Antiparasitic hybrids of Cinchona alkaloids and bile acids.

A series of 16 hybrids of Cinchona alkaloids and bile acids (4a-h, 5a-h) was prepared by means of a Barton-Zard decarboxylation reaction. Quinine, quinidine, cinchonine and cinchonidine were functionalized at position C-2 of the quinoline nucleus by radical attack of a norcholane substituent. The newly synthesized hybrids were evaluated in vitro for their antitrypanosomal, antileishmanial and antiplasmodial activities, along with their cytotoxicity against WI38, a normal human fibroblast cell line. Seven compounds (4d, 4f, 4h, 5b, 5d, 5f, 5h) showed promising trypanocidal activity with IC50 values in the same range as the commercial drug suramine. Moreover all the 16 hybrids showed antiplasmodial activity (IC50 ≤ 6 µg/ml), particularly those containing a nor-chenodeoxycholane moiety (4b, 4d, 4f, 4h, 5b, 5d, 5f, 5h) with IC50 values comparable to those of the natural alkaloids, and selectivity indices in the range of 5.6-15.7.

Hydrocinchonine, cinchonine, and quinidine potentiate paclitaxel-induced cytotoxicity and apoptosis via multidrug resistance reversal in MES-SA/DX5 uterine sarcoma cells.

Multidrug resistance (MDR) is one of important issues to cause the chemotherapy failure against cancers including gynecological malignancies. Despite some MDR reversal evidences of natural compounds including quinidine and cinchonine, there are no reports on MDR reversal activity of hydrocinchonine with its analogues quinidine and cinchonine especially in uterine sarcoma cells. Thus, in the current study, we comparatively investigated the potent efficacy of hydrocinchonine and its analogues quinidine and cinchonine as MDR-reversal agents for combined therapy with antitumor agent paclitaxel (TAX). Hydrocinchonine, cinchonine, and quinidine significantly increased the cytotoxicity of TAX in P-glycoprotein (gp)-positive MES-SA/DX5, but not in the P-gp-negative MES-SA cells at nontoxic concentrations by 3-(4,5-dimethylthiazol-2-yl)-2,5--diphenyltetrazolium bromide (MTT) assay. Rhodamine assay also revealed that hydrocinchonine, cinchonine, and quinidine effectively enhanced the accumulation of a P-gp substrate, rhodamine in TAX-treated MES-SA/DX5 cells compared with TAX-treated control. In addition, hydrocinchonine, cinchonine, and quinidine effectively cleaved poly (ADP-ribose) polymerase (PARP), activated caspase-3, and downregulated P-gp expression as well as increased sub-G1 apoptotic portion in TAX-treated MES-SA/DX5 cells. Taken together, hydrocinchonine exerted MDR reversal activity and synergistic apoptotic effect with TAX in MES-SA/DX5 cells almost comparable with quinidine and cinchonine as a potent MDR-reversal and combined therapy agent with TAX.

Apoptosis induced by doxorubicin and cinchonine in P388 multidrug-resistant cells.

Acquired drug resistance is a major factor in the failure of doxorubicin-based cancer chemotherapy. We determined the ability of cinchonine to reverse doxorubicin drug resistance in a doxorubicin-resistant leukaemia cell line (mouse P388/DOX). A non-cytotoxic concentration of cinchonine (10 microM) increased the sensitivity to doxorubicin of multidrug-resistant P388/DOX cells and significantly enhanced the doxorubicin-induced apoptosis and DNA fragmentation in resistant cells, but had no effect in parent cells. Time-course studies demonstrated that DNA fragmentation was present 24 h after incubation with doxorubicin and cinchonine, indicating that DNA degradation was a preceding event. In cultured cells, cinchonine increased the intracellular accumulation of doxorubicin in the resistant cells in a dose-dependent manner. Using flow cytometry to measure the inhibition of the P-glycoprotein (P-gp) dependent efflux of rhodamine 123, cinchonine was found to be considerably more effective than quinine. The results with cinchonine suggest that there may be quinine derivatives with a similar capacity to inhibit drug transport by P-gp. Additionally, the G2/M phase cell population in resistant cells is increased by doxorubicin/cinchonine treatment. Exposure of resistant cells to 1 microM doxorubicin and 10 microM cinchonine resulted in the expression of Fas (APO-1/CD95) in cells after 6 h. These studies demonstrate that the cell killing effects of doxorubicin and cinchonine in resistant cells

Cinchonine, a potent efflux inhibitor to circumvent anthracycline resistance in vivo.

Circumvention of multidrug resistance is a new field of investigation in cancer chemotherapy, and safe and potent multidrug resistance inhibitors are needed for clinical use. We investigated several analogues of quinine for their ability to increase anthracycline uptake in resistant cancer cells. Cinchonine was the most potent inhibitor of anthracycline resistance in vitro, and its activity was little altered by serum proteins. Serum from rats treated with i.v. cinchonine produced greater uptake of doxorubicin in cancer cells (DHD/K12/PROb rat colon cells and K562/ADM human leukemic cells) than did serum from quinine-treated rats (ex vivo assay). Cinchonine was more effective than quinine in reducing tumor mass and increasing the survival of rats inoculated i.p. with DHD/K12/PROb cells and treated i.p. with deoxydoxorubicin. Moreover, the acute toxicity of cinchonine in rats and mice was lower than that of other quinine-related compounds. The lower toxicity and greater potentiation of in vivo anthracycline activity produced by cinchonine are favorable characteristics for its use as an anti-multidrug resistance agent in future clinical trials.