Assessment of free radical scavenging activities and antioxidative potential of the tuber extracts of Stemona tuberosa Lour.

Abstract

This study evaluates the phytochemical constituents, free radical scavenging activities and antioxidative potential of the tuber extracts of Stemona tuberosa (ST). The preliminary phytochemical screening revealed the presence of alkaloids, cardiac glycosides, saponins, steroids, tannins and terpenoids from various solvent extracts of ST. The methanolic extract of ST showed the highest phenolic (715.20 ± 2.42 mg GAE/g dry extract) and flavonoid (3864.25 ± 7.54 mg quercetin/g dry extract) contents. S. tuberosa extracts were analyzed for their scavenging activities based on 1,1-diphenyl-2picrylhydrazyl (DPPH), 2, 2’-azino-bis-(3ethylbenzothiazoline-6-sulfonic acid (ABTS), and superoxide anions (O2 ·-) in a cell free system. Different extracts of ST inhibited the generation of DPPH, ABTS and O2 in a concentration dependent manner. Among the various extracts of ST, the methanolic extract showed the highest scavenging activities for ABTS and O2 ·with IC50 of 36.20 ± 0.832 μg/ml and 98.93 ± 3.37 μg/ml respectively. The scavenging activity of methanolic extract for ABTS and O2 ·was significantly higher than the standard ascorbic acid. However, chloroform extract was found to possess the highest scavenging activity for DPPH with IC50 of 7.36 ± 0.081 μg/ml. The total reducing power of ST extracts was also determined by measuring the transformation of Fe3+ into Fe2+ and the methanolic extract was found to exhibit the highest reducing power. The extracts were also analyzed for their anti-haemolytic activity and inhibitory effect on lipid peroxidation in an ex vivo condition using mice erythrocyte and liver, respectively. The antihaemolytic activity of ST extracts also increased with the increase in concentration of the extract. Chloroform extract was found to possess the highest anti-haemolytic activity with 68.81 % inhibition followed by methanolic extract (38.57 %) and aqueous extract (20.81 %). Methanolic extract showed the highest inhibitory activity on lipid peroxidation (80.5 %) followed by chloroform extract (67.8 %) and then aqueous extract (62.63 %). Our study suggests that ST extracts have free radical scavenging and antioxidative potential, probably due to their high phenolic and flavonoid contents.