Secondary metabolites of Bacillus coagulans LL1103 from large yellow croaker (Pseudosciaena crocea)

Abstract:

[Objective] To mine new antimicrobial agents from Bacillus coagulans LL1103 isolated from large yellow croaker.[Methods] The ethyl acetate and n-butanol extracts of B. coagulans LL1103 fermentation broth were separated and purified by chromatographic techniques, and their structures were identified based on spectral analysis. Their antibacterial activities were detected by micro-broth dilution method. [Results] From the fermentation broth of B. coagulans LL1103, 9 cyclic dipeptides (1-9) were obtained as (1) cyclo-(4-Hydroxyl-Pro-Leu), (2) cyclo-(Ile-Ala), (3) cyclo-(Pro-Val), (4) cyclo-(Pro-Phe), (5) cyclo-(Pro-Leu), (6) cyclo-(Gly-Ala), (7) cyclo-(Pro-Gly), (8) cyclo-(Pro-Ala) and (9) cyclo-(Tyr-Gly). Cyclic dipeptides 3, 7 and 9 showed strong antibacterial activities against Escherichia coli with minimal inhibitory concentration values of 8.0, 4.0 and 16.0 μg/mL, respectively. [Conclusion] Three compounds showed remarkably biological effect on the growth of E. coli.