Quantification of Total Phenolics, Flavonoids and Evaluation of in vitro Free Radical Scavenging Activities in Psidium guajava L.

Abstract

The present study was undertaken to quantify total phenolics and flavonoids and investigate in vitro free radical scavenging activities of leaf extracts of two varieties of Psidium guajava L. viz., Lalit and Allahabad safeda. Leaf extracts of Lalit and Allahabad safeda were prepared by Soxhlet extraction and ethanol extracts were used for in vitro assays. Total phenolic and flavonoid contents, 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), 2,2-diphenyl-1-picrylhydrazyl, nitric oxide and super oxide free radical scavenging activities were determined at 100, 200, 300, 400, 500, 600 and 700 µg/ml concentrations of Lalit and Allahabad safeda leaf extracts. Results indicated the presence of higher phenolic and flavonoid contents in the leaf extract of Lalit compared to that of Allahabad safeda. The leaf extracts of Lalit and Allahabad safeda showed dose-dependent increase in 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), 2,2-diphenyl-1-picrylhydrazyl and nitric oxide radical scavenging activities and a decrease in super oxide radical scavenging activities. However, Lalit showed higher free radical scavenging activity compared to that of Allahabad safeda. Further, the IC50 values of Lalit for DPPH, 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), nitric oxide and super oxide free radicals were 229.56, 503.07, 430.40, 07 and 377.96 µg/ml, respectively. In addition, the IC50 values of Allahabad safeda for 2,2-diphenyl-1-picrylhydrazyl, 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), nitric oxide and super oxide free radicals were, 270.24, 543.63, 469.99 and 515.50 µg/ml, respectively. This study clearly demonstrated antioxidant activity in both the extracts of Lalit and Allahabad safeda. The better antioxidant activity of Lalit extract could be due to the presence of higher phenolic content compared to Allahabad safeda.