae Present in fungi (Aspergillus candidus) Present everywhere in higher plants. Found throughout the flowering plants. Within plants they are present in: Fruits: berries, grapes, apple, bell peppers, citrus fruits. Beans: soyabeans, legumes Leaves: tea, gingko Roots and rhizomes: Glycyrrhiza Stem: onions Flavonoids They were originally referred to as Vitamin P, likely due to the effect they had on permeability of vascular capillaries, but this term is rarely used now. The flavonoids are polyphenolic compounds possessing 15 carbon atoms; 2 benzene rings joined by a linear 3 carbon chain. The variation in the state of oxidation of the connecting C3 moiety determines the property and class of such compounds. Flavonoids Occurs in plants as glycosides in which 1 or more of the phenolic OH groups are combined with sugar residue. The OH group are found in positions 5 and 7 in ring A, while in ring B commonly carries OH group. Flavonoids consist of aromatic ring A, condensed to heterocyclic ring C attached to second aromatic ring B. Biosynthesis: phenylpropanoid pathway. Starting material : 4- coumaroyl CoA General Uses Flavonoids can bind to several receptors, so they have wide range of biological activities. Pharmacological activities: less specific & less potent than alkaloids or steroids. Antioxidant Colouring agent Nutraceuticals, pharmaceutical, medicinal and cosmetics applications. Flavonoids shows anti-inflammatory activities. They are also found to possess antiviral activity against poliovirus. Flavonoid also exert antibacterial activity against various pathogenic bacteria. Properties of flavonoids Occur in both aglycone and glycoside (O- and C- glycosides) from Mostly are monomeric but dimeric and oligo or polymeric structures (proanthocyanidins) are also known. Classification of flavonoids Flavonoids can be classified on basis of: Saturation of ring C Position of ring B (most prevalent) Molecular weight (least used) Classification of flavonoids - Saturation of ring C When ring C is Saturated Classification of flavonoids - Saturation of ring C When ring C is unsaturated Flavones Flavonols Isoflavones anthocyanidin Classification of flavonoids - Position of ring B Simple flavonoids (ring B attached to 2nd position of ring c), known as 2-phenylbenzopyran: flavans, flavanones, flavones, flavonols. Isoflavonoids (ring B attached to 3rd position of Ring C), known as 3-phenylbenzopyran: isoflavan, isoflavone, isoflavanol, isoflavanones. Neoflavonoids (ring B attached to 4th position of Ring C), known as coumarins Chalcones: nonheterocyclic ring but an open ring system. Benzopyran nucleus is absent. Precursor for other flavonoids. Medicinal & health benefits of flavonoid  Chemical tests 1. All flavonoids + AlCl3 ➔ yellow color + UV light ➔ different fluorescence’s 2.All flavonoids + Pb sub acetate ➔ yellowish ppt 3. Flavanones & flavonols (Alcoholic solution) + Mg / HCl ➔ orange, red or violet (Shinoda's test). 4. Chalcones (Alcoholic solution) + SbCl5/ CCl4 ➔ red or violet. 5.Chromatography (PC & / or TLC) 1. Flavones glycosides  Flavones Name/Structure Chemical uses reaction Diosmin (Barosmin) … cold acid hydrolysis Reduces Capillary fragility , prophylactic& treatment of varicose veins & Diosmetin + Rutinose acute hemorrhoids. Daflon®, … enzyme hydrolysis Diosmetin -7-glucoside + From Buchu, Conium & Dahlia. Rahmnose Apiin Diuretic, antispasmodic … cold acid hydrolysis Apigenin + Apiose-glucose From Parsley, Celery, Roman chamomile Buck Wheat (RUTIN) Source: powder of dried food grains of Fagopyrum esculentum Family: Polygonaceae Constituents: 12% protein, 2% fat, mainly RUTIN Rutin is microcrystalline greenish yellow tasteless powder, soluble in methanol-isopropyl alcohol-pyridine- alkali hydroxides Use: capillary bleeding along with increased capillary fragility so used in retinal haemorrhage CRANBERRY (QUERCETIN) Source: berries of Vaccinium macrocarpon Family: Ericaceae Constituents: Proanthocyanidins, flavonols and anthocyanins, Quercetin Use: Reduction in urinary tract infection, Atherosclerosis, CVS disorders Ovarian cancer Antiviral, antispasmodic &diuretic.  