Cassia alata L. (Fabaceae) (1) is poisonous to livestock and fish and its various parts are reported to be useful in the indigenous system of medicines (2). The present study reports a hitherto unknown compound from its roots. The isolated compound I had the molecular formula C15H506 (elemental analysis and EI-MS). Colour reactions with NaOH and (CH3COO)2Mg indicated it to be a hydroxyquinone (3). The 1H-NMR spectrum of the derived acetate suggested the presence of a formyl group in an anthraquinone having a trisubstituted A-ring and a monosubstituted B-ring. The UV and visible absorptions suggested 1,8-dihydroxylation (3). The IR spectrum showed the presence of CO groups with absorptions at 1632, 1688, and 1702 cm' and suggested the presence of chelated and nonchelated CO groups (3). The compound 1 responded to the FeC13 colour reaction and this suggested the presence of vicinal hydroxy groups. We have observed that anthraquinones lacking vicinal hydroxy groups do not respond to this colour reaction (4, 5). When they are present, there is a response to this colour reaction (4). These observations suggested compound I to be 3-formyl-1,2,8-trihydroxy-anthraquinone (alquinone). Information in detail on the work-up procedure and copies of the original spectra are obtainable from the author of correspondence.