Polyketide compounds in the liquid culture of endophyte Alternaria sp.QDFB-2 from Ficus carica L.

Objective To investigate the polyketide compounds in the liquid culture of endophyte Alternaria sp.QDFB-2 from Ficus carica L. and evaluate their in vitro cytotoxicity.

Methods The chemical constituents in the fermentation broth of Alternaria sp.QDFB-2 were fractionated and purified through multiple chromatographic methods such as silica gel column, Sephadex LH-20 gel column, ODS reserved phase columnand high performance liquid chromatography. Then, structures of obtained compounds were determined by modern spectroscopy methods including nuclear magnetic resonance (NMR) and high resolution mass spectrometry (HR-MS) and comparison with literature. Finally, the cytotoxicity of these compounds was evaluated by Methyl Thiazolyl Tetrazolium (MTT) method.

Results Seven polyketide compounds were obtained from the crude extract of liquid culturefrom Alternaria sp.QDFB-2 and identified as 7-hydroxy-2, 5-dimethyl-4H-1-benzopyran-4-one (1), 1-deoxyrubralactone (2), alternariol-9-O-monomethyl ether (3), alternariol (4), altenuisol (5), stemphyperylenol (6) and altertoxin Ⅰ (7), respectively. The in vitro cytotoxicity assay showed that compound 4 had significant inhibition activity against human cervical carcinoma cell line HeLa and human hepatocellular carcinoma cell line SMMC-7721, with half-maximal inhibitory concentration (IC₅₀) values of 13.43 and 50.47 μg/mL, respectively.

Conclusion Alternaria sp.QDFB-2 could produce abundant polyketide compounds, which is worthy of further research in developing drugs from microorganism.