Piperine augments transcription inhibitory activity of rifampicin by severalfold in Mycobacterium smegmatis

A 24:1 (w/w) mixture of antibiotic rifampicin and a plant product piperine show remarkable growth-inhibitory effect on Mycobacterium smegmatis, and this inhibition is higher than that of rifampicin alone. Interestingly, piperine alone, even at higher concentration, does not inhibit the growth of mycobacteria, As RNA polymerase is the site of action of rifampicin, the enzyme was purified from M. smegmatis and the mixture of rifampicin and piperine was found to abrogate non- specific transcription catalysed by M. smegmatis RNA polymerase, Here too the effect is higher than rifampicin alone and piperine shows no effect independently. When RNA polymerase was purified from a rifampicin-resistant strain of M. smegmatis, the enzymatic activity, otherwise resistant to rifampicin, significantly decreases in the presence of piperine along with rifampicin, Modelling studies have been carried out to explain this bioenhancing behaviour of piperine.