Evaluation of antioxidant activities and total phenolic contents of selected Sudanese medicinal plants

Abstract

Antioxidant activities of methanol and water extracts of Cymbopogon proximus aerial parts, Ocimum basilicum leaves and Tribulus terrestris fruits were evaluated using free radical scavenging activity of 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH) and total antioxidant capacities (TAC) by the phosphomolybdenum method. The total phenolic, flavonoid and tannin contents for these extracts were estimated and thereafter were analyzed for their correlation with antioxidant activities. Correlation analysis between the values of DPPH% and TAC revealed a significant correlation with (r=0.96; P=0.002) indicates the viability of the two models for evaluating antioxidants from medicinal plants. It was also observed that there were strong relationships between antioxidant activities and total phenols with higher values observed with water extract(r=0.994 and r= 0.996) with RSA% and TAC respectively. A significant correlation between total phenolic contents and flavonoids was found with (r=0.996; P=0.000). The study findings revealed that O. basilicum methanol extract of the leaves displayed powerful antioxidant activity in the two assay models with (482.25±0.08mg AA Eq/l ) for TAC and (80±0.01%) for RSA%, followed by the plant water extract, while C. proximus showed moderate activities for its two extracts compared to pyrogallate(PRG) as standard compounds, whereas T. terrestris showed the lowest antioxidant activity. Among screened plant materials, remarkable high phenolic and flavonoid contents were found in O. basilicum leaves methanol extract (14.56±0.071mg Gallic acid Eq/g) and (19.03±0.03 mg Querectin E/g) on the basis of dry matter respectively, which contributed to its high antioxidant activity. These findings may indicate that the plant can provide protection against free radicals induced disorders and oxidative stress.