Three new methylated Δ8-pregnene steroids, stemphylisteroids A-C (1-3) were isolated from the medicinal plant Polyalthia laui-derived fungus Stemphylium sp. AZGP4-2. Their structures were elucidated by the detailed analysis of comprehensive spectroscopic data. The absolute configuration of 1 was determined by X-ray crystallographic analysis. Compound 1 show antibacterial activity against Escherichia coli with the MIC value of 6.25 μg/mL, and 2 exhibited a broad spectrum of antibacterial activities against six pathogenic bacteria with the MIC values ranging from 12.5 to 50 μg/mL. The discovery of three methylated Δ8-pregnene steroids 1-3 are a further addition to diverse and complex array of methylated steroids.
Keywords: Antibacterial activity; Methylated Δ(8)-pregnene steroids; Polyalthia laui; Stemphylium sp..
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