Chemical constituents of ethyl acetate from the leaves of Rhinacanthus nasutus

Abstract

Rhinacanthus nasutus, called “Kiến cò” in Vietnam, belonged to the family of Acanthaceae. All parts of R. nasutus are used in traditional medicine to cure eczema, herpes, tuberculosis, hepatitis, diabetes, and hypertension... Phytochemical studies on its chemical constituents have led to the identification of many types of secondary metabolites, including naphthoquinones, anthraquinones, lignans, flavonoids, phenolics, triterpenoids, and sterols, which have been found to have cytotoxic, antibacterial, antifungal, and antiplatelet activities. In Vietnam, studies on the R. nasutus were very few and limited, chemical constituents and biological activity studies on this plant will help guide further applied studies and can use this plant more effectively. Dried R. nasutus leaves, collected at Lam Dong Province - Vietnam, was extracted in methanol, and the obtained extract was successively partitioned into n-hexane, ethyl acetate (EtOAc), butanol (n-BuOH). By column chromatography method together with thin layer normal-phase chromatography on the ethyl acetate extract of its leaves, seven compounds were isolated, including umbelliferone (1), skimmin (2), sinensetin (3), kaempferol (4), quercetin (5), rutin (6) and daucosterol (7). Their chemical structures were elucidated by extensive NMR spectroscopic analysis and comparison with the literature data. Among them, skimmin (2), sinensetin (3), kaempferol (4), and quercetin (5) have been obtained in this plant for the first time.