Phytochemical investigation, cytotoxicity and free radical scavenging activities of non-polar fractions of Acalypha hispida (leaves and twigs)

Abstract

Free radicals are involved in the process of lipid peroxidation and play a cardinal role in numerous chronic diseases like cancer, coronary heart disease and ageing. Thus the ability to scavenge free radicals in order to minimize oxidative damage to living cells is very important. The hexane extract of Acalypha hispida (Burn F.) was screened for phytochemical constituents and was found to contain flavonoids, carbohydrates, phenols and alkaloids. Fractions obtained from chromatographic separation were screened for free radical scavenging activities using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and hydrogen peroxide. Out of the sixteen pooled fractions (S ₁-S ₁₆) screened, compounds S ₁₀ (91.8 %), S ₁₁ (93.8 %), S ₁₄ (92.5 %) and S ₁₅ (91.4 %) at a concentration of 0.1 mg/ml had significant antioxidant activities when compared to the known antioxidant ascorbic acid (90.9 %). However, in the analysis using hydrogen peroxide, S ₁ (99.5 %), S ₉ (99.2 %), S ₁₀ (95.4 %),S ₁₁ (95.8 %) and S ₁₅ (95.6 %) gave better activity than ascorbic acid (94.8 %), while only S ₁ and S ₉ were more effective than butylated hydroxylanisole (98.9 %) and α-Tocopherol (99.1 %) at the same concentration. The cytotoxicity analysis using the Brine Shrimp lethality test gave LC ₅₀ values greater than 1000 μg/ml for some of the fractions indicating very low level of toxicity. The better scavenging activity of A. hispida could be linked to the presence of secondary plant products like flavonoids and phenols, which have the ability to scavenge hydroxyl radicals, superoxide anions and lipid peroxy radicals.