Antioxidant activity of Indian propolis and its chemical constituents

We report for the first time the antioxidant activity of the aqueous and ethanol extracts of Indian propolis (AEP and EEP, respectively). The antioxidant activity was measured by chemical and electrochemical assays. Reducing power and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were the chemical assays, whereas, cyclic voltammetry was used as the electrochemical assay. In all these assays, AEP showed significantly greater activity over EEP; which is in contradiction with the previous reports of propolis from other countries. This may be due to its higher polyphenol content. Hence aqueous extract may well be a substitute of organic solvent extracts of propolis. Moreover, two flavonoids, pinocembrin (1) and galangin (2) were isolated from EEP; among which (2) showed high DPPH radical scavenging activity. Thus Indian propolis, being a rich source of natural antioxidants, may be used in the prevention of various free radicals related diseases.