γ-Glutamyl-β-phenylethylamine, a novel <i>α-glucosidase</i> and <i>α-amylase</i> inhibitory compound from <i>Termitomyces robustus</i> , an edible Nigerian mushroom

Abstract

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