Antioxidant oligostilbenoids from the stem wood of Hopea hainanensis

Phytochemical investigation of the stem wood of Hopea hainanensis, a Dipterocarpaceae tree endemic to Hainan Island of China, leads to four new oligostilbenoids, hopeahainols C-F (1-4), and eight known ones (5-12). All of the structures were elucidated by comprehensive analysis of spectroscopic data including UV, IR, MS, and NMR after purification of individual compounds through a combination of chromatographic methods. A resveratrol glucoside, eight resveratrol dimers, two trimers, and a tetramer were identified. All of the polyphenols were tested for their radical scavenging and total reducing capacities by measuring their capacity to scavenge the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, anion superoxide radical, and also to induce the reduction of Mo (VI) to Mo (V). Most of the compounds exhibited potent antioxidant and radical scavenger capacity compared with the positive controls (resveratrol, ascorbic acid, and butylated hydroxyanisole (BHA)) at 0.4 mM concentration.