Two naphthoquinones from Rubia cordifolia

The methanol extract of Rubia cordifolia afforded two new naphthoquinones, 2-carbamoyl-3-methoxy-1,4- naphthoquinone and 2-carbamoyl-3-hydroxy-1,4-naphthoquinone, isolated along with a known naphthoquinone and naphthohydroquinone and six known anthraquinones. The structures of the new compounds were determined on the basis of spectroscopic data and direct comparisons with synthetic compounds.