Essential oils from Lippia thymoides: insights into their antifungal activity against Candida species from oral lesions of HIV+ individuals

Candidosis is the most common oral infection in HIV-positive individuals and appears as a result the decline of the immune system, representing a marker of disease progression. However, its treatment becomes a challenge due to the resistance to antifungal agents of some strains, particularly of non-albicans species. This highlights the needs of alternative therapeutics strategies, including herbal medicine. Thus, this study evaluated the antifungal activity of Lippia thymoides essential oils, collected in the cities of Feira de Santana and Palmeiras, Bahia, Brazil, in C. albicans and C. glabrata strains isolated from oral lesions of HIV-infected individuals. Nine Candida isolates were obtained and identified through biochemical tests. The essential oils were analyzed with respect to the phytochemical aspects by gas chromatography and mass spectrometry. The minimum inhibitory concentration test was used to assess the antifungal activity and the cytotoxicity was tested in peripheral blood mononuclear cells (PBMC), using 3-(4,5-di methyl thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The essential oil extracted from Lippia thymoides collected in Feira de Santana showed a yield of 2.80±0.80%, whereas the essential oil from specimens collected in Palmeiras presented a higher yield of 4.20±1.71%. The essential oil from Feira de Santana was characterized by a high content of sesquiterpenes, with E-caryophyllene as the main constituent (27.25±1.96%). In the essencial oil from Palmeiras, monoterpenes were predominant and the major metabolite was 1.8-cineole (30.35±2.17%), indicating that it is a new chemotype. The results revealed that the essential oils of L. thymoides are non-cytotoxic, maintaining cell viability at or above 90% across all tested concentrations. The oil from Palmeiras induced proliferation of PBMCs by 65% and 51% at concentrations of 10% and 0.125% respectively, and 2% and 16% proliferation, at concentrations of 1% and 0.25%, respectively. The oil from Feira de Santana induced PBMC proliferation at all concentrations tested. Both oils showed antifungal activity against the different Candida species at the 10%, suggesting their potential as adjunct in the treatment of oral candidiasis. Key Points: Essential oils from both chemotypes of Lippia thymoides are not cytotoxic; Essential oils of L. thymoides show antifungal activity in wild species of Candida albicans and Candida glabrata; We found a new chemotype of Lippia thymoides in Chapada Diamantina.