Cytotoxic anthraquinones from the stems of Rubia wallichiana Decne.

From the stems of Rubia wallichiana DECNE, thirty-four structurally related compounds were isolated and identified. Three of them, namely rubiawallin-A (1), -B (2), and -C (3), constitute the first report of their occurrence from the natural source. Their structures were determined by comprehensive analyses of their 1D and 2D NMR, and electron impact (EI) mass spectral data.