Study on secondary metabolites of endophytic fungus Diaporthe sp. AC1 induced by tryptophan analogs

Shikai Zhang; Qing Xu; Changbo Ji; Xiaoyu Han; Yang Zhou; Chao Liang; Linran Ma; Weijian Sun; Yanling Li; Zhengyou Yang; Fengchun Zhao; Yuan Tian

doi:10.3389/fmicb.2023.1254609

Study on secondary metabolites of endophytic fungus Diaporthe sp. AC1 induced by tryptophan analogs

Front Microbiol. 2023 Oct 9:14:1254609. doi: 10.3389/fmicb.2023.1254609. eCollection 2023.

Authors

Shikai Zhang¹, Qing Xu¹, Changbo Ji², Xiaoyu Han², Yang Zhou², Chao Liang², Linran Ma², Weijian Sun², Yanling Li², Zhengyou Yang¹, Fengchun Zhao¹, Yuan Tian²

Affiliations

¹ Department of Microbiology, College of Life Science, Key Laboratory for Agriculture Microbiology, Shandong Agricultural University, Taian, China.
² College of Life Science, Shandong First Medical University & Shandong Academy of Medical Sciences, Taian, China.

Abstract

Small molecule-induced fermentation of the endophytic fungus Diaporthe sp. AC1 originated from Artemisia argyi was executed to investigate its secondary metabolites. It was fermented in a culture medium containing 5-hydroxytryptophan (5-HTP), 1-methyl-L-tryptophan (1-MT), and tryptamine (TA), respectively. The antibacterial activities of crude extracts against pathogenic bacteria and pathogenic fungi were determined by using the Oxford cup method, while the cytotoxicity of crude extracts against cancer cells was determined by using the MTT method. The results showed that the secondary metabolites of Diaporthe sp. AC1 induced by 1-MT exhibited optimal antibacterial activity and tumor cytotoxicity. The induction conditions of 1-MT were optimized, and the antibacterial activities and tumor cytotoxicity of crude extracts under different induction conditions were investigated. As indicated, the optimal moment for 1-MT addition was before inoculation and its optimal concentration was 0.25 mM. Under these conditions, Diaporthe sp. AC1 was fermented and approximately 12 g of crude extracts was obtained. The crude extracts were then separated and purified to acquire nine monomer compounds, including three new compounds (1-3) and six known compounds (4-9). The antibacterial activities of the compounds against pathogenic bacteria and pathogenic fungi were investigated by using the microdilution method, while their cytotoxicity against cancer cells was analyzed by using the MTT method. The results demonstrated that Compound 1 exhibited moderate antibacterial activities against Verticillium dahlia, Fusarium graminearum, and Botrytis cinerea, as well as a low inhibitory activity against Listeria monocytogenes. Nevertheless, Compound 1 showed significant cytotoxicity against five cancer cells, with IC₅₀ ranging from 12.26 to 52.52 μM. Compounds 2 and 3 exhibited negligible biological activity, while other compounds showed detectable inhibitory activities against pathogenic bacteria and cancer cells.

Keywords: 1-methyl-L-tryptophan; Diaporthe; biological activity; endophytic fungi; secondary metabolites.

Grants and funding

This work was supported by the Youth Science Foundation Program of Shandong First Medical University (202201-034), Shandong Medical and Health Science and Technology Development Project (202101060623), the National Natural Science Foundation of China (21602152) and the Student Research Training Program of Shandong First Medical University (2022104391502, 2022104391556, 202310439014 and 202310439002).