Despite tremendous advances in the prevention and treatment of infectious diseases, only few antiparasitic drugs have been developed to date. Protozoan infections such as malaria, leishmaniasis, and trypanosomiasis continue to exact an enormous toll on public health worldwide, underscoring the need to discover novel antiprotozoan drugs. Recently, there has been an explosion of research into the antiprotozoan properties of quercetin, one of the most abundant flavonoids in the human diet. In this review, we tried to consolidate the current knowledge on the antiprotozoal effects of quercetin and to provide the most fruitful avenues for future research. Quercetin exerts potent antiprotozoan activity against a broad spectrum of pathogens such as Leishmania spp., Trypanosoma spp., Plasmodium spp., Cryptosporidium spp., Trichomonas spp., and Toxoplasma gondii. In addition to its immunomodulatory roles, quercetin disrupts mitochondrial function, induces apoptotic/necrotic cell death, impairs iron uptake, inhibits multiple enzymes involved in fatty acid synthesis and the glycolytic pathways, suppresses the activity of DNA topoisomerases, and downregulates the expression of various heat shock proteins in these pathogens. In vivo studies also show that quercetin is effective in reducing parasitic loads, histopathological damage, and mortality in animals. Future research should focus on designing effective drug delivery systems to increase the oral bioavailability of quercetin. Incorporating quercetin into various nanocarrier systems would be a promising approach to manage localized cutaneous infections. Nevertheless, clinical trials are needed to validate the efficacy of quercetin in treating various protozoan infections.

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槲皮素作为一种有前途的抗原虫植物化学物质：当前知识和未来研究途径

尽管在传染病的预防和治疗方面取得了巨大进步，但迄今为止仅开发出了很少的抗寄生虫药物。疟疾、利什曼病和锥虫病等原生动物感染继续对全世界的公共卫生造成巨大损失，这凸显了发现新型抗原虫药物的必要性。最近，对槲皮素（人类饮食中最丰富的黄酮类化合物之一）抗原虫特性的研究激增。在这篇综述中，我们试图巩固目前关于槲皮素抗原虫作用的知识，并为未来的研究提供最富有成效的途径。槲皮素对多种病原体具有有效的抗原虫活性，例如利什曼原虫属、锥虫属、疟原虫属、隐孢子虫属、毛滴虫属和弓形虫。除了其免疫调节作用外，槲皮素还破坏线粒体功能，诱导细胞凋亡/坏死性细胞死亡，损害铁的吸收，抑制参与脂肪酸合成和糖酵解途径的多种酶，抑制DNA拓扑异构酶的活性，并下调各种热的表达这些病原体中存在休克蛋白。体内研究还表明，槲皮素可有效减少动物体内的寄生负荷、组织病理学损伤和死亡率。未来的研究应集中于设计有效的药物输送系统，以提高槲皮素的口服生物利用度。将槲皮素纳入各种纳米载体系统将是治疗局部皮肤感染的一种有前途的方法。然而，还需要临床试验来验证槲皮素治疗各种原虫感染的功效。