What question did this study set out to answer?

To isolate and characterize spirosteroids from Galactomyces pseudocandidus with antifungal properties.

March 5, 2026Journal of Natural Products0 citations

Hexacyclic 6/6/6/5/6/6 Spirosteroids Produced by a Marine-Derived Fungus Galactomyces pseudocandidus and Antifungal Activity against Candida Species

HKHitoshi KamauchiMusashino University MKMikuru KurodaJosai University MSMitsuaki Suzuki

Key Points

To isolate and characterize spirosteroids from Galactomyces pseudocandidus with antifungal properties.
Isolation of epoformsterols A and B from Galactomyces pseudocandidus
Structural elucidation using NMR, HRMS, and single-crystal X-ray diffraction
Determination of antifungal activity against Candida species using MIC and MFC ratios
Assessment of lipase inhibition in a model enzyme assay
Epoformsterols A and B inhibited Candida auris and C. albicans with MIC values of 3.12-12.5 μg/mL
Fungistatic mode of action indicated by MFC/MIC ratios
Epoformsterols A and B inhibited C. rugosa lipase with IC50 values of 5.7 and 8.9 μM, respectively

Abstract

Two spirosteroids, epoformsterols A and B (1 and 2), featuring a highly fused 6/6/6/5/6/6 hexacyclic framework, were isolated from the marine-derived fungus Galactomyces pseudocandidus. The structures of 1 and 2 were elucidated by NMR, HRMS, and single-crystal X-ray diffraction. The absolute configuration of 1 was established by comparison of calculated and experimental ECD spectra, and that of 2 was assigned by ECD comparison with 1. Compounds 1 and 2 exhibited inhibitory activity against Candida auris and C. albicans with MIC values of 3.12-12.5 μg/mL, and MFC/MIC ratios suggested a fungistatic mode of action. Both compounds also inhibited C. rugosa lipase (CRL) in a model enzyme assay, with IC50 values of 5.7 and 8.9 μM, respectively. These results identify a distinctive class of fungal steroids with antifungal activity.

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