Phytochemical investigations of the aerial parts of the plant Cephalaria taurica Szabó. (Caprifoliaceae) have resulted in the isolation of nine oleanane-type triterpenoid saponins, of which two still remain undescribed. The structures of tauricosides A and B were characterized based on NMR analysis, HRESIMS spectrometry, and chemical evaluations. The saponins tauricosides A and B have been rarely reported in the literature due to the presence of eight sugar moieties, and this is also the first report of saponins containing eight sugar moieties in the Caprifoliaceae family. The cytotoxic activities of tauricosides A and B, their undescribed prosapogenins, aglycone hederagenin, and n-butanol extract of C. taurica against the cancerous cells A-549, HeLa, PANC-1, and SH-SY5Y and the noncancerous HEK-293 cells were evaluated by the MTT method. Although tauricosides A and B and the crude n-butanol extract did not exhibit any activity at the tested concentrations on all the tested cells, after alkaline hydrolysis, the cytotoxic activity potential of the compounds was obviously improved. The most active compound, obtained after the alkaline hydrolysis of tauricoside B, showed a significant inhibitory effect, which was higher than that of the standard, commercially available drug doxorubicin, on the cancerous A-549, HeLa, PANC-1, and SH-SY5Y cells with IC50 values of 9.04, 8.75, 6.87, and 4.32 μM, respectively. In addition, prosapogenin, obtained after the alkaline hydrolysis of tauricoside A, exhibited considerable cytotoxic activity on the cancerous A-549, HeLa, PANC-1, and SH-SY5Y cells, with IC50 values of 13.19, 10.32, 11.91, and 7.49 μM, respectively. In conclusion, the alkaline hydrolysis of the saponins (tauricosides A and B) obviously improved their cytotoxic activity potential.
Keywords: Caprifoliaceae; Cephalaria taurica; Cytotoxic activity; Saponins; Tauricosides A and B.
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