Abstract

The methanol, ethanol, acetone, and water extracts of six Vietnamese medicinal plants,Premna integrifolia, Terminalia nigrovenulosa, Pseuderanthemum palatiferum,Streptocaulon juventas, Eclipta alba (L), and Solanum hainanense were investigated for their antioxidant and radical scavenging activities using reducing power, metal chelating activity, and 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) assays. Extraction yields, total phenolic and flavonoid contents of methanol extracts were higher than those of other solvent extracts. These results were also similar to reducing power and radical scavenging activities of extracts of T. nigrovenulosa and P. integrifolia. However, the highest metal chelating activity was found in methanol and water extracts of S. juventas, and methanol extract of E. alba. The methanol extracts of T. nigrovenulosa (bark and leaves) and P. integrifolia leaves, which were found to have high anti-radical capacities and reducing power, and those of S. juventas and E. alba, with their high metal chelating activity, have significant potential for use as natural antioxidants.

Key words: Medicinal plants, polyphenol, antioxidant activity, radical scavenging.