Pelargonium graveolens essential oil against clinical Candida and reference isolates: insights into virulence inhibition and therapeutic perspectives.

Abstract

Background: The rising incidence of Candida-associated infections and persistent antifungal resistance, driven by biofilm formation, highlight the need for alternative therapies. Essential oils offer promise as multi-targeted natural antifungals. This study evaluates the antifungal activity of Pelargonium graveolens essential oil (PGEO), obtained by hydrodistillation of aerial parts from the Edough region (Annaba, Algeria), against various Candida species and its effects on human cells.

Methods: PGEO (yield: 0.23 ± 0.04% w/w) was characterized by GC-MS. Its antifungal activity was tested against five clinical Candida isolates (C. albicans, C. kefyr, C. krusei (syn. Pichia kudriavzevii), C. lusitaniae, C. tropicalis) and reference strain C. albicans ATCC 10231. Effects on virulence enzymes (secreted aspartyl protease, phospholipase, esterase, hemolysin) were assessed via Pz/Hz indices on solid media. Anti-biofilm activity was assessed using crystal violet staining and metabolic viability assays. Cytotoxicity was evaluated in HEK-293 human embryonic kidney cells.

Results: PGEO comprised mainly citronellol (28.68%), geraniol (5.35%), isomenthone (5.44%), and linalool (3.15%). It showed broad-spectrum antifungal activity (minimum inhibitory concentrations: 0.312-2.5 mg/mL; minimum fungicidal concentration/minimum inhibitory concentration ratios: 2), including against fluconazole-resistant C. krusei. At sub-inhibitory concentrations (minimum inhibitory concentration/4 to minimum inhibitory concentration/2); PGEO inhibited enzyme secretion by 21.30 to 65.00% depending on enzyme class and species ranging from 21.30% (esterase, C. krusei) to 65.00% (hemolysin, C. albicans ATCC 10231), reducing Candida adhesion and invasion. PGEO inhibited biofilm formation (48.7-97.8%) and metabolic activity (43.2-82.1% reduction at minimum inhibitory concentration). Cytotoxicity in HEK-293 cells yielded a CC₅₀ of 3.99 ± 0.12 mg/mL, with selectivity indices of 1.59-12.79 (SI = CC₅₀/MIC).

Conclusions: The essential oil of Pelargonium graveolens exhibits potent fungicidal, antibiofilm, and multi-target antivirulence activities against clinically relevant Candida species, including fluconazole-resistant C. krusei, while maintaining acceptable cytotoxicity toward normal mammalian cells (CC₅₀ = 3.99 ± 0.12 mg/mL; SI: 1.59-12.79). Its simultaneous inhibition of growth, key virulence enzymes, and biofilm formation at sub-inhibitory concentrations positions PGEO as a promising natural candidate for topical or adjunctive treatment of biofilm-associated candidiasis, pending in vivo validation.