INHIBITORY ACTIVITY OF THE ACTIVE COMPOUND OF ETHYL ACETATE FRACTION OF TAMOENJU (Hibiscus surattensis L.) LEAVES AGAINST α-GLUCOSIDASE AND DIPEPTIDYL PEPTIDASE-4 ENZYMES

Abstract

The ethyl acetate fraction (EAF) of tamoenju (Hibiscus surattensis L.) leaves, used as a traditional antidiabetic agent in Central Sulawesi, has high inhibitory activity against α-glucosidase and dipeptidyl peptidase-4 (DPP-4). The aim of this study was to isolate the active compound of EAF that was carried out by step gradient polarity extraction, then separated and purified by chromatography. The structure was identified and characterized using NMR spectroscopy and LC-MS. α-glucosidase inhibitory activity was evaluated using the in vitro standard α-glucosidase inhibition test, while DPP-4 activity was evaluated by ex vivo DPP-4 inhibitor test using rat blood serum as the enzyme source. IC50 values were determined by nonlinear regression curve and fit using GraphPad Prism 8 and were expressed as mean ± SEM. In this research, we obtained the isolated compound was identified as kaempferol, which was isolated for the first time from this plant. The isolate exhibited potent α-glucosidase and DPP-4 inhibition with IC50 values of 27.78 ± 0.86 and 7.37 ± 0.06 μg/mL, respectively. Acarbose and sitagliptin as positive control had IC50 values of 17.80 ± 0.27 and 25.56 ± 0.43 μg/mL, respectively. The isolate level by LC-MS was estimated to be 182.23 mg/g isolate. Therefore, tamoenju leaves have great potential as functional foods and in the development of antidiabetic drugs. Keywords: α-Glucosidase, Antidiabetic, Dipeptidyl peptidase-4, Kaempferol, Tamoenju, Hibiscus surattensis L