Aurantio‐obtusin, an anthraquinone from cassiae semen, ameliorates lung inflammatory responses

The purpose of the present study is to find the natural compound(s) having a therapeutic potential to treat lung inflammatory disorders. In our screening procedure, the methanol extract of the seeds of Cassia obtusifolia (cassiae semen) inhibited inducible nitric oxide synthase‐catalyzed nitric oxide production in alveolar macrophages (MH‐S). From the extract, 8 major anthraquinone derivatives were successfully isolated. They are chrysophanol, physcion, 2‐hydroxy‐emodin 1‐methyl ether, obtusifolin, obtusin, aurantio‐obtusin, chryso‐obtusin, and gluco‐obtusifolin, among which aurantio‐obtusin (IC50 = 71.7 μM) showed significant inhibitory action on nitric oxide production from lipopolysaccharide‐treated MH‐S cells, mainly by downregulation of inducible nitric oxide synthase expression. This down‐regulatory action of aurantio‐obtusin was mediated at least in part via interrupting c‐Jun N‐terminal kinase/IκB kinase/nuclear transcription factor‐κB pathways. Aurantio‐obtusin also inhibited IL‐6 production in IL‐1β‐treated lung epithelial cells, A549. Importantly, this compound (10 and 100 mg/kg) by oral administration attenuated lung inflammatory responses in a mouse model of lipopolysaccharide‐induced acute lung injury. Therefore, it is for the first time found that aurantio‐obtusin may have a therapeutic potential for treating lung inflammatory diseases.