Capisterones A and B, which Enhance Fluconazole Activity in Saccharomyces cerevisiae, from the Marine Green Alga Penicillus capitatus

Abstract

A whole cell-based assay using Saccharomyces cerevisiae strains that overexpress Candida albicans CDR1 and MDR1 efflux pumps has been employed to screen natural product extracts for reversal of fluconazole resistance. The tropical green alga Penicillus capitatus was selected for bioassay-guided isolation, leading to the identification of capisterones A and B (1 and 2), which were recently isolated from this alga and shown to possess antifungal activity against the marine pathogen Lindra thallasiae. Current work has assigned their absolute configurations using electronic circular dichroism and determined their preferred conformations in solution based on detailed NOE analysis. Compounds 1 and 2 significantly enhanced fluconazole activity in S. cerevisiae, but did not show inherent antifungal activity when tested against several opportunistic pathogens, or cytotoxicity to several human cancer and non-cancerous cell lines (up to 35 μM). These compounds may have a potential for combination therapy of fungal infections caused by clinically relevant azole-resistant strains.The molecular mechanisms of antifungal drug resistance may involve a variety of factors such as mutation of target genes and decreased drug concentrations in the cells due to overexpression of efflux pumps. 1,2 In recent years, the rapid development of such drug resistance, particularly for azole antifungals, has highlighted the need for new strategies in antimycotic therapies. 1-5 Efflux pump inhibition has been considered as a promising approach in this regard. Two families of efflux pumps found in Candida albicans include the major facilitators (multidrug resistance, MDR) that are fueled by a proton gradient and the P-glycoprotein ABC transporters (Candida drug resistance, CDR) that require ATP hydrolysis for energy. Within each family, several subtypes have been discovered (i.e., CDR1, CDR2, MDR1). 1,2 We have established a whole cell-based assay using Saccharomyces cerevisiae strains that overexpress C. albicans CDR1 and MDR1 efflux pumps to screen for natural products that can reverse fluconazole resistance and may not be necessarily antifungal. 6In a continuing effort to search for new efflux inhibitors from natural sources, we have screened over 5000 marine extracts from the National Cancer Institute Open Repository. In the presence of a subinhibitory concentration of fluconazole, an extract of the tropical green alga Penicillus capitatus (Halimedaceae) that had an IC 50 value of 55 μg/mL against S. cerevisiae DSY 415 strain (overexpressing the CDR1 efflux pump) and an IC 50 value of < 6 μg/mL against S.

Improved Antitumoral Activity of Extracts Derived from Cultured <i>Penicillus dumetosus</i>

“…Tropical green alga in the order Bryopsidales, including the genus Penicillus are noted for the production of sesqui and diterpenoids that could be responsible of this antiproliferative activity [2]. Triterpene esters capisterones A and B derived from this green alga have also shown potent inhibition on marine fungi [4].…”

“…Tropical green alga in the order Bryopsidales, including those of the genera Avranvillaea, Caulerpa, Halimeda, Penicillus and Udotea, are noted for the production of sesqui and diterpenoids, compounds that have also shown antifungal and antiproliferative activity [2,4]. Recent studies have shown that both aqueous and organic extracts of Penicillus dumetosus exhibit in vitro antiprotozoal [5,6], as well as cytotoxic and antiproliferative activities on cancer cell lines [7].…”

Baker's yeast as a tool for the development of antifungal drugs which target cell integrity – an update

“…Because signaling cascades and other interaction networks also play vital roles in pathogenic fungi, it is to be expected that the yeast two-hybrid system will be applied for inhibitor screens in some of their key components. In this context, heterologous expression of multidrug transporters from C. albicans and some other pathogenic fungi in S. cerevisiae have already been used for the investigation of their mode of action and in screens for specific inhibitors [30,31] . In the latter work, a multiple deletion mutant has been constructed in S. cerevisiae before the expression of the heterologous transporters to reduce the endogenous transport capacity.…”

Evaluation of the In Vitro Cytotoxic Activity of Jania rubens Against Jurkat and Molt-4 Human Cancer Cell Lines

“…6 Recent findings showed that seaweeds also contained antiviral, antibacterial, antifungal and antitumour potentials, among numerous others. [7][8][9][10] Here, in our present study we evaluated the in vitro cytotoxic activity of Jania rubens, a red alga which is found in many parts of the world such as Mediterranean, Black Sea, North-Eastern Atlantic (from Norway to Morocco), Indian Ocean and the China Sea, and has been reported to possess many biological activities such as antibacterial, antifungal, anthelminthic, anticancer, analgesic, antipyretic and anti-inflammatory activities. 11,12 We have tested the methanol extract of the red algae for its potential cytotoxic activity against Jurkat and molt-4 cells which are two kinds of human leukemic cell lines.…”