Three lignans and one coumarinolignoid with quinone reductase activity from Eurycorymbus cavaleriei

Four compounds, including one new lignan cavaol H (1), one new coumarinolignoid 5′-hydroxycleomiscosin B (4) and two known lignans (2-3) were isolated from the 95% ethanol extract of the twigs of Eurycorymbus cavaleriei. Their structures were established on the basis of various spectroscopic analyses including 1D-(¹H, ¹³C, and DEPT) and 2D-NMR (COSY, HMQC, and HMBC). The absolute stereochemistry of the two known lignans was firstly reported in this article by ¹H NMR studies on Mosher's ester derivatives. In the present study, quinone reductase induction activities of compounds 1-4 were assayed, compound 4 showed moderate quinone reductase induction with concentration to double the enzyme activity (CD) of 10.5 ± 0.8 μg/mL. Then we established LC-MS-MS analysis of glutathione (GSH) incubation with compound 4 to explain whether compound 4 induced quinone reductase through alkylating of the sulfhydryl groups of Keap1. Reconstructed selected ion chromatogram (SIC) of m/z 706 after compound 4 incubation with GSH was different from that with Tris-HCl buffer solution, which meant the quinone reductase induction activity of compound 4 attributed to alkylating the sulfhydryl groups of Keap1.