Abstract: The inhibitory effects of trilobatin separated from Lithocarpus polystachyus Rehd on the activities of α-glucosidase and α-amylase were determined and compared with those of the anti-diabetic drug acarbose as a positive control and the type of the enzymatic inhibition on α-amylase was investigated. Also, rutin was used as a positive control to measure the ability of the trilobatin from Lithocarpus polystachyus Rehd to scavenge DPPH free radicals. The results showed that α-glucosidase activity was inhibited remarkably by the trilobatin, and the inhibition was noncompetitive and did not exhibit a significant difference when compared to acarbose. Its inhibition rate against α-amylase, however, was lower than that of acarbose despite of having stronger DPPH free radical scavenging effect than rutin. From these experimental results, a conclusion could be drawn that the trilobatin from Lithocarpus polystachyus Rehd is a potential anti-diabetic compound.

Key words: trilobatin, Lithocarpus polystachyus Rehd, α-glucosidase, α-amylase, diabetes