Unveiling the anti-Candida albicans activity of bioactive fractions from mining soil-dwelling Streptomyces sp. DS104

Abstract

Due to an increase in the incidence of Candida albicans infection and its growing resistance to currently used antifungal drugs, further development of more potent antimicrobials is needed. This study sought to assess the antifungal properties of Streptomyces sp. DS104, isolated from a mining soil, against C. albicans and identify the bioactive substances that are produced by this strain. Ethyl acetate supernatant's crude extract showed a high inhibition against C. albicans, with a minimal inhibitory concentration value as low as 4 µg/mL. Two bioactive fractions (F5 and F6) have been isolated using silica gel column chromatography, demonstrating zones of inhibition against C. albicans measuring 28.33 ± 01.52 to 29.00 ± 02.64 mm. The GC–MS analysis was carried out on the purified fractions and allowed the identification of 21 compounds predominantly consisting of carboxylic acids and pyrrolopyrazine derivatives. In Fraction F5, the major compounds detected are pentadecanoic and hexadecanoic acids, constituting the highest area percentages of 41.99 % and 33.77 %, respectively. As for fraction F6, the predominant compounds include pyrrolo[1,2-a]pyrazine-1,4‑dione, hexahydro-3-(2-methylpropyl) and pyrrolo[1,2-a]pyrazine-1,4‑dione, hexahydro-3-(methylphenyl), accounting for area percentages of 20.18 % and 12.16 %, respectively. Various other bioactive compounds, such as isocoumarins, and phenolic compounds, had previously been identified as components with antifungal activity, were also detected. It's worth highlighting that three compounds specifically, 2-hydrazino-8‑hydroxy-4-phenylquinoline, hydroxyphenylacetic acid, and 3-carboxaldehyde-1H-indole have been reported for the first time to be detected within the Streptomyces genus. These results suggested that Streptomyces sp. DS104 is a promising strain and thus appears to be a potential candidate for the development of antifungal drugs.

Keywords

• Streptomyces
• Mining soil
• Candida albicans
• Anti-C. albicans activity
• GC-MS
• Bioactive compounds