Comparison of the antioxidant and cytotoxic activities of Phyllanthus virgatus and Phyllanthus amarus extracts.

OBJECTIVE To determine the antioxidant activity and cytotoxicity of Phyllanthus virgatus crude extract compared to Phyllanthus amarus. METHODS Phenolic contents of the hydromethanolic extracts were measured using Folin-Ciocalteu reagent. Antioxidant activity was evaluated by the 2,2-diphenyl-1-picrylhydrazyl hydrate free radical scavenging and antilipid peroxidation assays. Cytotoxicity on human hepatoma HepG2 cells was assessed by trypan blue and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide viability assays. A stereomicroscope was used to observe and photograph the morphology of the cells. Oxygen consumption of the HepG2 cells was measured using a Clark oxygen electrode. RESULTS The extract of P. virgatus, which contained more phenolic compounds than P. amarus extract, had higher cytotoxicity and showed higher free radical scavenging activity and more inhibition of peroxidation in a linoleic acid system. P. virgatus extract conspicuously increased the oxygen consumption of HepG2 cells, while P. amarus extract had little stimulatory effect. CONCLUSION The hydromethanolic extract of P. virgatus had stronger antioxidant and cytotoxic action than P. amarus extract. The stimulation of HepG2 cell respiration by P. virgatus extract suggests the extract alters mitochondrial function; this action could play a role in the cytotoxicity of this plant.