Chemical Constituents from Mentha haplocalyx Briq. (Mentha canadensis L.) and Their α-Glucosidase Inhibitory Activities

ABSTRACT: Mentha haplocalyx (Mentha canadensis) is widely used as a medicinal plant in traditional Chinese medicine, and the extracts of its aerial parts are found to significantly inhibit the activity of α-glucosidase with an IC(50) value of 21.0 μg/mL. Bioactivity-guided isolation of the extracts afforded two new compounds (1 and 2), together with 23 known ones (3–25). Their structures were established by extensive spectroscopic analyses (1D and 2D NMR, MS, IR and UV). Compounds 1–17 and 21–25 were evaluated for their α-glucosidase inhibitory activities. Compound 11 was the most active ones with an IC(50) values of 83.4 μM. These results verify the α-glucosidase inhibitory activity of M. haplocalyx (M. canadensis) and specify its active compounds for the first time. GRAPHICAL ABSTRACT: [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13659-019-0207-0) contains supplementary material, which is available to authorized users.