(R)-(+)-limonene: a promising antifungal agent against Candida glabrata

Fungal infections of the genus Candida are among the most common in the world and, consequently, resistance to existing antifungal agents is a very challenging reality. In this sense, medicinal plant-based substances can aid in the design of pharmacologically important products and contribute to the development of innovative therapeutic alternatives. Given this, the objective of this study was to investigate the antifungal potential of the monoterpene (R)-(+)-limonene against strains of Candida glabrata (Nakaseomyces glabrata). Antifungal activity was determined by the broth microdilution technique for the minimum inhibitory concentration (MIC) and, subsequently, the minimum fungicidal concentration (MFC) was determined. The mechanism of action of the possible antifungal activity was analyzed by sorbitol and ergosterol assays. Molecular docking was also performed to evaluate the molecular interactions of (R)-(+)-Limonene with the enzyme 1,3-β-glucanase and sterol 14α-demethylase. Based on the tests, (R)-(+)-Limonene presented a MIC and MFC of 256 μg/mL, with fungicidal characteristics, showing strong inhibitory activity for strains ATCC 9003, LM 13, and LM 16 and moderate activity for LM 46. The mechanism of action involves both the cell wall and the fungal plasma membrane. In addition, the molecular docking study pointed to an interaction between (R)-(+)-Limonene and the active sites of the proteins 1,3-β-glucanase and sterol 14α-demethylase (CYP51), the latter being more robust. As for the association test, the antifungal potential of (R)-(+)-Limonene was demonstrated when used individually, without association with fluconazole. Based on these findings, it can be concluded that (R)-(+)-Limonene is a very promising monoterpene for the development of new drugs for the treatment of candidiasis caused by Candida glabrata (Nakaseomyces glabrata).