gamma-Glutamyl-beta-phenylethylamine, a novel alpha-glucosidase and alpha-amylase inhibitory compound from Termitomyces robustus, an edible Nigerian mushroom

Termitomyces species are known edible mushrooms in Nigeria, believed to have exceptional culinary and nutraceutical properties. Methanol extract from fruiting bodies of Termitomyces robustus was evaluated for antidiabetic activity using in vitro alpha-amylase and alpha-glucosidase assays. The isolation and structural elucidation of metabolites from the T. robustus extract afforded five compounds including a new natural product gamma-glutamyl-beta-phenylethylamine 3 and four known phenyl derivatives: tryptophan 1, 4-hydroxyphenylacetic acid 2, 4-hydroxyphenylpropionic acid 4, and phenyllactic acid 5. Structures were elucidated from analyses of spectroscopic data (1 D and 2 D NMR, HRESIMS) and all isolated compounds were tested for alpha-amylase and alpha-glycosidase inhibitory activity. The in vitro assay established crude extract to possess alpha- amylase and alpha-glucosidase inhibition with IC50 of 78.05 mu g/mL and 86.10 mu g/mL, respectively. The isolated compounds compared favourably with the standard drug, acarbose with 10 50 ranging from 6.18-15.08 mu g/mL and 18.28-44.63 mu g/mL for alpha-amylase and glucosidase, respectively.