Abstract

Phytochemical analysis of the ethyl acetate extract of the stem bark of Sesbania grandiflora (L.) led to the isolation of seven compounds including, a tetracyclic diterpene, kaurenoic acid (1). Other isolated compounds include two pentacyclic triterpenes β-amyrin (2) and lupeol (3), two steroidal ketones, stigmata-4,22-dien-3-one (4) and stigmast-4-en-3-one (5) stigmasterol (6) and a fatty acid, linoleic acid (7). Structures of these compounds were characterized by extensive NMR analysis and by comparing their spectral data with the published values. Among these compounds 1, 2, 3, 4 and 5 are isolated from S. grandiflora for the first time. Chemotaxonomic significance of the isolated compounds is also described herein. A comparative biological study for antioxidant, antimicrobial, thrombolytic and cytotoxic activities of the leaf and bark extracts of the plant was also conducted. Crude methanol extracts of both leaf and bark demonstrated strong antibacterial activity against Bacillus megaterium and Aspergillus niger as compared to the standards kanamycin and ketoconazole. The dichloromethane and ethyl acetate extract of both the bark and leaf showed very mild to moderate activities against the five microorganisms studied. The petroleum ether extract of the leaf showed no activity against most of the microorganisms studied. In the cytotoxic activity assay using brine shrimp and tamoxifen as a standard, the methanol extracts of the bark indicated the highest lethality as compared to the leaf extracts. Among all the extractives the ethyl acetate extracts of leaf showed moderate antioxidant activity using DPPH free radical scavenging method with butylated hydroxyl anisole and ascorbic acid as standards whereas different bark extracts showed very mild activities. The ethyl acetate and methanol extracts of the leaf exhibited significant thrombolytic activity as compared to the standard Streptokinase.

Keywords

Sesbania grandiflora, kaurenoic acid, ?-amyrin, stigmata-4,22-dien-3-one, stigmast-4-en-3-one, antioxidant, cytotoxic, thrombolytic