FREE RADICAL SCAVENGERS FROM DENDROBIUM PALPEBRAE

Abstract

Phytochemical study of Dendrobium palpebrae Lindl. (Orchidaceae) afforded ten pure compounds. One of them was characterized as a new phenanthrene-phenanthraquinone derivative named dendropalpebrone, and nine known compounds were identified as gigantol, lusianthridin, nobilone, 3,7-dihydroxy-2,4,8-trimethoxyphenanthrene, 2,5-dihydroxy-4,9-dimethoxyphenanthrene, moscatilin, scoparone, 4,5,4'-trihydroxy-3,3'-dimethoxybibenzyl and dendroflorin. All of the isolated compounds were initially screened for their free radical scavenging activity via oxygen radical absorbance capacity assay, DPPH radical scavenging assay, deoxyribose degradation assay, and assay for intracellular antioxidant activity in H2O2-induced RAW 264.7 murine macrophage cells. Dendroflorin showed the most potent activity in all assays, especially in the deoxyribose degradation assay. It manifested an IC50 value of 193 µM approximating to the IC50 of Trolox®, a positive control (IC50 160 µM). In a further evaluation, dendroflorin significantly reduced reactive oxygen species in hydrogen peroxide induced RAW 264.7 macrophage cells in a dose-dependent manner, and it also improved the activity of cellular antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT).