Abstract:Abstract: Objective To investigate the secondary metabolites of two strains of Nesterenkonia sp. N267 and Micromonospora echinofuscaT DSM 43913 from the Zhanjiang Mangrove Nature Reserve in Guangdong Province. Methods The fermented crude extracts were isolated and purified by silica gel column chromatography, thin layer chromatography (TLC) and high performance liquid chromatography (HPLC), respectively. Their structures were identified by modern spectroscopic methods such as nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS) and compared with relevant literature data. Results Ten compounds were isolated from those two strains of actinomycetes. Especially, compounds 1-6 were cyclic dipeptides: cyclo-(l-Pro-l-Leu) (1), cyclo-(l-Pro-l-Val) (2), cyclo-(l-Pro-l-Phe) (3), cyclo-(d-Pro-d-Phe) (4), cyclo-(Gly-l-Phe) (5), cyclo- (l-Pro-l-Tyr) (6), phenylalanine (7), pyridoxine (8), 3,3-di(1H-indol-3-yl) propane-1, 2-diol(9), pyrocatechol (10). The cytotoxic activities of compounds 1-6 and 9 were evaluated toward various human cancer cells, respectively. Compounds 1-6 exhibited no obvious cytotoxic activity at initial screening concentration of 50 μmol/L, while compound 9 exhibited moderate cytotoxic activity with an IC50 values ranging from (42.32 ± 3.64) to (48.35 ± 5.28) μmol/L. Conclusion Compounds 1-5 were found from Nesterenkonia for the first time, while compounds 4 and 6-10 were found from Micromonospora for the first time. Compound 9 showed moderate anti-tumor activity.
