Bioassay-guided isolation and identification of antioxidative compounds from the bark of Eugenia polyantha

Eugenia polyantha bark extracts were found to have potential antioxidative activities. This study is an effort to investigate the antioxidative compounds in E. polyantha. In vitro antioxidatve assay were used as guided tools for the isolation of antioxidative compounds. The methanol-water extracts showed the highest level of free radical-scavenging activity (ED50) = 180 microg mL(-1) and protection from beta-carotene bleaching (8.7 microg mL(-1)). The methanol-water (1:1) extracts exhibited strong DPPH scavenging activity and protection against beta carotene bleaching and was subjected to repeated silica gel column chromatography. The n-butanol, acetone and ethyl acetate solubles exhibited the highest antioxidative activities, derivatization was conducted to the isolated antioxidative compounds prior to identification. Catechin, gallic acid and rutin were isolated from those solubles as active compounds present in the Eugenia polyantha bark.