ABSTRACT
Melinjo (Gnetum gnemon L.) is distributed in Southeast Asia and its fruits, seeds and leafs are commonly eaten in Indonesia. It was found that melinjo seed extract contains some resveratrol dimers (gnetin C, gnemonoside A and gnemonoside D). Melinjo seed extract and gnetin C have been reported to show beneficial effects on several diseases, such as hyperuricemia, atherosclerosis, fatty liver, diabetes, dementia, cancer, skin aging and periodontitis etc．Melinjo seed extract is one of the desired functional food materials in Japan.
ABSTRACT
Objective] To explore a new method of synthesis of resveratrol oligmer induced by photosensitizers, further analyze its free radical scavenging activity and analgesic activity. [Method] Resveratrol was dispersed in pH 7.4 phosphate buffer solution, mixed with pheophorbide, then illuminated by laser at 630nm. The oligmers in the filtrate were analyzed by HPLC-MS and isolated by preparative liquid chromatography. Free radical scavenging activity was determined by DPPH and ABTS method, and the analgesic effect was measured by hot plate test and acetic acid writhing test in mice. [Result] A new peak occurred and reached stable in reactive solution after 20 min illumination. It was identified as the dimer of resveratrol with conversion of 35%. Its concentrations on inhibition of 50% DPPH and ABTS radical were respectively 230 μg·mL-1 and 273 μg·mL-1. It reached maximum pain threshold at 180 min, and the inhibition rate of writhing number was 62.6% with better effects than resveratrol. [Conclusion] Reseratrol can be polymerized to the dimer after pheophorbide excited by red light, the resveratrol and its dimer both have the ability of eliminating free radicals and analgesic effects, but the dimer has the stronger activity.