Flavoalkaloids and Flavonoids from Astragalus monspessulanus

A new flavonol tetraglycoside, quercetin-3-O-[alpha-l-rhamnopyranosyl-(1 -> 2)-[alpha-L-rhamnopyranosyl-(1 -> 6)]-beta-D-galactopyranosyl]-7-O-beta-D-glucopyranoside (1), and two new flavonol alkaloids, N-(8-methylquercetin-3-O-[alpha-L-rhamnopyranosyl-(1 -> 2)-[alpha-L-rhamnopyranosyl-(1 -> 6)]-beta-D-galactopyranosyl])-3-hydroxypiperidin-2-one (2) and N-(8-methylkaempferol-3-O-[alpha-L-rhamnopyranosyl-(1 -> 2)-[?-l-rhamnopyranosyl-(1 -> 6)]-beta-D-galactopyranosyl])-3-hydroxypiperidin-2-one (3), were isolated from the aerial parts of Astragalus monspessulanus ssp. monspessulanus. Two rare flavonoids with an unusual 3-hydroxy-3-methylglutaric acid moiety, quercetin-3-O-alpha-L-rhamnopyranosyl-(1 -> 2)-[6-O-(3-hydroxy-3-methylglutaryl)-beta-D-galactopyranoside (4) and kaempferol-3-O-alpha-L-rhamnopyranosyl-(1 -> 2)-[6-O-(3-hydroxy-3-methylglutaryl)-beta-d-galactopyranoside (5), were isolated from the aerial parts of A. monspessulanus ssp. illyricus. In addition, the eight known flavonoids alangiflavoside (6), alcesefoliside (7), mauritianin (8), quercetin-3-beta-robinobioside (9), cosmosine (10), apigenin-4'-O-glucoside (11), trifolin (12), and rutin (13) were isolated from aerial parts of A. monspessulanus ssp. monspessulanus. Their structures were elucidated via NMR and HRESIMS data. In a model that tested t-BuOOH-induced oxidative stress on isolated rat hepatocytes, flavonoids 1-13 had statistically significant cytoprotective activity similar to that of silymarin, tested at 60 mu g/mL. The most prominent effects were observed for flavonoids 1, 4, 7, and 12.