Chemical Constituents and Biological Activities of Strobilanthes crispus L.

Phytochemical investigation of Strobilanthes crispus has led to the isolation of 1-heptacosanol (1), tetracosanoic acid (2), stigmasterol (3) from the hexane extract, a mixture of four C-20-C-24 fatty acid esters of beta-amyrin (4), taraxerol (5), taraxerone (6), a mixture of two C-22 and C-24 fatty acid esters of taraxerol (7) from the dichloromethane extract, 4-acetyl-2,7-dihydroxy-1,4,8-triphenyloctane-3,5-dione (8) and stigmasterol beta-D-glucopyranoside (9) from the methanol extract. The dichloromethane and methanol crude extracts together with the isolated compounds (4-9) were tested for antibacterial activity using the determination of minimum inhibitory concentration assay and acetylcholinesterase inhibitory activity using the micro-plate assay. The majority of the samples tested indicated good activity against the Gram-positive bacteria (7.8-125.0 mu g/mL), and moderate to weak activity against the Gram-negative bacteria (31.0-250.0 mu g/mL) employed. Moderate to weak activity was observed against acetylcholinesterase. Compound (8) showed excellent antibacterial activity against Bacillus subtilis and Staphylococcus aureus, with MIC values of 15.6 and 7.8 mu g/mL, respectively, and significant activity against Escherichia coli and Salmonella typhimurium, with MIC values of 62.5 and 31.0 mu g/mL, respectively. Compound (8) also showed the highest acetylcholinesterase inhibitory activity, with an IC50 value of 31.0 mu g/mL. This is the first report describing the antibacterial and acetylcholinesterase inhibitory activities of S. crispus on the basis of the isolated constituents. This research work has provided scientific proof of the traditional medicinal use of the leaves of S. crispus.