Emerging Phytochemicals to Treat Leishmaniasis: A Review of Experimental Studies from 2011 to 2021

Leishmaniasis is a protozoan disease caused by a parasite from the genus Leishmania. It is known as a neglected tropical disease by WHO and is the second-leading cause of death by parasites after malaria. Chemotherapy is the only effective way to control the disease, but treatment options for leishmaniasis are limited. The majority of the drugs are costly, have serious side effects and necessitate hospitalisation. The lack of an effective vaccine, in addition to the emergence of resistance to currently available drugs, has all been raised as major concerns, especially in endemic areas of developing countries. Phytochemicals might contribute to the development of novel and effective drugs for the treatment of leishmaniasis by providing selectively targeted intervention in parasites. Many phytochemicals (quinones, alkaloids, terpenes, saponins, phenolics) and their derivatives are quite active against diverse groups of pathogens, such as viruses, bacteria, fungi and parasites. To date, many phytochemicals have shown potent anti-leishmanial activity with highly selective mode of action. However, due to a lack of interaction between academician and pharma industries none of them have undergone the clinical assessment. The present review will analyse the most promising phytochemicals and their synthetic compounds, which have shown antileishmal activity in in-vitro and subsequently in animal studies from 2011 to 2021. These phytochemicals are apigenin, hydroxyflavanone, Epigallocatechin-O-3 gallate, caffeic acid, α-bisabolol, β-caryophyllene, ursolic acid, quinones, which have shown notable anti-leishmanial activities in several independent studies.