Therapeutic potential of essential oils in Acanthamoeba keratitis

New therapeutic agents for amoebic keratitis are needed considering that drugs currently marketed are toxic and not effective against protozoan cystic forms. The antimicrobial action of essential oils (EOs) is already reported in the literature, which has motivated investigations of their anti-Acanthamoeba potential. Unlike synthetic drugs, plant materials have been often identified as less cytotoxic. In this review, the anti-Acanthamoeba potential of EOs was demonstrated not only based on the anti-protozoan activity as anti-inflammatory activity. Finally, in vitro cytotoxicity studies of EOs active were analyzed. EOs were able to prevent the conversion of the protozoan trophozoite to cystic form. In a study performed with Trachyspermum ammi EO, 100% of Acanthamoeba cysts were eliminated. Thymus capitatus and Limonium oleifolium EOs showed to be more active against Acanthamoeba, presenting IC50 values close to chlorhexidine and lower than amphotericin B. For these two OEs, low in vitro cytotoxicity was also found, which result in a high selectivity index (SI > 10). Therefore, safer and more effective therapies could be achieved with OEs, and in vivo assays should be urgently performed to confirm these benefits.