| Summary: | Two new 4-hydroxy-2-pyridone alkaloids furanpydone A and B (<b>1</b> and <b>2</b>), along with two known compounds N-hydroxyapiosporamide (<b>3</b>) and apiosporamide (<b>4</b>) were isolated from the endophytic fungus <i>Arthrinium</i> sp. GZWMJZ-606 in <i>Houttuynia cordata</i> Thunb. Furanpydone A and B had unusual 5-(7-oxabicyclo[2.2.1]heptane)-4-hydroxy-2-pyridone skeleton. Their structures including absolute configurations were determined on the basis of spectroscopic analysis, as well as the <i>X</i>-ray diffraction experiment. Compound <b>1</b> showed inhibitory activity against ten cancer cell lines (MKN-45, HCT116, K562, A549, DU145, SF126, A-375, 786O, 5637, and PATU8988T) with IC<sub>50</sub> values from 4.35 to 9.72 µM. Compounds <b>1</b>, <b>3</b> and <b>4</b> showed moderate inhibitory effects against four Gram-positive strains (<i>Staphylococcus aureus</i>, methicillin-resistant <i>S. aureus</i>, <i>Bacillus Subtilis</i>, <i>Clostridium perfringens</i>) and one Gram-negative strain (<i>Ralstonia solanacarum</i>) with MIC values from 1.56 to 25 µM. However, compounds <b>1</b>–<b>4</b> showed no obvious inhibitory activity against two Gram-negative bacteria (<i>Escherichia coli</i> and <i>Pseudomonas aeruginosa</i>) and two pathogenic fungi (<i>Candida albicans</i> and <i>Candida glabrata</i>) at 50 µM. These results show that compounds <b>1</b>–<b>4</b> are expected to be developed as lead compounds for antibacterial or anti-tumor drugs.
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