Biol. Pharm. Bull. 30(11) 2207—2210 (2007)

identified hyperglycemia as the main risk-factor for the development of complications. Persistent hyperglycemia induces abnormal changes such as the formation of advanced glycation end products (AGEs), the increase of sorbitol through the polyol pathway, the overactivation of protein kinase C isoforms due to the synthesis of diacylglycerol (DAG). Direct evidence indicating the contribution of AGEs in the progression of diabetic complications in different lesions of the kidneys, the rat lens, and in atherosclerosis has been recently reported. Ne-Carboxymethyllysine (CML) is one of the best characterized compounds of AGEs and can be detected in tissue and serum proteins by specific antisera. Aldose reductase (AR), the key enzyme in the polyol pathway, also has been demonstrated to play important roles in the pathogenesis of diabetic complications and cataract formation. Thus, the design and discovery of inhibitors of AGEs formation or AR can offer a promising therapeutic approach for the prevention of diabetic or other pathogenic complications. In our ongoing project directed toward the discovery of preventive agents for diabetic complications from the herbal medicines, the seeds of Cassia tora was chosen for more detailed investigation, since the EtOAc-soluble fraction of a MeOH extract showed a significant in vitro inhibitory effect on AGEs. Cassia tora (Leguminosae) is widely distributed in tropical Asian countries. The seeds of C. tora are reputed in Oriental medicine as vision-improving, antiasthenic, asperient, and diuretic agents. C. tora have shown to possess various biological and pharmacological activities including antihepatotoxic, radical scavenging, antiallergic, antimutagenic, antifungal, and antimicrobial. Previous phytochemical investigation on the seeds of C. tora have resulted in the isolation of several anthraquinone and naphthopyrone derivatives. In the present study, further fractionation of the EtOAc-soluble extract of the seeds of C. tora led to the purification of nine anthraquinones (1—9). The structures of 1—9 were determined by spectroscopic data interpretation and they were subjected to in vitro bioassays to evaluate their inhibitory activity against AGEs and RLAR.