Synergic Effect of Phthalide Lactones and Fluconazole and Its New Analogues as a Factor Limiting the Use of Azole Drugs against Candidiasis

Fungistatic Effect of Phthalide Lactones on Rhodotorula mucilaginosa

Currently, there is an increasing number of cases of fungal infections caused by opportunistic strains of the yeast Rhodotorula mucilaginosa, mainly in immunocompromised patients during hospitalization. The excessive use of antibiotics and azole compounds increases the risk of resistance to microorganisms. A new alternative to these drugs may be synthetic phthalide lactones with a structure identical to or similar to the natural ones found in celery plants, which show low toxicity and relatively high fungistatic activity. In the present study, the fungistatic activity of seven phthalide lactones was determined against R. mucilaginosa IHEM 18459. We showed that 3-n-butylidenephthalide, the most potent compound selected in the microdilution test, caused a dose-dependent decrease in dry yeast biomass. Phthalide accumulated in yeast cells and contributed to an increase in reactive oxygen species content. The synergistic effect of fluconazole resulted in a reduction in the azole concentration required for yeast inhibition. We observed changes in the color of the yeast cultures; thus, we conducted experiments to prove that the carotenoid profile was altered. The addition of lactones also triggered a decline in fatty acid methyl esters.

Chemo-enzymatic synthesis and biological activity evaluation of propenylbenzene derivatives

Propenylbenzenes, including isosafrole, anethole, isoeugenol, and their derivatives, are natural compounds found in essential oils from various plants. Compounds of this group are important and valuable, and are used in the flavour and fragrance industries as well as the pharmaceutical and cosmetic industries. The aim of this study was to develop an efficient process for synthesising oxygenated derivatives of these compounds and evaluate their potential biological activities. In this paper, we propose a two-step chemo-enzymatic method. The first step involves the synthesis of corresponding diols 1b-5b from propenylbenzenes 1a-5avia lipase catalysed epoxidation followed by epoxide hydrolysis. The second step involves the microbial oxidation of a diasteroisomeric mixture of diols 1b-5b to yield the corresponding hydroxy ketones 1c-4c, which in this study was performed on a preparative scale using Dietzia sp. DSM44016, Rhodococcus erythropolis DSM44534, R. erythropolis PCM2150, and Rhodococcus ruber PCM2166. Application of scaled-up processes allowed to obtain hydroxy ketones 1-4c with the following yield range 36-62.5%. The propenylbenzene derivatives thus obtained and the starting compounds were tested for various biological activities, including antimicrobial, antioxidant, haemolytic, and anticancer activities, and their impact on membrane fluidity. Fungistatic activity assay against selected strains of Candida albicans results in MIC₅₀ value varied from 37 to 124 μg/mL for compounds 1a, 3a-c, 4a,b, and 5a,b. The highest antiradical activity was shown by propenylbenzenes 1-5a with a double bond in their structure with EC₅₀ value ranged from 19 to 31 μg/mL. Haemolytic activity assay showed no cytotoxicity of the tested compounds on human RBCs whereas, compounds 2b-4b and 2c-4c affected the fluidity of the RBCs membrane. The tested compounds depending on their concentration showed different antiproliferative activity against HepG2, Caco-2, and MG63. The results indicate the potential utility of these compounds as fungistatics, antioxidants, and proliferation inhibitors of selected cell lines.