Antileishmanial activity of quinovic acid glycosides and cadambine acid isolated from Nauclea diderrichii.

Nine quinovic acid glycosides and the alkaloid cadambine acid isolated from N. diderrichii, an evergreen endemic plant of West and Central Africa, were assessed for their in vitro antileishmanial activity against Leishmania infantum. Four quinovic acid glycosides and cadambine acid revealed a strong antileishmanial activity (IC (50) = 1 microM) highly specific for the intracellular amastigote form of the parasite. Quinovic acid glycosides were shown to inhibit parasite internalisation by interfering with promastigotes while cadambine acid exerted immunomodulatory activity by inducing NO production in human macrophages. The association of cadambine acid with amphotericin B demonstrated an interesting synergism, suggesting that cadambine acid could be used as a complement of such conventional therapy.