Abstract
Human African trypanosomiasis (HAT), known as sleeping sickness and caused by Trypanosoma brucei, is threatening low-income populations in sub-Saharan African countries with 61 million people at risk of infection. In order to discover new natural products against HAT, thirty-seven Vietnamese essential oils (EOs) were screened for their activity in vitro on Trypanosoma brucei brucei (Tbb) and cytotoxicity on mammalian cells (WI38, J774). Based on the selectivity indices (SIs), the more active and selective EOs were analyzed by gas chromatography. The anti-trypanosomal activity and cytotoxicity of some major compounds (isolated or commercial) were also determined. Our results showed for the first time the selective anti-trypanosomal effect of four EOs, extracted from three Zingiberaceae species (Curcuma longa, Curcuma zedoaria, and Zingiber officinale) and one Lauraceae species (Litsea cubeba) with IC50 values of 3.17 ± 0.72, 2.51 ± 1.08, 3.10 ± 0.08, and 2.67 ± 1.12 nL/mL respectively and SI > 10. Identified compounds accounted for more than 85% for each of them. Among the five major components of Curcuma longa EO, curlone is the most promising anti-trypanosomal candidate with an IC50 of 1.38 ± 0.45 µg/mL and SIs of 31.7 and 18.2 compared to WI38 and J774 respectively.
Highlights
Human African trypanosomiasis (HAT) or sleeping sickness is caused by two subspecies of the parasite Trypanosoma brucei, T. brucei gambiense and rhodesiense, while another subspecies, T. brucei brucei affects non-human vertebrates [1]
These nineteen essential oils (EOs) were analyzed for dose-response activity on Trypanosoma brucei brucei (Tbb) bloodstream form and on mammalian WI38 and J774 cells to calculate IC50 values and selectivity index (SI)
Three samples extracted from three Zingiberaceae species, Curcuma longa, Curcuma zedoaria, and Zingiber officinale, and one sample extracted from a Lauraceae species, Litsea cubeba, showed the most active and selective effects with IC50 values of 3.17, 2.51, 3.10, and 2.67 nL/mL respectively and SI > 10 compared to cytotoxicity (Table 1 in bold)
Summary
Human African trypanosomiasis (HAT) or sleeping sickness is caused by two subspecies of the parasite Trypanosoma brucei, T. brucei gambiense and rhodesiense, while another subspecies, T. brucei brucei affects non-human vertebrates [1]. T. brucei gambiense causes the chronic form in West and Central. Africa while T. brucei rhodesiense causes the acute form in Eastern and Southern Africa. Many efforts were made this past decade to decrease HAT incidence, this fatal disease is still endemic in 36. Remote rural areas are the most affected partly because of high poverty, higher risk of infection from the livestock reservoir (by the tsetse fly, responsible for parasite transmission, mainly living in rural areas), and lack of health care accessibility and infrastructures for current drugs. Available drugs for the treatment of HAT: pentamidine, suramine, melarsoprol, eflornithine, and nifurtimox, have shown a lot of serious side effects and limited efficacy and the increase of drug resistance [5]
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