α-Glucosidase inhibitors and antioxidants from root bark of Morus alba

Objective: To study the chemical constituents from root bark of Morus alba and their alpha-glucosidase inhibition and DPPH radical scavenging activities. Methods: The chemical constituents were isolated and purified by repeated column chromatographies on silica gel, Sephadex LH-20, and preparative HPLC. Their structures were elucidated by 1D and 2D NMR spectra and HR-ESI-MS. Results: Thirteen compounds 1-13 were isolated and identified. The bioactive assays revealed that compounds 1, 3 and 8 displayed strong alpha-glucosidase inhibitory activity with IC50 values of (147.1 +/- 1.1), (314.1 +/- 0.8), and (207.6 +/- 0.1) mu mol/L, respectively, which were stronger than the positive control of acarbose (418.6 +/- 0.1 mu mol/L). Compounds 10 and 11 displayed potent DPPH scavenging activity with EC50 values of (2.9 +/- 0.1) and (5.0 +/- 0.1) mu mol/L [EC50 of positive control Vitamin C was (54.8 +0.1) mu mol/L], respectively. Conclusion: To the best of our knowledge, this is the first report about the compounds 1, 3, and 8 of M. alba with alpha-glucosidase inhibitory effects. (C) 2018 Published by Elsevier B.V. on behalf of Tianjin Press of Chinese Herbal Medicines.