Isolation and characterization of free radical scavenging flavonoid glycosides from the flowers of Spartium junceum by activity-guided fractionation

Spartium junceum L. (Fabaceae) flowers are used for the treatment of peptic ulcers in Turkish folk medicine. The possible superoxide dismutase-like ac tivity of the extracts, fractions and constituents obtained through activit y-guided fractionation were studied by using in vitro electron spin resonan ce spectrometry, in order to explain the role of antioxidant principles in the potent antiulcerogenic activity of the extract. Despite the fact that t he triterpene, spartitrioside, which was previously reported as the active antiulcerogenic constituent of the flowers was found almost inactive, the f lavonoid-rich fractions showed potent antioxidant activity. Five flavonoid glycosides bearing catechol structure in ring B were isolated from the buta nol extract and their structures were elucidated using H-1- and C-13-NMR te chniques as isoquercitrin (quercetin 3 beta -glucoside) (1,); luteolin 4'be ta -glucoside (2); quercetin 3, 4'-diglucoside (3); azaleatin 3 beta -gluco side (quercetin 5-methylether 3 beta -glucoside) (4), quercetin 4'beta -glu coside (5). Flavonoids (2) and (4) showed the highest in vitro antioxidant activity with 22.59 and 19.08 U/ml, respectively. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.