Phytochemical and antioxidant activity studies on Ononis angustissima L. aerial parts: isolation of two new flavonoids.

Ononis angustissima aerial parts extract and exudate were subjected to phytochemical and biological studies. Two new natural flavonoids, (3S)-7-hydroxy-4'-methoxy-isoflavanone 3'-β-d-glucopyranoside (1) and kaempferol 3-O-β-d-glucopyranoside-7-O-(2'''-acetyl)-β-d-galactopyranoside (4), and sixteen known compounds were isolated through a bio-oriented approach. Their structural characterisation was achieved using spectroscopic analyses including 2D NMR. The phytochemical profile of the extracts was also performed, and the antioxidant activity of all compounds was tested by three different assays. To get a trend in the results and to compare the antioxidant capacity among the different methods used, the obtained data were transformed to a relative antioxidant capacity index.