Evaluation of the anti-Candida albicans activity of the main monoterpenes of the essential oil of Cymbopogon nardus (L.) Rendle

Abstract

In recent years the number of infections caused by opportunistic microorganisms has increased and Candida genus is relevant because its pathogenicity. Candida colonizes the human microbiota into gastrointestinal tract and oral and vaginal mucosa. Besides Candida is a cause of nosocomial infections. Candida species can cause vulvovaginal candidiasis (CVV), which is the most common form of opportunistic fungal infection. The treatment of vulvovaginal candidiasis and other infections caused by Candida, involves the derivatives of azole compounds (fluconazole) and polyene compounds (amphotericin-B). However, these drugs have limitations because of the eukaryotic nature of fungal cells that resemble host cells, so these drugs exhibit toxicity, narrow spectrum of activity, and poor efficacy. In addition, inadequate exposure to conventional antifungals leads to the predominance of resistant strains, which express genes that allow the fungus to survive. Among the factors of virulence can be mentioned: biofilm formation, morphological transition between yeast and hyphae, adhesion to host cells or surfaces of biotic and abiotic materials and production of hydrolytic enzymes, such as proteases, phospholipases and hemolysins. Cymbopogon nardus (L.) Rendle (citronella) belongs to grasses (Poaceae) and its essential oil is frequently used in perfumery, cosmetics and as insect repellent due to its main metabolites such as geraniol, citral, citronellal and citronellol. Studies have shown the activity of this plant as antifungal, antibacterial, antiviral, and antioxidant. A recent study performed by our research group demonstrated the in vitro antifungal activity of the essential oil from C. nardus (OE) leaves against the standard and clinical strains of Candida species. This study showed expressive action of OE against the main factors of virulence, such as, formation of hyphae and mature biofilms of C. albicans. In addition, our group performed chemical analysis of essential oil, reporting as major oxygenated monoterpenes: citronellal (27.87%), geraniol (22.77%), geranial (14.54%), citronellol, 85%) and neral (11.21%). These results are promising and encouraged the development of the present study, which aims to evaluate the activity of the components of OE, such as, citronellal, geraniol, citronellol and citral (geranial and neral) on planktonic cells and mature biofilm of C. albicans against standard and clinical strain, in order to correlate the antifungal activity of OE with its main chemical components. In addition, we emphasize that this study will evaluate the combination of the chemical components with the main conventional antifungals. The antifungal activity will be evaluated by minimum inhibitory concentration and minimum fungicidal concentration, with spectrophotometric readings, and 2,3,5-triphenyltetrazolium chloride (TTC), antibiofilm potential and checkerboard. (AU)