Phenolic constituents with potent α-glucosidase inhibitory and cytotoxic activities from Rumex nepalensis var. remotiflorus

Quantitative analysis of Rumex nepalensis var. remotiflorus revealed that its roots contain rich anthraquinones, which has emodin, chrysophanol, and physcion contents of up to 0.30, 0.67, and 0.98 mg/g, respectively. Further phytochemical study led to the isolation and purification of seven undescribed phenolic constituents, including one flavan derivative with a 13-membered ring, polygorumin A (1), two dianthrone glucosides, polygonumnolides F and G (2, 3), two diphenylmethanones, rumepalens A and B (4, 5), and a pair of epimeric oxanthrone C-glucosides, rumejaposides K and L (6a, 6b) from the roots of R. nepalensis var. remotiflorus. Furthermore, 1 undescribed natural product, 1-beta-D-glucoside-6 '-[(2E)-3-(4-hydroxy-3-methoxyphenyl)-2-propenoate]-3-hydroxy-5-methylphenyl (19), and 21 known phenolic compounds were obtained from the aforementioned plant for the first time. Their structures were elucidated through extensive spectroscopic data analysis. Notably, compounds 1, 4-5, and 7-9 exhibited inhibitory activity on alpha-glucosidase with IC50 values ranging from 1.61 +/- 0.17 to 32.41 +/- 0.87 mu M. In addition, the isolated dianthrone, chrysophanol bianthrone (14), showed obvious cytotoxicity against four human cancer cell lines (HL-60, SMMC-7721, A-549, and MDA-MB-231) with IC50 values ranging from 3.81 +/- 0.17 to 35.15 +/- 2.24 mu M. In silico target prediction and molecular docking studies demonstrated that the mechanism of the anticancer activity of 14 may be related to the interaction with protein kinase CK2.