Candida albicans is associated with serious infections in immunocompromised patients. Terpenes are natural-product derivatives, widely studied as antifungal alternatives. In a previous study reported by our group, the antifungal activity of α-pinene against C. albicans was verified; α-pinene presented an MIC between 128–512 µg/mL. In this study, we evaluate time-kill, a mechanism of action using in silico and in vitro tests, anti-biofilm activity against the Candida albicans, and toxicity against human cells (HaCaT). Results from the molecular-docking simulation demonstrated that thymidylate synthase (−52 kcal mol⁻¹), and δ-14-sterol reductase (−44 kcal mol⁻¹) presented the best interactions. Our in vitro results suggest that α-pinene’s antifungal activity involves binding to ergosterol in the cellular membrane. In the time-kill assay, the antifungal activity was not time-dependent, and also inhibited biofilm formation, while rupturing up to 88% of existing biofilm. It was non-cytotoxic to human keratinocytes. Our study supports α-pinene as a candidate to treat fungal infections caused by C. albicans.

Terpenoids, also named terpenes or isoprenoids, are a family of natural products found in all living organisms. Many plants produce terpenoids as secondary metabolites, and these make up a large part of essential oils. One of most important characteristic is that the compounds are volatile, have odor and can be used in a variety of applications in different industrial segments and traditional medicine. Brazil has a rich and diverse flora that can be used as a source of research for obtaining new molecules. Within the Brazilian flora, it is worth mentioning the Caatinga as an exclusively Brazilian biome where plants adapt to a specific series of weather conditions and therefore become a great storehouse of the terpenoid compounds to be described herein. Fungal infections have become increasingly common, and a great demand for new agents with low toxicity and side effects has thus emerged. Scientists must search for new molecules exhibiting antifungal activity to develop new drugs. This review aims to analyze scientific data from the principal published studies describing the use of terpenes and their biological applications as antifungals.

Caused by fungi of the genus Candida spp., candidiasis is reported as a public health problem, causing superficial and systemic infections. The increase in isolated resistant strains and the high toxicity of conventional antifungal agents have stimulated the search for alternatives to this scenario, such as bioproducts or isolated compounds, such as terpenes. Thus, it is important to investigate the antifungal activity of α-pinene alone and in association with antifungals against strains of Candida albicans. For this, the Minimum Inhibitory Concentration (MIC) and the Minimum Fungicide Concentration (MFC) were determined by the technique of microdilution in broth of the isolated terpene and the association assay (checkerboard) between α-pinene and antifungals, such as fluconazole and amphotericin. B. The α-pinene had a MIC between 128 and 512 µg/mL and the CFM had the same MIC values ​​against the 8 strains tested. The other concentrations could not determine the CFM, due to the fungal growth being greater than or equal to MICx4 (test limit). In the association trial, the interaction between α-pinene and fluconazole was indifferent, whereas the combinations between α-pinene with amphotericin B and nystatin obtained synergistic effects. Thus, this study strengthens α-pinene as a promising antifungal agent, as it exhibited strong inhibitory activity against Candida albicans strains, with a fungicidal nature. Additionally, it may be used in association with polyene derivatives (amphotericin B or nystatin) as an alternative in the treatment of candidiasis. It should be noted that more studies need to be carried out on the mechanism of action and toxicity of this compound.

Introdução: A candidíase está relacionada a uma grande variedade de manifestações clínicas que se expressam desde infecções na pele e mucosas à infecção sistêmica. Sendo esta última associada a uma alta taxa de mortalidade global, variando de 36% a 63% em diferentes grupos de pacientes. A terapêutica de infecções fúngicas invasivas é limitada pois há apenas três classes de fármacos convencionais utilizados. Diante deste cenário, estratégias de uso racional dos antifúngicos e busca de novas alternativas terapêuticas se fazem necessárias. Objetivo: Avaliar a atividade antifúngica in vitro do monoterpeno di-hidrojasmona frente cepas de Candida albicans e Candida parapsilosis fluconazol resistentes. Metodologia: As concentrações inibitórias mínimas (CIM) e fungicida mínima (CFM) foram determinadas pelo método de microdiluição. Posteriormente foi observado se a ação antifúngica de di-hidrojasmona ocorre via parede celular (ensaio com sorbitol) ou via membrana (ensaio com ergosterol exógeno). Resultados: A di-hidrojasmona apresentou uma CIM entre 128 - 256 µg/mL e a CFM teve os mesmos valores de CIM, respectivamente. No ensaio com ergosterol exógeno, a CIM da di-hidrojasmona aumentou na presença do ergosterol exógeno sugerindo que o mecanismo de ação do monoterpeno ocorre a partir de sua ligação ao ergosterol presente na membrana. Não houve alteração frente ao uso do sorbitol. Conclusão: Baseado nestes resultados, o presente estudo demonstra que di-hidrojasmona possui forte atividade antifúngica e sugere que esta atividade esteja relacionada a sua ligação ao ergosterol da membrana fúngica. Logo, di-hidrojasmona demostra ser um promissor bioproduto na busca de alternativas para o tratamento das candidíases.

The Candida albicans species is part of the human microbiota and is associated with different types of infections. It is the most commonly isolated yeast in samples of oral cavity infections. The number of infections attributed to the Candida genus has grown significantly on a global scale and due to the rigorous and improper use of current antimicrobials, antimicrobial resistance has also increased. Pogostemon cablin Benth., popularly known as patchouli, is a medicinal herb of great relevance, with several pharmacological properties reported in the literature. The aim of this study was to evaluate the antifungal potential of P. cablin essential oil against 11 oral isolates of Candida albicans and a standard strain (ATCC90028). The chemical characterization of P.cablin was carried out using Gas Chromatography coupled with Mass Spectrophotometry (GC-MS) and 19 molecules were identified, including patchouli alcohol (15.11%), Δ-Guaiene (9.85%), α-Guaiene (8.06%) and α-Patchoulene (5.03%). The antifungal activity was analyzed using the microdilution technique to determine the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC). The mechanism of action of the possible antifungal activity of the phytocomplex in question was analyzed using the sorbitol and ergosterol assays. In addition, some virulence factors were also investigated, such as biofilm formation capacity and morphogenesis. P. cablin showed MIC and MFC values between 2 and 128 µg/mL for the strains tested. The results suggest that this activity occurs through the complexation of the oil's constituents with the ergosterol of the fungal membrane. The essential oil slightly reduced the Morphology Index (MI) of the strains tested. For the most filamentous strain, there was a significant decrease in filament length, from 285.0 µm to 220.5 µm. In the formation of biofilms, the essential oil showed a reduction of 26% to 59% at concentrations of 4 to 40 µg/mL and in the reduction of biofilms formed, the values ranged from 49% to 68%. The essential oil of P. cablin showed a complex chemical composition and significant activity on C. albicans, which was considered fungicidal for most of the strains tested. It is suggested that this antifungal action is due to the complexation of the essential oil with the ergosterol of the fungal plasma membrane. In addition, P. cablin acted on the formation and reduction of biofilm and also exerted an influence on the morphogenesis of Candida albicans.