New α-glucosidase inhibitors with p-terphenyl skeleton from the mushroom Hydnellum concrescens

The purpose of this study is to elucidate the bioactive components responsible for the the alpha-glucosidase inhibitory activity detected in the EtOAc extract of the mushroom Hydnellum concrescens. Two new p-terphenyl derivatives, concrescenins A (1) and B (2), in along with six known compounds thelephantins L (3), I (4), J (5), K (6), dihydroauran-tiacin dibenzoate (7), and curtisian A (8) were isolated from the fruiting bodies of H. concrescens. Their chemical structures were elucidated by NMR experiments. Compounds 1-4 and 6-8 showed the inhibitory activity against alpha-glucosidase with the IC50 of 0.99, 3.11, 4.53, 18.77, 2.98, 5.16, and 8.34 mu M, respectively. Kinetic analysis of alpha-glucosidase indicated that compounds 1 and 2 inhibited the activity of alpha-glucosidase in a noncompetitive fashion with a Ki value of 0.02 and 021 mu M, respectively. In antioxidant evaluation, compounds 1 and 4 showed weak DPPH scavenging activity (EC50 = 82.50 and 161.75 mu M) and weak reducing ability (EC50 = 193.57 and 152.94 mu M). The current research supports the potential use of mushroom-derived p-terphenyl derivatives for the treatment of diabetes. (C) 2014 Elsevier B.V. All rights reserved.