Oleanolic acid - an [alpha] -Glucosidase inhibitory and antihyperglycemic active compound from the fruits of Sonneratia caseolaris

Fruits of Sonneratia caseolaris Linn. have many therapeutic applications in folklore medicine. However, chemical examination and biological activity of its fruit are less studied. During the work on identification of antidiabetic principles from Indian mangrove flora, we noticed moderate intestinal ? -glucosidase inhibitory activity of the methanolic extract of its fruits. Three compounds namely oleanolic acid, ? -sistosterol- ? -D-glucopyranoside and luteolin were isolated and identified from the bioactive methanolic extract. In vitro pre-incubation of crude rat intestinal ? -glucosidase with oleanolic acid showed potent ? -glucosidase inhibitory (IC50 = 15 ? M) activity, however, its inhibitory potential decreased drastically when oleanolic acid was pre-incubated with substrate. In in vivo studies also, pretreatment of rats with oleanolic acid displayed significant (p