Most recently the mechanism of action of piperine has been found by Indian Institute of Science, Bangalore using Mycobacterium smegmatis as the test organism [25]. An interesting observation is found that piper alone even at high concentrations does not inhibit the growth of mycobacteria. But it shows remarkable growth inhibitory effect on the microorganism and this inhibition is higher than that of refampicin alone. As RNA polymerase is the site of action of rifampicin and piperine was found to abrogate non specific transcription catalysed by M. smegmatis RNA polymerase. When RNA polymerase was purified from a rifampicinresistant strains of M. smegmatis the enzymatic activity, otherwise resistant to rifampicin, significantly decreased in presence of piperine along with Rifampicin.Enhancement of in-vivo drug bioavailability is due to inhibition of hepatic and non hepatic drug metabolizing enzymes [27]. Glucoronyl transferase activity is known to be inhibited by lowering of the endogenous UDP glucoronic acid contents and decreased transferase activity.Methylenedioxyphenyl ring in piperine is also found to be responsible for inhibition of drug metabolizing enzymes and piperine mediated inhibition of aryl hydrocarbon hydroxylase results in suppression of the procarcinogen due to direct interaction of piperine with CYP1A1[28].Bioavailability enhancing activity of drugs is also found to be partly due to the increase in the blood supply to the intrinsic vessels as a result of local vasodilation [24].One more mechanism of action of piperine was explained by Regional Research Laboratory, Jammu. Piperine is act as a modulator of cell membrane dynamics and helps in transporting the drugs across these barriers.Piperine has been demonstrated to increase the serum levels and lengthen the serum half lives of some nutritional substances, such as coenzyme Q10 and beta-carotene. The mechanism of this action is unknown. It is speculated that piperine may act as a so-called thermonutrient and increase the absorption of certain nutritional substances from the gastrointestinal tract by producing a local thermogenic action. The mechanism of enhancing the drug bioavailability may be explained by following possible explanations: a) Increased blood supply to the gastrointestinal tract, b) Increased enzymatic activities like gamma- glutamyl transpeptidase which participates in active transport of nutrients across the intestinal cells c) Non-specific mechanisms inhibiting enzymes involving in biotransformation of drugs, preventing their inactivation and elimination [29-30]
đang được dịch, vui lòng đợi..