Production of New Antibacterial 4-Hydroxy-<i>α</i>-Pyrones by a Marine Fungus <i>Aspergillus niger</i> Cultivated in Solid Medium
2019
Lijian Ding | Lu Ren | Shuang Li | Jingjing Song | Zhiwen Han | Shan He | Shihai Xu
Four 4-hydroxy-<i>α</i>-pyrones including three new ones named nipyrones A−C (<b>1</b>−<b>3</b>) together with one known analogue germicidin C (<b>4</b>) were discovered from a marine sponge-derived fungus <i>Aspergillus niger</i> cultivated in a solid rice culture. Their structures and absolute configurations were elucidated through a combination of spectroscopic data and electronic circular dichroism (ECD) calculations as well as comparison with literature data. Compounds <b>1</b>−<b>4</b> were evaluated for their antibacterial activities against five pathogenic bacteria (<i>Staphylococcus aureus</i>, <i>Escherichia coli</i>, <i>Bacillus subtilis</i>, methicillin-resistant <i>Staphylococcus aureus</i>, and <i>Mycobacterium tuberculosis</i>). Compound <b>3</b> showed promising activity against <i>S. aureus</i> and <i>B. subtilis</i>, with minimum inhibitory concentration (MIC) values of 8 μg/mL and 16 μg/mL, respectively, and displayed weak antitubercular activities against <i>M. tuberculosis</i>, with MIC value of 64 μg/mL, while compounds <b>1</b> and <b>2</b> exhibited moderate antibacterial efficacy against four pathogenic bacteria with MIC values of 32−64 μg/mL.
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