Alpha-Glucosidase Inhibitor Activity Test of Fractions and Isolate from Leaves of Tristaniopsis obovata

Diabetes mellitus is a metabolic disease characterized by an uncontrolled increase of blood glucose levels. Diabetes drugs such as metformin, acarbose, and others have the side effects that can harm to the human body such as liver, kidneys and other organs. Tristaniopsis obovata Benn. leaves have efficacy as an α-glucosidase inhibitors (AGIs), but the active compounds contained in T. obovata leaves have not been disclosed. This study aimed to determine the active compound in 70% ethanolic extract of T. obovata leaves which has the potential as AGIs. T. obovata leaves were macerated using 70% ethanol for 3×24 h gave ethanol extract-T. obovata leaves in 22.7% yield. Analysis of total phenolic and flavonoid contents of ethanol extract-T. obovata leaves showed that its total phenolic content was 31.1 mg GAE g−1 and total flavonoid content was 10.9 mg QE g−1. Solvents partition of ethanol extract gradually gave n-hexane, ethyl acetate, methanol, and water fractions in 10.0, 32.3, 41.0, and 8.9% yields, respectively. In vitro bioassay of extract and its fractions for α-glucosidase enzyme showed that the IC50 values were 3.2, 3.9, 5.1 and 7.5 µg mL−1 for n-hexane fraction, ethyl acetate fraction, methanol fraction and water fraction, respectively, of ethanol extract. Separation of methanol fraction by column chromatograph using silica gel and n-hexane/ethyl acetate/methanol (4/1/0 - 0/1/1) as a mobile phase produced 17 subfractions (F-1 to F-17). In vitro bioassay of F-11, F-15, and F-16 for α-glucosidase enzyme gave the IC50 values of 40.0, 5.0, 3.6 µg mL−1, respectively. Analysis by FT-NMR spectroscopy, it was predicted that F-16 was myricetin 3-O-α-rhamnoside, which was the first time found in the T. obovata. © 2024, Friends Science Publishers. All rights reserved.