Designing and Synthesis of Flavonoids Derivatives and Screening of their Antioxidant Activity

Abstract

The flavonoids present in red wine were responsible this low cardiovascular mortality rate. Epidemiologic studies further suggest that dietary flavonoids are useful to control and protect the CHD. The flavonoids are yellow color substance (pigments) and the name given on the basis of Latin term Flavus which means yellow color. Flavonoids are derivatives of benzo-pyrone. Banzopyrone is a group of heterocyclic aromatic oxygen containing compounds. Finely powdered zinc chloride (8.25) was dissolved in glacial acetic acid (18ml)  by heating on sand bath then dry resorcinol (appx.5.5 gm) was added with  continuous  stirring to the mixture at  140⁰C. Antioxidant Screening by hydrogen peroxide scavenging assays. Hydrogen peroxide solution (40 mini moles) was prepared with standard phosphate buffer of pH 7.4. Different concentration of the compound stock solution and 4ml distilled water was added to 0.6 ml of hydrogen peroxide solution. UV absorbance was determined at the wavelength of 230 nm after 10 min with a blank solution containing phosphate buffer without H₂O₂. Take 4 ml different concentration of sample solution and 1ml sodium nitroprusside solution, added and incubated for 2.5 hrs at 37⁰C. After incubation baseline was taken with methanol and 1ml sodium nitroprusside solution as blank solution. Griess reagent and methanol was added immediately before recording of readings. The readings were recorded at 546nm wavelenth. In the series of synthesized and evaluated compounds of Flavanoid electron withdrawing group at position four shows good activity. 2,3-dihydroflavan-3-ol derivatives showed lower activity than that of 3- hydroxyflavone derivatives. The 4-oxo (keto double bond at position 4 of the C ring), especially in association with the J2-J3 double bond, increases scavenger activity by delocalizing electrons, 3-hydroxy group on the C ring generates an extremely active scavenger; the combination of J2-J3 double bond,3-hydroxy group and 4-oxo group appears to be the best combination for potent antioxidant activity.

Keywords: Flavonoids, Antioxidant activity, Hydrogen peroxide scavenging, free radicals