Anthraquinones and naphthohydroquinones from Rubia cordifolia

Four naphthohydroquinones and their glycosides, and 11 anthraquinones and their glycosides were isolated from the dried roots of Rubia cordifolia var. pratensis. Six of them, dihydromollugin, 2-carbomethoxy-3-(3′- hydroxy)isopentyl-1,4-naphthohydroquinone 4-O-β-glucoside, 2-methyl-1,3,6-trihydroxy-9,10-anthraquinone 3-O-β-glucoside, 2-methyl-1,3,6-trihydroxy-9,10-anthraquinone 3-O-(3′-O-acetyl)-α-rhamnosyl (1→2)-β-glucoside, 2-methyl- 1,3,6-trihydroxy-9,10-anthraquinone 3-O-(3′,6′-O-diacetyl)-α-rhamnosyl(1→2)-β-glucoside and 2-methyl-1,3,6-tri- hydroxy-9,10-anthraquinone 3-O-(4′,6′-O-diacetyl)-α-rhamnosyl(1→2)-β-glucoside, were isolated for the first time from a natural source. The structures were established by various chemical and spectroscopic methods. The chemotaxonomic significance of these findings is discussed briefly.