In vitro effect of essential oils and isolated mono- and sesquiterpenes onLeishmania major and Trypanosoma brucei

The effect of different essential oils as well as of isolated mono- and ses quiterpenes on the viability of bloodstream forms of Trypanosoma brucei, pr omastigotes of Leishmania major and human HL-60 cells was evaluated using t he Almar Blue assay. Of the 12 essential oils and 8 terpenes investigated, only three essential oils, Melissa officinalis (balmmint) oil, Thymus vulga ris (thyme) oil, and Melaleuca alternifolia (tea tree) oil were about 50-fo ld and 80-fold more toxic to bloodstream forms of T. brucei than to HL-60 c ells, respectively. Terpinen-4-ol, the main compound of the Australian tea tree oil, was even 1000-fold more toxic to trypanosomes than to the human c ells. On the other hand, none of the essential oils and terpenes tested wer e more toxic to promastigotes of L. major than to HL-60 cells.