Structural determination and in vitro tumor cytotoxicity evaluation of five new cycloartane glycosides from Asplenium ruprechtii Sa. Kurata

Five new cycloartane glycosides, named aspleniumside A - E, were discovered and characterized by re-investigated the remaining extracts of the whole plant of Asplenium ruprechtii Sa. Kurata, a famous folk medicine for treating thromboangitis obliterans in China, Japan, and Korea. Compounds 3-5 possessed the 9,19-seco-cycloartane-9,11-en triterpene aglycone with 3,7(or 23),24,25,30-highly oxidized methylene, methylene or quaternary carbons, that was found in this species for the first time. The stereo-chemistry of all new compounds were fully discussed by extensive analysis of the 1D and 2D NMR data, and comparisons with those data of known compounds. 24R configuration was determined here which indicated the different growing areas of the same species could influence the secondary metabolic behavior, leading to the differences in chemical composition. All glycoside groups were determined as β-d-glucopyranosyl by ¹H coupling constant of anomeric protons and co-TLC of the acid hydrolysate with d-glucose. All the cycloartane glycosides were evaluated against HL-60 and HepG2 cells for cytotoxicity, compounds 1-3, showed potential cytotoxicity with the IC₅₀ in range of 18-60 μM, while the standard sorafenib showed IC₅₀ value of 10.61 ± 0.43 and 13.43 ± 1.12 μM against HL-60 and HepG2, respectively. The results attained in this study indicated that cycloartane glycosides should be the cytotoxicity substance in A. ruprechtii Sa. Kurata, and had the potential to be developed as tumor cytotoxicity agent applied in clinic.

Keywords: Asplenium ruprechtii; Cycloartane glycoside; Cytotoxicity; Structural determination.