Indole Derivatives and a Diketopiperazine from Chromobacterium violaceum

Three indole derivatives (1–3) and a diketopiperazine (4) were isolated from the ethyl acetate extract of Chromobacterium violaceum. Their structures were elucidated based on the analysis of NMR and HR-MS data and by comparing those in the previous literature. The antibacterial activities of the isolated compounds were evaluated against Gram-positive bacteria, including human pathogenic methicillinresistant Staphylococcus aureus (MRSA), Lacticaseibacillus paracasei subsp. paracasei, and Brevibacterium epidermidis. Compound 1 exhibited moderate antibacterial activity against all the three strains with MIC values ranging from 8.58 to 34.3 μg/mL.