Abstract

Background Tuberculosis continues to be a serious health problem, and drug-resistant tuberculosis is an increasing threat that directly impacts the tuberculosis control program. These can be prevented or controlled by combining several drugs with antituberculous activity. In the present study, an attempt is made to understand the combinatorial effect of two medicinal plant extracts i.e. Piper longum and Cressa cretica against Mycobacterium tuberculosis.Methodology 2D checkerboard assay was used to study the combinatorial effect of the crude extracts. The 2-∆∆Ct method was used to determine the changes in gene expression of selected genes rpoB, gyrA and gyrB involved in transcription and DNA replication and intrinsic resistance of Mycobacterium tuberculosis to front-line drugs.Results Determination of the effect on gene expression at the subminimum inhibitory concentration of the crude extracts. The required MIC concentration, 125 µg/ml, was inversely reduced up to 7 µg/ml for P. longum. Similarly, the required MIC concentration of 250µg/mL of C. cretica is reduced to 10µg/mL.Conclusions The relative change in gene expression for rpoB and gyrA was 2 and 4-fold, respectively, and 1-fold for gyrB. Further characterization of the downstream target genes and in vivo studies may provide the mode of action of these two anti-mycobacterial agents.

The emergence and treatment of Drug resistant Tuberculosis (DRTB) have become a global health issue. Herbal drugs promises other possible options for Tuberculosis treatment.. In the current study, anti-mycobacterial activity of Piper longum, Cressa cretica and Calotropis gigantea extracts were tested. The methanolic extract of these plants was screened against H37Rv strain using MGIT BACTEC 960 system. The extracts showed inhibitory activity against Mycobacterium tuberculosis H37Rv strain. Piper longum and Cressa cretica showed inhibition at 125µg/mL and Calotropis gigantea at 250µg/mL. However, isoniazid and Rifampicin as standard showed higher inhibitory activity against M. tuberculosis respectively at 0.05µg/mL and 0.12µg/mL when compared to the crude extract. The present study demonstrates the anti-tubercular potential of Piper longum and Cressa cretica as a new anti-mycobacterial agent. Although, the action of these compounds and their active principles require further purification and molecular characterization besides in vivo testing to evaluate their capacity as novel anti-TB agents.