Thioterpenoids of the Bornane Series with Potent Activity Against Opportunistic Micromycetes

Antifungal medicines currently used clinically become less efficient regarding microscopic fungi due to new infectious agents emerging among fungi and a wide range of pathogenic factors in micromycetes. In developing new antifungal medicines, a comprehensive approach is needed that would consider the adaptive properties of fungi. This paper aims to study the antifungal activity of the synthesized compounds on yeast and mycelial fungi. In our study, we assessed the changes in the pathogenic factors of fungi, such as germination and hypha-forming intensity and sporulation, while cultivating them as affected by the compounds under study. This manuscript describes the antifungal activity of the bornane series thioterpenoids. Compound 8 demonstrated a strong antimycotic activity on all fungi species, including Candida albicans (laboratory and clinical stains), Aspergillus niger , and Fusarium solani (MIC 12, 24, 94, and 94 μg/ml, respectively). A. niger sporulation index analysis demonstrated the highest spore production rate at day 6 of culturing in non-treated samples (control) and in those treated with compounds 3 , 6 , and 7 , whereas the highest sporulation of A. niger cultured in the presence of compound 8 was substantially delayed and observed on day 10 of culturing. The lowest level of fungi reproduction was observed over the entire period of experiments for the cultures treated with terbinafine or compound 8 . In addition, compound 8 , fluconazole, and terbinafine had an inhibitory effect on the germination tubes of C. albicans at a concentration of ½ MIC.