Potential of Sorbus berry extracts for management of type 2 diabetes: Metabolomics investigation of 1H NMR spectra, α-amylase and α-glucosidase inhibitory activities, and in vivo anti-hyperglycaemic activity of S. norvegica

Ethnopharmacological relevance: Berries of Sorbus species have been used to treat type 2 diabetes in many regions in Europe. Aims of the study: To investigate the inhibitory activity of berry extract of Sorbus on the digestive enzymes a amylase and alpha-glucosidase, two important targets for management of blood glucose for type 2 diabetics. Furthermore, to test the anti-hyperglycaemic potential of S. norvegica berry extract in vivo. Materials and methods: 70% acetone berry extracts of 16 Sorbus species were tested in vitro for inhibition of alpha-amylase and alpha-glucosidase. Single berry extracts were analysed by H-1-NMR spectroscopy and principal component analysis to evaluate the chemical profiles of the extracts. The anti-hyperglycaemic effect was evaluated in an oral starch tolerance test in STZ-treated C57BL/6 mice. Results: The lowest IC50 values against alpha-amylase and alpha-glucosidase were obtained with the Sorbus species belonging to the subspecies Aria, which have simple leaves compared to pinnately compound leaves of the other Sorbus species. Species belonging to subspecies Aria grouped together and away from the other Sorbus species in the score plot, indicating a difference in chemistry. Both the carbohydrate- and polyphenol-fraction contributed to the enzyme inhibition. Extract of the most active species, S. norvegica, had anti-hyperglycaemic activity, at a level 36 times lower than clinically used acarbose, corresponding to a needed daily dose of 900 mg extract. Conclusions: Sorbus species of subspecies Aria have the potential to be used for management of type 2 diabetes.