Purpose: To investigate the antioxidant properties of the methanol extract of S. tenuifolia as well as its effect on inducible nitric oxide synthase (iNOS) and cycleooxygenase-2 (COX-2) expression in lipopolysaccharides (LPS)-induced cell damage in macrophage cells.

Methods: The antioxidant activities of the plant extract were explored by measuring free radical scavenging activity, viz, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and nitric oxide (NO), and deoxyribose oxidation levels. The mechanism of antioxidant action of the extract was determined by Western blot analysis for iNOS and COX-2 expression in LPS-stimulated RAW 264.7 cells.

Results: The extract contained antioxidant components, including phenolics, flavonoids and anthocyanin and exerted significant radical scavenging activity in a dose-dependent manner. It also produced deoxyribose oxidation and dramatic reducing power. Production of iNOS induced by LPS was significantly inhibited by the extract, suggesting that the extract inhibits nitric oxide (NO) production by suppressing iNOS expression. However, COX-2 induced by LPS was not significantly affected by the extract.

Conclusion: These results suggest that the methanol extract of S. tenuifolia exerts significant antioxidant activity via inhibition of  free radicals, iNOS and DNA oxidation.