Phytochemical analysis of Ononis arvensis L. by liquid chromatography coupled with mass spectrometry

Ononis arvensis L. can be found overall in Europe and is used to treat infections of the urinary tract and skin diseases in ethnopharmacology. Flavonoids, hydroxycinnamic acids, oxycoumarin, scopoletin and scopolin, phytosterols, lectins, and some selected isoflavonoids were identified in O. arvensis till date; however, there is a lack of the detailed investigation of the isoflavonoid profile of the plant. With the application of high-resolution tandem mass spectrometry, the fragmentation patterns of isoflavonoid derivatives found in O. arvensis roots and aerial parts were investigated and discussed. Isoflavonoid glucosides, glucoside malonates, aglycones, and beta amino acid derivatives were characterized, among which homoproline isoflavonoid glucoside esters were described for the first time. Besides the known isoflavonoid aglycones described earlier in other Ononis species, two 2-methoxy isoflavonoid derivatives were detected. The presence of licoagroside B was verified, and its structure was also corroborated by NMR experiments. Altogether, the high-resolution fragmentation pattern of 47 isoflavonoids and glycosides is presented, and their relative quantity in the roots and the aerial parts can be evaluated. Based on this information, the chemotaxonomic relation of Ononis species and the biosynthesis of their compounds could be comprehended to a greater depth.