Cinchonin

The inhibitory effect of cinchonine on human platelet aggregation due to blockade of calcium influx.[Pubmed: 9776305]

Biochem Pharmacol. 1998 Oct 15;56(8):955-60.

The Cinchona bark contains alkaloids like quinine, quinidine, Cinchonine and cinchonidine. These agents are effective antimalarial drugs and have been used clinically in malaria caused by Plasmodium falciparum. Previous studies show that quinine and quinidine exert effects on cardiovascular system.
METHODS AND RESULTS:
This study was conducted to examine the effect of Cinchonine on human platelet aggregation. The results show that Cinchonine inhibited platelet aggregation mediated by platelet agonists, epinephrine (200 microM), ADP (4.3 microM), platelet activating factor (PAF; 800 nM) and collagen (638 nM) but had no effect on arachidonic acid (AA; 0.75 mM). Cinchonine was most effective in inhibiting aggregation induced by platelet activating factor and epinephrine with IC50 values of 125 and 180 microM respectively, however, higher concentrations of Cinchonine were required to inhibit aggregation mediated by ADP or collagen (IC50; 300 microM). Pretreatment of platelets with Cinchonine inhibited aggregation caused by Ca2+ ionophore, A-23187 (6 microM), in a dose-dependent manner (IC50; 300 microM) indicating an inhibitory effect on Ca2+-signaling cascade. This was supported by measuring [Ca2+]i in platelets loaded with Fura-2AM where Cinchonine inhibited the rise in cytosolic Ca2+ mediated by A-23187 (6 microM) or collagen (638 nM). Results show that Cinchonine (20 microM) also inhibited aggregation when platelets were pretreated with protein kinase C (PKC) activator, phorbol myristate acetate (PMA; 0.1 microM) in combination with low doses of platelet activating factor (80 nM). Cinchonine, however, had no effect on AA-induced platelet aggregation and thromboxane A2 (TXA2) synthesis in platelets.
CONCLUSIONS:
These results suggest that antiplatelet effects of Cinchonine are mediated mainly through inhibition of Ca2+-influx and protein kinase C pathways in platelets.

Cinchonine Prevents High-Fat-Diet-Induced Obesity through Downregulation of Adipogenesis and Adipose Inflammation.[Pubmed: 22675336]

PPAR Res. 2012;2012:541204.

Cinchonine (C(19)H(22)N(2)O) is a natural compound of Cinchona bark. Although Cinchonine's antiplatelet effect has been reported in the previous study, antiobesity effect of Cinchonine has never been studied.
METHODS AND RESULTS:
The main objective of this study was to investigate whether Cinchonine reduces high-fat-diet- (HFD-) induced adipogenesis and inflammation in the epididymal fat tissues of mice and to explore the underlying mechanisms involved in these reductions. HFD-fed mice treated with 0.05% dietary Cinchonine for 10 weeks had reduced body weight gain (-38%), visceral fat-pad weights (-26%), and plasma levels of triglyceride, free fatty acids, total cholesterol, and glucose compared with mice fed with the HFD. Moreover, Cinchonine significantly reversed HFD-induced downregulations of WNT10b and galanin-mediated signaling molecules and key adipogenic genes in the epididymal adipose tissues of mice. Cinchonine also attenuated the HFD-induced upregulation of proinflammatory cytokines by inhibiting toll-like-receptor-2- (TLR2-) and TLR4-mediated signaling cascades in the adipose tissue of mice.
CONCLUSIONS:

Our findings suggest that dietary Cinchonine with its effects on adipogenesis and inflammation may have a potential benefit in preventing obesity.

Cinchonine, a potent efflux inhibitor to circumvent anthracycline resistance in vivo.[Pubmed: 1581892]

Cancer Res. 1992 May 15;52(10):2797-801.

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.
METHODS AND RESULTS:
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.
CONCLUSIONS:
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.

Hydrocinchonine, cinchonine, and quinidine potentiate paclitaxel-induced cytotoxicity and apoptosis via multidrug resistance reversal in MES-SA/DX5 uterine sarcoma cells.[Pubmed: 20196146]

Environ Toxicol. 2011 Aug;26(4):424-31.

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.
METHODS AND RESULTS:
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.
CONCLUSIONS:
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.