Isolation, identification and α-glucosidase inhibition evaluation of a phenolic compound from Elaeocarpus mastersii King leaves

Abstract

Elaeocarpus mastersii King is an Indonesian folk medicine with high phenolic content. In this study, the E. mastersii King leaves were extracted using methanol solvent through maceration. The methanol extract was continuously fractionated by the liquid-liquid extraction using hexane, dichloromethane (DCM), and ethyl acetate solvents, respectively. The DCM fraction was purified by column chromatography using Silica gel 60 and Sephadex LH-20 as the stationary phase and monitored by thin-layer chromatography. This isolation process led to obtaining a pure compound with the appearance of white crystalline powder and a melting point of 198-199℃. This compound absorbed the UV light at the wavelength of 229 and 274 nm, as well as produced the bathochromic shift by the addition of NaOH reagent indicating the aromatic compound with the hydroxyl (OH) substituent. The IR spectrum confirmed the presence of aromatic and OH groups along with other functional groups, such as carbonyl (vmax 1693 cm-1) and alkane (C-H, vmax 2953 cm-1). The NMR data suggested the isolated compound as methyl gallate. Furthermore, the m/z value of the isolated compound was 185.04416 Da [M+H]+. It confirmed the monoisotopic mass of the methyl gallate (184.0362 Da). However, biological evaluation as an α-glucosidase inhibitor showed no positive activity.