Hypoglycemic properties of Leccinum scabrum - An in vitro study on α-glucosidase and α-amylase inhibition activity

Mushrooms have been demonstrated to produce multiple beneficial effects on human nutrition and health due to a variety of constituents and bioactive compounds they are rich in [1-3]. Among the Boletaceae family, Leccinum scabrum (Bull.) Gray, or “birch bolete”, is recently arousing the interest of researchers, proving to be an attractive species from a nutritional and medicinal point of view. This mycorrhizal, edible mushroom is mainly distributed in deciduous woods of Central Eastern Europe and Scandinavia, where is highly valued in gastronomy. It exhibits notable nutritional value and content of health-promoting compounds, and recent investigations have pointed out its antimicrobial, antioxidant, and cytotoxic properties on cancer cells [4-6]. In light of these interesting findings and since there are still only a few studies on the medicinal properties of L. scabrum, a survey was undertaken to evaluate its possible hypoglycemic effect. Basidiomes powder was extracted using a range of green solvents with different polarity and employing the innovative microwave-assisted extraction (MAE) technique [7]. The obtained extracts were assayed to evaluate their in vitro inhibitory activity on the two main enzymes involved in the carbohydrate digestion process, and thus related to blood glucose levels: α-glucosidase and α-amylase [8,9]. All samples were evaluated for their possible cytotoxic effect on human cells viability, carrying out an in vitro assay on HepG2 cells. In all experiments L. scabrum resulted to be highly effective against α-glucosidase and milder on α-amylase, in which case the half-maximal inhibitory concentration could not be determined. In the former case, the ethyl acetate extract showed the most potent bioactivity, with an IC50 value significantly lower than the reference compound 1-deoxynojirimycin (DNJ). No cytotoxicity on hepatic cells was detected for almost all the assayed extracts. The ethyl acetate extract was further processed by fractionation and subsequent GCMS analysis to characterize its composition. In addition, high-resolution mass spectrometry (HRMS) was also performed to determine non-volatile metabolites as well. The results of this research demonstrate how L. scabrum, a mushroom popular in culinary context, exhibits important medicinal properties and has great pharmacological potential for the treatment of type 2 diabetes.