Among the four different parts of mulberry (Morus alba L.) tree, ethanol extract of Morus root bark showed the highest α-glucosidase inhibitory activity (IC50=12.01 μg/mL). Bioassay-guided fractionation of the ethanolic extract of root bark by Diaion HP-20, silica gel, ODS-A, and Sephadex LH-20 column chromatographies led to the isolation of four compounds, including Compound (Comp.) 1 (IC50=5.22 μg/mL), Comp. 2 (IC50=1.78 μg/mL), Comp. 3 (IC50=2.94 μg/mL), and Comp. 4 (IC50=1.54 μg/mL) with strong α-glucosidase inhibitory activities. Their chemical structures were elucidated as morusin (Comp. 1), kuwanon H (Comp. 2), chalcomoracin A (Comp. 3), and chalcomoracin B (Comp. 4) by UV and NMR spectral analyses. These results suggest that prenylflavonoid and mulberrofuran of Morus root bark may be useful as potential therapeutic agents for diabetes.

Keywords: Morus root bark, α-glucosidase inhibitors, morusin, kuwanon H, chalcomoracin A & B