Biologically active natural products from Mongolian medicinal plants Scorzonera divaricata and Scorzonera pseudodivaricata

Chromatographic separation of a crude extract obtained from the aerial parts of the Mongolian medicinal plant Scorzonera divaricata yielded the two new quinic acid derivatives feruloylpodospermic acids A and B. Both compounds feature a feruloyl group and two dihydrocaffeoyl substituents. For feruloylpodospermic acid A, the dihydrocaffeic acid substituents were found esterified at positions 1 and 5 of the quinic acid moiety, while the feruloyl group was attached at position 3. For feruloylpodospermic acid B, the substituents were linked at positions 1, 3, and 4. The aerial parts of S. pseudodivaricata that are likewise used in Mongolian traditional medicine yielded two further new natural products, for which the names scorzoneric acid and scorzonerin are proposed. Scorzoneric acid is an unusual phenolic compound featuring a central tetrasubstituted phenyl ring to which a glucose unit is bound, which in turn is substituted by an esterified acyl side chain. Further substituents of the central phenyl ring system include a butan-2-one group, which is linked to a second para-substituted phenyl ring system. Scorzonerin is a matricarin-based sesquiterpene lactone that carries an esterified dihydrocoumaric acid moiety, which in turn is glycosidically bound to glucose. The structures of all new compounds were unambiguously established from NMR ( H, C, COSY, HMBC) spectroscopic and mass spectrometric data. The new quinic acid derivatives feruloylpodospermic acids A and B exhibited strong antioxidative activity when analyzed in the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay.