Alpha-glucosidase inhibitory activity of ethanol extract, fractions and purified compounds from the wood of <i>Albizia myriophylla</i>

<p><i>Albizia myriophylla</i> Benth. is a medicinal herb which is used as a traditional remedy for various ailments including diabetes in Thailand. In our continued investigation of the biological activity of <i>A. myriophylla</i>, the ethanol extract, fractions and the isolated compounds from the wood of this plant were evaluated for <i>in vitro</i> α-glucosidase inhibition using spectrophotometric method. The plant ethanol extract and its different fractions possessed α-glucosidase inhibitory activity in a concentration-dependent manner. Dichloromethane fraction of the wood ethanol extract exhibited the highest percent inhibition against α-glucosidase (69.30%) among all fractions. Subsequent α-glucosidase inhibition assay proved that indenoic acid (<b>1</b>), 8-methoxy-7, 3′,4′-trihydroxyflavone (<b>2</b>) and 3,4,7,3′-tetrahydroxyflavan (<b>3</b>) were partially rational for antidiabetic effect of this plant species. Among these compounds, <b>3</b> (IC₅₀ 98.59 μg/mL) exhibited potent inhibition of α-glucosidase, compared with a positive control acarbose (IC₅₀ 125 μg/mL). The inhibitory effect towards α-glucosidase of compounds <b>1</b>–<b>3</b> was reported herein for the first time.