Abstract

Gambir (Uncaria gambir) and other plants belonging to the genus Uncaria have been used in traditional medicine in southeastern Asia, Africa and South America, and they have been studied widely over the past century. Gambier, the dried leaf extract from gambir is known to have antioxidant properties and some studies have attributed it to the presence of tannins and condensed tannins. The objective of this study was to investigate the potential of commercial gambier on the Indonesian market as a scavenger of reactive free radicals, evaluate its ability to inhibit α-glucosidase and determine the bioactive compound responsible for these activities. An ethanolic extract of commercial gambier was extracted with ethyl acetate. The ethanol and ethyl acetate extracts as well as the aqueous extract after ethyl acetate extraction and residue from ethanol extraction were tested for free radical scavenging activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH). They were also tested for α-glucosidase inhibitory activity. The extracts were then studied using reverse phase HPLC, LCMS and NMR to identify the bioactive compound. It was observed that all the extracts had high activity for DPPH inhibition but moderate activity for inhibiting α-glucosidasein vitro. Apart from the aqueous extract, 92% DPPH inhibition by the extracts was achievable at 30 μg/ml. The ethanol and ethyl acetate extracts had significantly higher (p < 0.01) DPPH inhibitory activity than the aqueous extract.IC₅₀ of the organic extracts and residue ranged between 13.8 to 16.2 μg/ml for DPPH inhibition while that of the aqueous extract was 27.4 μg/ml. With regards to α-glucosidase inhibition, however, IC₅₀ range of 15.2 and 49.5 μg/ml was recorded. Catechin was identified as the major bioactive compound present.

Key words: Uncaria gambir, gambier, DPPH, alpha-glucosidase, HPLC, LCMS, NMR