The initial success of any adopted anti-infective strategy to malaria is followed by a descent due to the emergence of resistance to it. The search for new drugs and drug targets is a consistent demand in this disease. Eosin B, a common laboratory dye, is reported to have good antiparasitic properties in vitro. It was studied for its antiparasitic effect in vivo on chloroquine-sensitive Plasmodium berghei murine malaria. Eosin B was administered in 2 different doses by either the oral or parenteral route, once or twice daily to mice infected with Plasmodium berghei. Both the doses of eosin B 400？mg/kg and 800？mg/kg gave better results than the controls which were 40？mg/kg chloroquine and 100？mg/kg of arteether with significance. Percentage suppressive activity by Peter’s test of eosin B was better, though at a higher dose than both the controls. Survival rate of mice receiving the higher dose of eosin B was longer than that of the controls. When administered twice daily, the mice were fully cured after 4 days. Eosin B seems to be a promising drug exhibiting good antimalarial effects in the murine model of the disease. 1. Introduction Malaria is the major cause of morbidity and mortality in tropical countries. In 2010, WHO reported 216 million cases of malaria with an estimated 655,000 deaths, 86% of the victims were children under 5 years of age, and 91% of the deaths occurred in Africa. It should; however, be noted that the number of disease cases has decreased for the first time in years and malaria mortality rates have fallen by more than 25% since 2000 . Different reasons can be evinced for the reemergence of malaria, it could be due to spread of resistance to the first-line antimalarial drugs; cross-resistance between members of the limited number of drug families available; in some areas, multidrug resistance. The search for new drugs is imperative as discovery of new treatments and appearance of resistance to it takes a certain period of time. In the past decade, Chinese researchers have discovered artemisinin (qinghaosu), the active component of Artemisia annua, a herbal remedy used in Chinese folk medicine for 2000 years. This molecule with its oil-soluble (e.g., artemether and arteether), water-soluble (e.g., artesunate), and semisynthetic derivatives has shown excellent anti-Plasmodium efficacy in vitro. They are being used in combination with traditional antimalarials drugs such as mefloquine , but there is a ban on artemisinin monotherapy due to recent reports of resistance to artemisinin in Plasmodium falciparum on the Cambodian
N. J. White and P. L. Olliaro, “Strategies for the prevention of antimalarial drug resistance: rationale for combination chemotherapy for malaria,” Parasitology Today, vol. 12, no. 10, pp. 399–401, 1996.
J. L. Vennerstrom, M. T. Makler, C. K. Angerhofer, and J. A. Williams, “Antimalarial dyes revisited: xanthenes, azines, oxazines and thiazines,” Antimicrobial Agents and Chemotherapy, vol. 39, no. 12, pp. 2671–2677, 1995.
G. Mandi, S. Witte, P. Meissner et al., “Safety of the combination of chloroquine and methylene blue in healthy adult men with G6PD deficiency from rural Burkina Faso,” Tropical Medicine and International Health, vol. 10, no. 1, pp. 32–38, 2005.
P. E. Meissner, G. Mandi, S. Witte et al., “Safety of the methylene blue plus chloroquine combination in the treatment of uncomplicated falciparum malaria in young children of Burkina Faso,” Malaria Journal, vol. 4, article 45, 2005.
B. Coulibaly, A. Zoungrana, F. P. Mockenhaupt et al., “Strong gametocytocidal effect of methylene blue-based combination therapy against falciparum malaria: a randomised controlled trial,” PLoS ONE, vol. 4, no. 5, article e5318, 2009.
C. E. Atreya, E. F. Johnson, J. J. Irwin et al., “A molecular docking strategy identifies eosin B as a non-active site inhibitor of protozoal bifunctional thymidylate synthase-dihydrofolate reductase,” Journal of Biological Chemistry, vol. 278, no. 16, pp. 14092–14100, 2003.
F. Sperling, “Nonlethal parameters as indices of acute toxicity: inadequacy of the acute LD50,” in New Concepts of Safety Evaluation, D. A. Dayan, Ed., p. 177, John Wiley and Sons, New York, NY, USA, 1976.
K. Arora and A. K. Srivastava, “Antimalarial efficacy of methylene blue and menadione and their effect on glutathione metabolism of Plasmodium yoelii-infected albino mice,” Parasitology Research, vol. 97, no. 6, pp. 521–526, 2005.
K. M. Massimine, M. T. McIntosh, L. T. Doan et al., “Eosin B as a novel antimalarial agent for drug-resistant Plasmodium falciparum,” Antimicrobial Agents and Chemotherapy, vol. 50, no. 9, pp. 3132–3141, 2006.