Phytochemical and molluscicidal investigations of Fagonia arabica.

The aqueous methanolic extract of the aerial parts of Fagonia arabica L. (family Zygophyllaceae) was successively fractionated using certain organic solvents. From the ethyl acetate fraction, two flavonoid glycosides were isolated and identified as kaempferol-7-O-rhamnoside and acacetin-7-O-rhamnoside. Four triterpenoidal glycosides were isolated from the butanolic layer. Their structures were elucidated on the basis of the spectral and chemical data as 3-O-beta-D-glucopyranosyl-(1-->3)-alpha-L-arabinopyranoside oleanolic acid (1), 3-O-alpha-L-arabinopyranosyl quinovic acid 28-O-beta-D-glucopyranoside (2), 3-O-[beta-D-glucopyranosyl-(1-->2)]-beta-D-glucopyranosyl-(1-->3)-alpha-L-arabinosyl oleanolic acid (3) and 3-O-beta-D-glucopyranosyl-(1-->3)-alpha-L-arabino-pyranosyl quinovic acid 28-O-beta-D-glucopyranoside (4). The two monodesmosidic saponins 1 and 3 were found to possess strong molluscicidal activity against Biomphalaria alexandrina snails, the intermediate host of Schistosoma mansoni in Egypt (LC90 = 13.33 and 16.44 microM), whereas the other two bidesmosidic saponins 2 and 4 as well as the two flavonoid glycosides were inactive up to 50 microM.