Study of chemical composition and antimicrobial activity of leaves and roots of Scrophularia ningpoensis

Two saponins: scrokoelziside A (1), scrokoelziside B (2), one iridoid glycoside, eurostoside (3), and two flavonoids: nepitrin (4) and homoplantaginin (5), were isolated from the leaves of Scrophularia ningpoensis for the first time. Moreover, eight known compounds: cane sugar (6), harpagide (7), aucubin (8), 6-O-methylcatalpol (9), harpagoside (10), angoroside C (11), -sitosterol (12) and -sitosterol glucoside (13) were isolated from the roots of S. ningpoensis. Furthermore, the antimicrobial activity of the extracts of the leaves of S. ningpoensis and the 10 compounds (1, 2, 3, 4, 5, 7, 8, 9, 10, 11) was studied in vitro against eight reference strains of bacteria by using the disc-diffusion method and micro-well dilution assay. The extracts of leaves and scrokoelziside A are effective against beta-haemolytic streptococci but had no effect against other strains. The extract of roots and other compounds showed no activity against all bacterial strains at the test concentration.