Roseoflavin is an analog of flavin mononucleotide (FMN) and riboflavin with antimicrobial activity. Roseoflavin is converted to the flavin mononucleotide (FMN) analog roseoflavin mononucleotide (RoFMN) by flavokinase and to the flavin adenine dinucleotide (FAD) analog roseoflavin adenine dinucleotide (RoFAD) by FAD synthetase, and acts as a riboflavin antagonist. Roseoflavin is an inhibitor of bacterial riboflavin riboswitches, cis regulatory elements present in non-coding RNA that specifically bind to natural ligands to regulate gene expression. Roseoflavin, converted to RoFMN, blocks the flavin mononucleotide riboswitch-mediated expression of the ribB gene, which is required for riboflavin biosynthesis.