Journal
PEST MANAGEMENT SCIENCE
Volume 77, Issue 5, Pages 2264-2271Publisher
JOHN WILEY & SONS LTD
DOI: 10.1002/ps.6251
Keywords
Alternaria alternata; secondary metabolites; enantiomers; antibacterial activity
Categories
Funding
- National Key Research and Development Program of China [2017YFD0200500]
- National Natural Science Foundation of China [32072443, 21602109, 31572043]
- Natural Science Foundation of Jiangsu Province [BK20201323]
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This study focused on the discovery of bioactive polyketides from endophytic Alternaria alternata ZHJG5, highlighting their structural elucidation and antibacterial activities. The newly isolated compounds showed pronounced antibacterial activity against phytopathogenic bacteria, suggesting their potential as candidates for novel bactericides.
BACKGROUND Phytopathogenic bacteria, such as Xanthomonas oryzae pv. oryzae (Xoo) and Ralstonia solanacearum (Rs), seriously threaten crop production and are the cause of enormous yield losses. Endophytic fungi are abundant sources of bioactive metabolites that may be potential candidates in the development of new agrochemicals. This work emphasizes the discovery of bioactive polyketides from endophytic Alternaria alternata ZHJG5 and reports their structural elucidation and antibacterial activities in detail. RESULTS Five novel polyketide derivatives, isotalaroflavone (2), (+/-)-5 '-dehydroxytalaroflavone (3a/3b), (+)-talaroflavone (4b), and bialternacin G (7), along with five known compounds (1, 4a, 5, 6, and 8), were obtained from the Cercis chinensis-derived fungus A. alternata ZHJG5. The compounds' structures were characterized using spectroscopic methods and X-ray diffraction. Chiral high-performance liquid chromatography was used to separate the racemates 3 and 4, whose absolute configurations were unambiguously confirmed by comparing their experimental and calculated electron circular dichroism data. All isolated compounds were tested for antibacterial activity against the phytopathogenic bacteria Xoo, Xanthomonas oryzae pv. oryzicola (Xoc) and Rs. Compounds 1, 2 and 8 showed pronounced antibacterial activity against all tested bacteria, with minimal inhibitory concentrations ranging from 0.5 to 64 mu g/ml. In addition, compound 1 showed a potent protective effect against rice bacterial leaf blight caused by Xoo with a protective efficacy of 75.1% at a concentration of 200 mu g/ml. CONCLUSION These findings highlight the practical potential of antibacterial compounds as candidates for the discovery of novel bactericides.
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