Acylated flavonol Glycosides from Gingko biloba Standardized extract of Gingko biloba leaf is used in treatment of cerebrovascular insufficiency & poor arterial circulation. Ginko biloba glycosides are acylated with p-coumaric acid at C-6 of the glucose moiety. 3. Flavanone glycosides General characters Flavanones have a reactive C=O: with hydroxylamine ➔ oximes (c.f. from flavones). On treatment with alkalis: flavanones ➔ chalcones ➔ flavones. In presence of acid: chalcones ➔ flavanones. Alkali Alkali Flavanone Chalcone Flavone H+ ✓ Hesperidin Uses: Hesperidin is necessary for the absorption of vitamin C & it reduces capillary fragility OMe OMe Rutinose-O O Rutinose-O OH OH OH alkali methylation OH O OH O acid Hesperidin Hesperidin Hesperidin chalcone methyl chalcone ✓ reduce dark circles under the eyes in cosmetic preparations ✓ anti-inflammatory effect  Chalchones Hesperidin methyl chalcone uses ✓reduce dark circles under the eyes in cosmetic preparations ✓anti-inflammatory effect Di hydro-Chalcones Flavanone glycosides-Liquiritin- (Liquiritigenin-4’-glucoside) Source Licorice roots & rhizome Main constituents of DGL (Deglycyrrhizinated Licorice extract) almost free from Glycyrrhizin (triterpenoid saponin of licorice) Uses Liquiritin & its aglycone are used in gastric & duodenal ulcers, & as antiinflammatory. LIQUORICE (BIOFLAVONOIDS) Source: dried roots and stolons of Glycyrrhiza glabara Family: Leguminosae Constituents: Glycyrrhizoflavone, Isocoflavonol, Licochalcone Use: Liver protective, Bioflavonoids have been shown in recent years to have a wide range of biological activities, including cardiovascular, antioxidant, anti-inflammatory, anti-allergic, detoxicant and antimicrobial, etc. Licorice flavonoids are among the strongest antioxidant and anti-ulcer substances so far discovered. GARCINIA (BIOFLAVONOIDS) Source: Dried de-seeded fruits of Garcinia cambogia Family: Guttiferae GS: Western Ghat, Nilgiri, Srilanka Constituent: Biflavonoids, Hydroxy citric acid Use: Flavonoids reported to lower the lipid levels so used in obesity and hypercholestermia The content of bioflavonoids in the plant, which may increase the level of testosterone, which can stimulate erythropoiesis in humans hence increase RBC 5. Isoflavonoid glycosides-  Isoflavonoid glycosides- Daidzin & Genistin Pharmacological action & uses Isoflavones are considered as dietary phytoestrogens. They are cancer-protective, effective in preventing breast & prostate cancer. They also aid in the treatment of osteoporosis. Daidzin is used as antioxidant. SOYBEAN (ISOFLAVONES) Source: dried seeds of Glycine max Family: Leguminosae Constituents: Isoflavones Use: Soy flavonoids (isoflavones) can also reduce blood cholesterol and can help to prevent osteoporosis. Soy flavonoids are also used to ease menopausal symptoms. CVS, Mental and Women's health, cancer prevention Flavonoid-containing compounds Flavonolignans - Silymarin O CH2OH HO O O Oxeran ring OH OH OH O OCH3 Taxifolin Coniferyl alcohol Silybin O OH HO O OCH3 CH2OH OH OH O Silychristin Flavonoid-containing compounds Flavonolignans-Silymarin Source Silybum marianum fruits Structure Silymarin is a mixture of various flavanonol & flavonol derivatives Main components of silymarin are: silybin, silychristin & silydianin Uses Hepatoprotective prophylactic in: Liver damage caused by metabolic toxins. Liver dysfunction after hepatitis. Chronic degenerative liver conditions, e.g. liver cirrhosis & fatty liver. The oxeran ring is responsible for the antihepatotoxic effect of silybin, opening of this ring results in loss of activity.