Bioactive secondary metabolites from tomato-derived bacterium Bacillus velezensis Hnu24

A series of secondary metabolites have been isolated from the genus of Bacillus velezensis, most of which show antibacterial and insecticidal activities. In order to find more bioactive secondary metabolites from B. velezensis, one new natural component aminoindole dimer baciindole A (1), together with seven known compounds (2-8) were isolated from the tomato-derived bacterium Bacillus velezensis Hnu24. The structure of compound 1 was elucidated by its HR-ESI-MS spectral data and 1 D/2D NMR spectroscopic analysis. Compound 3 showed antibacterial activity against Staphylococcus aureus, S. epidermidis and Ralstonia solanacearum with the MIC values of 3.125, 12.5 and 50 μg/mL, respectively. Compound 4 showed antibacterial activity against S. aureus with the MIC value of 12.5 μg/mL. Compound 3 showed cytotoxic activity for human colon cancer HTC116 cancer cells with the IC₅₀ value of 8.42 ± 0.48 μM. Five compounds (1-4 and 8) were obtained from the strain of B. velezensis for the first time. These results indicated that 3 will be useful in developing antimicrobial and treatment of colon cancer agents.