Chemical composition and evaluation of the anti-Candida activity of essential oils of Croton jacobinensis Baill. and its main compound α-pinene: in vitro and in vivo insights

Abstract

Ethnopharmacological relevance: Commonly known as "marmeleiro", Croton jacobinensis Baill. (syn. Croton sonderianus) is a plant native and endemic to Brazil. In traditional medicine, preparations made from the bark of this species are used to treat inflammation, skin infections, wound healing, and gastrointestinal disorders.

Aim of the study: The present study aimed to investigate the chemical composition and evaluate the in vitro and in vivo anti-Candida activity of the essential oils from the leaves (EOL), bark (EOB), and inflorescences (EOI) of C. jacobinensis and its major compound α-pinene, as well as to investigate the possible mechanisms of action involved.

Materials and methods: The chemical composition of EOL, EOB, and EOI was determined by gas chromatography coupled with mass spectrometry (GC-MS). The in vitro antifungal activity of C. jacobinensis essential oils against Candida albicans, Candida glabrata, Candida krusei, and Candida parapsilosis was evaluated using the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) methods. The mechanisms of action related to ergosterol synthesis and osmotic protection by sorbitol were also investigated. To confirm the antifungal potential in vitro, assays were performed using an experimental model of Candida infection in Tenebrio molitor larvae.

Results: The yields of essential oils were 2.00, 1.87, and 0.62% for the inflorescence, stem bark, and leaves, respectively. Regarding the chemical analysis by GC-MS, 31 compounds were identified in EOI, 29 in EOL, and 22 in EOB. The monoterpene α-pinene was identified as one of the major compounds in OEB (68.07%), EOI (16.78%), and EOL (10.12%). The MIC and MFC for EOL, EOB, EOI, and α-pinene ranged from 64 to 256 μg/mL against all Candida strains evaluated. Interestingly, EOB showed the best results against C. albicans (MIC and MFC = 64 μg/mL), while α-pinene exhibited higher MIC (128 μg/mL) and MFC (256 μg/mL) values against this strain. It was observed that the presence of ergosterol and sorbitol negatively affected the IC₅₀ of essential oils and α-pinene against all Candida strains. The in vivo study confirmed the antifungal effects of essential oils and α-pinene, where T. molitor larvae infected with fungal inoculum and treated with these products showed increased survival time.

Conclusions: The essential oils of C. jacobinensis showed antifungal potential, probably due to the disruption of membrane permeability and the rupture of the fungal cell wall. When evaluated in isolation, the major compound α-pinene did not overcome the effects of the essential oils of C. jacobinensis against Candida strains in in vitro and in vivo models. These findings suggest that other components of the oils, besides α-pinene, may act synergistically against fungal pathogens. The essential oils of C. jacobinensis corroborate the traditional use of this plant in the treatment of skin infections.

Keywords: Antifungal; Ergosterol; Monoterpenes; Sorbitol; Volatile oil.