Evaluation of Antiplasmodial Activity and Safety of Flower Extracts of Chrysanthemum cinerariaefolium, Singly and in Combination with Chloroquine, Lumefantrine and Piperaquine

Objective: To evaluate the antiplasmodial activity and safety of organic and aqueous flower extracts of Chrysanthemum cinerariaefolium from Kenya, singly and in combination with chloroquine, lumefantrine and piperaquine. Methodology: Antiplasmodial activity of organic and aqueous flower extracts of C. cinerariaefolium was assessed in vitro by serial micro-dilution assay technique against Plasmodium falciparum, and in vivo using the 4-day suppressive test as well as the established infection test against P. berghei ANKA in mice. To determine the safety of the extracts, cytotoxicity evaluation of extracts against Vero E6 cells and acute toxicity studies in mice were also done. Results: In vitro antiplasmodial assays showed that methanolic extract of C. cinerariaefolium flowers was active, petroleum ether extract was moderately active, while the aqueous extract was inactive. Methanolic extract combined with chloroquine (CQ) against CQ-sensitive (3D7) and CQ-resistant (W2) P. falciparum showed marked synergy. Both methanol and aqueous extracts (1000mg/kg) showed chemosuppression of >45% (P<0.05) in both 4-day suppression test and established infection test against P. berghei ANKA in mice. Lumefantrine (LU) or piperaquine (PQ) combined with either methanol or aqueous extracts showed chemosuppression of >63% (P<0.05) against LU-resistant and PQ-resistant P. berghei ANKA strains, indicating synergistic interactions. Methanolic and aqueous flower extracts of C. cinerariaefolium had no cytotoxic effect on Vero E6 cells and no overt signs of toxicity in mice. Conclusion: The findings showed that C. cinerariaefolium flower extracts are safe in mammalian systems, have antiplasmodial activity and have potentiation effect of conventional antimalarials. There is need therefore to further explore the plant’s bioactive molecules which may serve as template for development of novel, effective and affordable antimalarial agents for management of malaria.

Possible involvement of IFN-gamma in early mortality of Plasmodium berghei NK65-infected BALB/c mice after febrifugine treatment.

Parasitemia patterns, survival and cytokine levels of Plasmodium berghei NK65-infected BALB/c mice, treated orally with the alkaloidal mixture of febrifugine and isofebrifugine at a dose of 1 mg/kg twice a day for 4 consecutive days were monitored. Whereas the untreated mice showed a progressive increase in parasitemia and ultimate death, the alkaloid mixture-treated group showed a transient suppression of parasitemia during the course of treatment. However, the parasitemia increased on discontinuation of treatment, leading to earlier death of mice in the treated group than in the infected but untreated controls. Mice in the infected but untreated group displayed a significant elevation in serum IFN-gammay levels during the first week post-infection (pI) and from Day 14 pI, relative to the levels in the uninfected controls. In contrast, although mice in the alkaloid mixture-treated group displayed no significant elevation in serum IFN-gamma levels during the first week pI, they showed considerable levels on Day 14 pI. There were no significant differences in serum IL-4 levels among the groups. The titers of the parasite-specific IgG1, IgG2a, IgG2b and IgG3 were significantly elevated from Day 11 pI in both the treated and untreated groups. There was a significant difference in survival duration between the IFN-gamma-/- mutant and BALB/c mice. IFN-gamma-/- mutant mice showed a decrease in parasitemia levels while receiving medication, which was significantly lower than those of the treated BALB/c mice. The results of the present study suggest that although IFN-gamma is significant for protective immunity in mice with malaria infection, it may play an adverse role post-medication, causing earlier mortality of treated BALB/c mice.

Chloroquine efficacy in Plasmodium berghei NK65-infected ICR mice, with reference to the influence of initial parasite load and starting day of drug administration on the outcome of treatment.

We examined whether the initial number of parasites inoculated and the starting day of medication post-infection influenced the antimalarial efficacy of chloroquine (CQ) against Plasmodium berghei NK65 infection in ICR mice. Male ICR mice were inoculated intraperitoneally with 1 x 10(5), 1x10(6), 1 x 10(7), 1 x 10(8) P. berghei NK65-parasitized erythrocytes (pRBC). In the treated group, all mice received an oral dose of 20 mg/kg of CQ base for 4 days starting on day 0 after infection. From day 3, Giemsa-stained thin blood smears from tail vein blood were used to assess parasitemia. Mice in the untreated control in each group showed a progressive increase in parasitemia leading to death. Treatment of mice, inoculated with 1 x 10(5), 1 x 10(6) and 1 x 10(7) pRBC, with CQ showed a marked effect. All the mice survived during the experiment. During the observation period, malaria parasites could not be detected on microscopic examination. Conversely, mice inoculated with 1 x 10(8) pRBC showed little response to CQ treatment, and all mice showed a progressive increase in parasitemia and ultimately died. In another experiment, mice infected with 1 x 10(3) and 1x 10(5) pRBC were treated with an oral four-day dosage of 20 mg/kg of CQ base from days 2, 3 or 4 post-infection. Treatment of mice, inoculated with 1 x 10(3) pRBC, with CQ from days 2 and 3 showed a marked effect. All mice survived during the experiment. However, treatment from day 4 showed a limited derease in parasitemia and all the mice ultimately died. On the other hand, treatment from day 2 showed a marked effect against 1 x 10(5) P. berghei NK65-infected mice, but treatment from days 3 or 4 was only slightly effective and all the mice died with an increasing parasitemia. The present results indicate that in in vivo antimalarial drug-assay systems, several factors, sush as initial parasite load and starting time of treatment may influence the drug response in the host.