α-Glucosidase inhibitor produced by an endophytic fungus, Xylariaceae sp. QGS 01 from Quercus gilva Blume

Xylariaceae sp. QGS 01, an endophytic fungus isolated from the stem of Quercus gilva Blume showed high α-glucosidase inhibitory activity. α-Glucosidase inhibitor have the role as one of carbohydrate-hydrolyzing enzymes to postpone absorption of glucose in the digestive organs. The α-glucosidase inhibitor constituents were isolated from the ethyl acetate extract of the mycellium of endophytic fungi Xylariaceae sp. QGS 01 using a bioassay-guided fractionation technique. Further separation and purification of the active fraction led to the isolation of constituents with strong inhibitory activities against α-glucosidase: 8-hydroxy-6,7-dimethoxy-3-methylisocoumarine (1) with inhibitory concentration (IC₅₀) values against α-glucosidase from Saccharomyces cerevisiae of 41.75 μg/mL, while quercetin as the standard had an IC₅₀ value of 4.80 μg/mL. The results of the present study showed that the endophytic fungus Xylariaceae sp. QGS 01 is potentially a rich source of antidiabetic medicine.