Abstract:
α-Glucosidase inhibitors are a group of anti-diabetic drugs that can help control blood sugar levels by hindering the breakdown of oligosaccharides and disaccharides into monosaccharides such as glucose, thus preventing intestinal absorption. Recent studies have shown that several plants in the Orchidaceae family produce secondary metabolites with α-glucosidase inhibitory activity. Rhynchostylis retusa, an orchid traditionally used for treating various diseases such as asthma, diabetes, and obesity, was investigated. The methanol extract of R. retusa showed significant inhibitory activity against the enzyme α-glucosidase, with 85.71% inhibition at a concentration of 100 µg/ml. The objective of this study was to isolate and identify the active constituents of this plant. The extract underwent chromatographic separation, and the isolation of the active compounds proceeded under monitoring by thin-layer chromatography. Five compounds, including gigantol, 9,10-dihydro-5-methoxy-2,3,7-phenanthrenetriol, vanillic acid, vanillin, and p-hydroxybenzaldehyde, were isolated and identified by mass spectrometry and NMR spectroscopy. The bioassay results revealed that 9,10-dihydro-5-methoxy-2,3,7-phenanthrenetriol (IC50 33.46±1.20 µM) and p-hydroxybenzaldehyde (IC50 174.75±21.81µM) possessed stronger inhibitory activity than the positive control acarbose (IC50 552.54±56 µM), whereas the other compounds exhibited no activity.