Atividade anti-Cryptococcus neoformans do óleo essencial de Croton blanchetianus Baill

Abstract

Cryptococcosis is an opportunistic and systemic mycosis caused by Cryptococcus neoformans complex yeast species. The infection is commonly contracted by inhaling spores (basidiospores) from the environment and more rarely through inoculation into the skin. After inhaling the spores, the infection affects the lungs and may evolve to cross the blood-brain barrier, affecting the central nervous system and then leading to cryptococcal meningitis. Treatment is challenging because of the toxicity of conventional antifungal drugs used in clinical practice, in addition to the current fungal resistance that represents a significant limitation to antifungal therapy. Thus, there has been a growing interest in exploring alternative treatments for fungal infections, including the investigation of phytopharmaceuticals. The Caatinga biome hosts numerous species of medicinal plants, including the Croton blanchetianus Baill, popularly known as "quince tree". In this context, the present study aimed to investigate the antifungal potential of the essential oil (EO) extracted from C. blanchetianus in comparison to C. neoformans complex samples, considering its previously reported antimicrobial activity. Standardized techniques recommended by CLSI were employed to determine the Minimum Inhibitory Concentration (MIC) through broth microdilution and the Minimum Fungicidal Concentration (MFC) using solid media. Sixteen C. neoformans samples were tested, including 11 isolated samples from different clinical sites and 5 reference strains. The EO of C. blanchetianus demonstrated antifungal activity in 100% of the tested strains, with MIC values ranging from 6.25 mg/mL to 0.39 mg/mL, in addition, the MIC for Amphotericin B was also determined as a control for the susceptibility of the strains to the antifungal agent. Additionally, MFC of the oil indicated fungicidal activity varying from 12.5 mg/mL to 0.39 mg/mL. The antifungal activity of this EO supports findings from previous research, which also reported the antimicrobial properties, particularly against Cryptococcus. The bioactivity of C. blanchetianus EO is likely associated with its phytochemical constituents, especially spathulenol and eucalyptol, compounds also present in other Croton species known for their antimicrobial effects. Therefore, these results encourage further investigation into the synergistic potential of combining essential oils with conventional antifungals, aiming to reduce the toxicity typically associated with standard antifungal treatments for Cryptococcosis and possibly can contribute to reducing the emergence of fungal resistance.