α-Glucosidase and Aldose Reductase Inhibitory Activities from the Fruiting Body of Phellinus merrillii

The inhibitory activity from the isolated component of the fruiting body Phellinus merrillii (PM) was evaluated against alpha-glucosidase and lens aldose reductase from Sprague Dawley male rats and compared to the quercetin as an aldose reductase inhibitor and, acarbose as an alpha-glucosidase inhibitor. The ethanol extracts of PM (EPM) showed the strong alpha-glucosidase and aldose reductase activities. alpha-Glucosidase and aldose reductase inhibitors were identified as hispidin (A), hispolon (B), and inotilone (C), which were isolated from EtOAc-soluble fractions of EPM. The above structures were elucidated by their spectra and comparison with the literatures. Among them, hispidin, hispolon, and inotilone exhibited potent against alpha-glucosidase inhibitor activity with IC50 values of 297.06 +/- 2.06, 12.38 +/- 0.13, and 18.62 +/- 0.23 mu g/ml,, respectively, and aldose reductase inhibitor activity with IC50 values of 48.26 +/- 2.48, 9.47 +/- 0.52, and 15.37 +/- 0.32 mu g/mL, respectively. These findings demonstrated that PM may be a good source for lead compounds as alternatives for antidiabetic agents currently used. The importance of finding effective antidiabetic therapeutics led us to further investigate natural compounds.