Bioassay-guided isolation of an antimycobacterial compound from Leonurus japonicus Houtt

Abstract

Genital tuberculosis is a chronic inflammatory disease caused by Mycobacterium tuberculosis. Leonurus japonicus Houtt. (Labiatae), also known as motherwort, is used to treat gynecological and obstetrical disorders in traditional Chinese medicine. The focus of this study was to evaluate the antimycobacterial activity of L. japonicus. Resazurin Microtiter Assay (REMA) was used to evaluate antimycobacterial activity of the aerial parts of L. japonicus extract and isolated parts. Rat model of M. tuberculosis infection in uterus was used to test the anti-tuberculosis effect of the active compound in vivo. GC-MS technique was used to investigate the effect of the active compound on lipid metabolism of M. tuberculosis. The crude EtOH extract, ethyl acetate fraction (EF), and subfraction 3 (Fr 3) of L. japonicus showed antimycobacterial activity with MIC value of 2500, 640, and 320 μg/ml, respectively. Compound 1, the active compound, was isolated from subfraction 3 and identified as leonurine. The MIC of leonurine against M. tuberculosis was 80 μg/ml. The in vivo assay revealed that leonurine could significantly reduce the mycobacterial load in rat uterus in a dose-dependent manner. GC-MS analysis indicated that leonurine produced significant interventions on the lipid metabolism of M. tuberculosis. Both L. japonicus extract and leonurine have no cytotoxicity on the Vero cell proliferation at dose of 1200 μg/ml, respectively. In conclusion, L. japonicus Houtt had antimycobacterial activty and leonurine may be a promising preclinical candidate for the treatment of genital tuberculosis.