Inhibitory effect of triterpenoids from the mushroom Inonotus obliquus against α-glucosidase and their interaction: Inhibition kinetics and molecular stimulations.

Bioassay-guided fractionation led to the isolation of a series of triterpenoids (1-46) including 12 new ones (1-12) from the mushroom Inonotus obliquus. The structures of all the compounds were elucidated by spectroscopic analysis as well as by comparison with literature data. Triterpenoids 1-3, 6, 7, 16, 24, 25, 27, 38, 43, 44 and 46 showed strong α-glucosidase inhibition, with IC50 values from 11.5 to 81.8 µM. Their structure-activity relationships were discussed. Inonotusol F (24) showed the strongest inhibitory activity and it presented noncompetitive inhibition against α-glucosidase. Molecular docking and molecular dynamics stimulation further demonstrated that GLU302 and PHE298 were key amino acids for the inhibition of inonotusol F (24) towards α-glucosidase. This study indicates the vital role of triterpenoids in explaining hypoglycemic effect of Inonotus obliquus and provides important evidence for further development and utilization of this mushroom.

Inhibitory Effect of Five Ganoderma Species (Agaricomycetes) against Key Digestive Enzymes Related to Type 2 Diabetes Mellitus.

Ganoderma mushrooms are widely used in clinical therapies and functional foods. The antidiabetic effect of Ganoderma has become a research hot spot in recent decades. To search for a superior antidiabetic Ganoderma extract, five common Ganoderma species (G. lucidum, G. sinense, G. tsugae, G. applanatum, and G. leucocontextum) were investigated. A total of 10 fractions, including a total triterpenes fraction and a crude polysaccharides fraction for each, were prepared for further assays. Activities of α-glucosidase and α-amylase are inhibited dominantly by triterpenes from all five Ganoderma species rather than the polysaccharides. G. lucidum triterpenes inhibits α-glucosidase and α-amylase most significantly with IC50 values of 10.02 ± 0.95 µg/mL and 31.82 ± 4.30 µg/mL. Even more, triterpenes content was positively correlated with anti-α-glucosidase and anti-α-amylase activities. Therefore, triterpenes were considered to be the active compounds in inhibiting α-glucosidase and α-amylase activity. It is hoped that the results will provide more systematic information for the application of Ganoderma in the functional food and traditional medicine industries in the future.