Screening of Tanzanian plant extracts for their potential inhibitory effect on P-glycoprotein mediated efflux

For years, many efforts have been made to discover new drugs using plants as natural screening libraries. In this study, extracts of 43 Tanzanian medicinal plants were screened for their potential inhibitory effect on P‐gp, using the secretory transport of Cyclosporin A (CsA) in the Caco‐2 system as a measure of the functionality of P‐gp efflux. Two out of these 43 plant extracts (extracts of Annickia kummeriae and Acacia nilotica) appeared to have a modulatory effect on P‐gp related efflux carriers. In presence of the extract of Annickia kummeriae, a concentration dependent decrease on the polarity in transport of CsA was observed; the inhibitory effect of this extract on P‐gp was comparable to that of valspodar, a known P‐gp inhibiting agent. The exact nature of the active components of these botanicals remains to be identified. Copyright © 2003 John Wiley & Sons, Ltd.