Violacein is a bacterial metabolite originally isolated from C. violaceum that has antibacterial and antiprotozoal activities.[1] [2] It is produced by C. violaceum as a purple pigment in response to N-hexanoyl homoserine lactone , a property that has been modified to create a strain of C. violaceum used in detecting quorum-sensing molecules.[3] Violacein is active against Gram-positive bacteria, including B. subtilis and S. aureus (MICs = 0.8 and 1.6 &#181M, respectively). It is also active against P. falciparum, including chloroquine-susceptible and -resistant strains (IC50s = 0.85 and 0.63 &#181M, respectively).[2] It reduces parasitemia in a mouse model of nonlethal P. chabaudi chabaudi infection when administered at a dose of 7.5 mg/kg and increases survival in a mouse model of lethal P. chabaudi chabaudi infection. Violacein permeabilizes the cytoplasmic membrane of bacterial cells but does not affect the cell wall.[1]

Reference:
[1]. Cauz, A.C.G., Carretero, G.P.B., Saraiva, G.K.V., et al. Violacein targets the cytoplasmic membrane of bacteria. ACS Infect. Dis. 5(4), 539-549 (2019).
[2]. Lopes, S.C.P., Blanco, Y.C., Justo, G.Z., et al. Violacein extracted from Chromobacterium violaceum inhibits Plasmodium growth in vitro and in vivo. Antimicrob. Agents Chemother. 53(5), 2149-2152 (2009).
[3]. Blosser, R.S., and Gray, K.M. Extraction of violacein from Chromobacterium violaceum provides a new quantitative bioassay for N-acyl homoserine lactone autoinducers. J. Microbiol. Methods 40(1), 47-55 (2000).