Chemical investigation of a strain Streptomyces sp. KIB-H1318 isolated from soil sample led to the discovery of three new phenoxazinone-related alkaloids 1–3, as well as two known analogs exfoliazone (4) and viridobrunnine A (5). Their structures were determined on the basis of extensive spectroscopic analysis. The antimicrobial activity and cytotoxicity of the isolates were assayed. Exfoliazone and viridobrunnine A exhibited minor antibacterial activity against Escherichia coli ATCC 8099, Bacillus subtilis ATCC 6633, and Staphylococcus aureus ATCC 6538. Compound 2 exhibited low cytotoxicity against two human cancer cell lines HeLa and SW480 with the IC50 values of 36.8 and 37.8 μM, respectively.
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This research was financially supported by the National Natural Science Foundation of China to S-X.H. (Nos. U1702285 and 81522044), Yunnan Innovative Research Team for Discovery and Biosynthesis of Bioactive Natural Products (2018HC012), High-end Science and Technology Talents Program of Yunnan Province to S-X.H. (No. 2013HA022), and Key Research Program of Frontier Sciences, CAS (No. QYZDB-SSW-SMC051).
Conflict of interest
The authors declare that they have no conflict of interest.