Ribocil-C is a selective inhibitor of the bacterial riboflavin riboswitch, acting as a synthetic analogue of flavin mononucleotide (FMN). It suppresses ribB gene expression and inhibits bacterial cell growth.

Ribocil-C is a highly selective inhibitor targeting the flavin mononucleotide (FMN) riboswitch and can regulate gene expression in the de novo biosynthesis pathway of riboflavin (RF, vitamin B₂) in Escherichia coli. Additionally, it specifically acts on dual FMN riboswitches, which respectively control RF biosynthesis essential for Staphylococcus aureus growth and pathogenic processes, as well as RF uptake [1].
As a synthetic small-molecule analog of FMN, Ribocil-C binds to the FMN riboswitch in various Gram-negative (GN) bacteria (including Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii), exerting antibacterial effects by suppressing ribB gene expression and RF synthesis [1][2].

Ribocil-C (60 mg/kg and 120 mg/kg) showed significant dose-dependent antibacterial effects, lowering the bacterial load (CFU/g) in the spleen by 1.87 and 3.29 log₁₀, respectively, compared to untreated control mice. Additionally, no significant mortality or toxic reactions were observed [2].