Antifungal activity of a trypsin inhibitor from Salvia hispanica L. (chia) seeds against fluconazole-resistant strains of Candida spp. and evaluation of its toxicity in vitro.

The incidence of Candida species resistant to traditional antifungal drugs is increasing globally. This issue significantly impacts patients' lives and increases healthcare expenses, confirming the need to develop novel therapeutic strategies. Recently, a thermostable trypsin inhibitor named ShTI (11.558 kDa), which has antibacterial effects on Staphylococcus aureus, was isolated from Salvia hispanica L. (chia) seeds. This study aimed to assess the antifungal effect of ShTI against Candida species and its synergism with fluconazole and to evaluate its mode of action. Preliminary toxicological studies on mouse fibroblasts were also performed. ShTI exhibited antifungal effects against C. parapsilosis (ATCC® 22,019), C. krusei (ATCC® 6258), and six clinical fluconazole-resistant strains of C. albicans (2), C. parapsilosis (2), and C. tropicalis (2). The minimum inhibitory concentration (MIC) values were 4.1 µM (inhibiting 50% of the isolates) and 8.2 µM (inhibiting 100% of the isolates). Additionally, when combined with fluconazole, ShTI had a synergistic effect on C. albicans, altering the morphological structure of the yeast. The mode of action of ShTI against C. krusei (ATCC® 6258) and C. albicans involves cell membrane permeabilization, the overproduction of reactive oxygen species, the formation of pseudohyphae, pore formation, and consequently, cell death. In addition, ShTI (8.65 and 17.3 µM) had noncytotoxic and nongenotoxic effects on L929 mouse fibroblasts. These findings suggest that ShTI could be a promising antimicrobial candidate, but further research is necessary to advance its application as a novel antifungal agent.

Exploring the Fluconazole-Resistance Modifying Activity and Potential Mechanism of Action of Fixed Oil from Caryocar coriaceum Wittm. (Caryocaraceae) against Candida Species.

The fixed oil from the inner mesocarp of Caryocar coriaceum Wittm. is used in the Chapada do Araripe region of Brazil for the treatment of genitourinary candidiasis. This study aimed to evaluate the chemical composition, antifungal activity, reduction of fungal virulence, and the preliminary toxicity of the fixed oil from the inner mesocarp of C. coriaceum tested against three Candida yeasts. The oil was characterized by gas chromatography (GC-MS and GC-FID). Antifungal activity was assessed using the serial microdilution method. Additionally, the potential of the oil as an enhancer of fluconazole action was tested at sub-inhibitory concentrations (MIC/8). The mechanism of action of C. coriaceum fixed oil was determined by evaluating the inhibition of morphological transition in Candida spp. The chemical composition of the fixed oil of C. coriaceum comprised both unsaturated and saturated fatty acids. Oleic (61 %) and palmitic (33 %) acids were the major constituents. Regarding its anti-Candida activity, the oil inhibited the growth of C. albicans (IC50 : 371 µg/mL) and C. tropicalis (IC50 : 830 µg/mL). Furthermore, the oil reversed the antifungal resistance of C. albicans and C. tropicalis, restoring the susceptibility to fluconazole and reducing their IC50 from 12.33 µg/mL and 362 µg/mL to 0.22 µg/mL and 13.93 µg/mL, respectively. The fixed oil of C. coriaceum completely inhibited the morphological transition of C. albicans and C. tropicalis at a concentration of 512 µg/mL, but exhibited limited low antifungal potential against C. krusei. The observed antifungal activity may be attributed to the overproduction of reactive oxygen species. Additionally, the oil showed no toxic effect on the Drosophila melanogaster in vivo model. The fixed oil from the inner mesocarp of C. coriaceum emerge as a strong candidate for the development of new pharmaceutical formulations to treat infections caused by Candida spp.