Identification of α- glucosidase inhibiting natural products from Macaranga capensis and Sapium integerrimum

Abstract

This thesis describes the results obtained from the phytochemical studies of Macaranga capensis and Sapium integerrimum as summarized below. Chemical investigation on the α-glucosidase inhibiting crude methanolic extract of Macaranga capensis resulted in the isolation of two natural products: 3α-hydroxyaleuritolic acid 2-p-hydroxybenzoate (86) and 3-acetoxyoleanolic acid (87) which are related to the class of triterpenoids. Both natural products were isolated for the first time from this plant. The structures of these compounds were elucidated with the aid of NMR spectroscopic data. Both compounds were assayed against α-glucosidase inhibition. Compound (86) exhibited moderate activity in this bioassay with the IC50 value of 2.17mM. Whereas, compound (87) could not be tested as it was only soluble in chloroform and precipitated out in buffer solution. Phytochemical investigation on the ethyl acetate extract of Sapium integerrimum resulted in the isolation of three known compounds; phorbol ester 12-(2’-N-methylaminobenzoyl)-4β,5,20- trideoxyphorbol-13-acetate (113), Quercetin-3-O-α-rhamnopyranoside (114) and scopoletin (115). Compounds 113, 114 and 115 showed good to moderate α-glucosidase inhibitory activity with the IC50 values of 0.57, 0.74 and 1.12 mM, respectively.