Studies on α-glucosidase, aldose reductase and glycation inhibitory properties of sesquiterpenes and flavonoids of Zingiber zerumbet Smith.

Eight known phytochemicals, four sesquiterpenes and four flavonoids of Zingiber zerumbet were screened against α-glucosidase enzyme, aldose reductase enzyme and antiglycation property under in vitro conditions. The results established kaempferol-3-O-methylether as a potent inhibitor of α-glucosidase enzyme with an IC50 value of 7.88 μM. In aldose reductase enzyme inhibition assay, all the compounds except zerumbone epoxide showed good to excellent inhibition properties. Among these, the flavonoid compounds were found to be potent aldose reductase inhibitors compared with the four sesquiterpenes. In addition, compounds such as α-humulene, kaempferol, kaempferol-3-O-methylether and 3″,4″-O-diacetylafzelin displayed potent antiglycation properties. From overall results, we found that kaempferol and kaempferol-3-O-methylether are potent inhibitors of α-glucosidase enzyme, aldose reductase enzyme and glycation reaction, the three main targets of drugs for the treatment of diabetes and its complications.