Limonin 7-methoxime interferes with Escherichia coli biofilm formation and attachment in type 1 pili and antigen 43 dependent manner

Citrus limonoids were reported to inhibit autoinducer-mediated bacterial cell–cell signaling, Escherichia coli O157:H7 biofilms and the Type III secretion system. The goal of the present study was to understand the effect of specific modifications in limonin molecule on cell–cell signaling inhibitory activity. The limonin was modified into de-furan limonin, limonin 7-oxime, limonin 7-methoxime. The modified limonoids were examined for their cell–cell signaling and biofilm inhibitory properties. The results of the study suggest that the furan ring and C-7 substitutions were important structural features in the limonin molecule to inhibit cell–cell signaling and biofilm formation in Vibrio harveyi. The C-7 modifications of limonin showed increased potency to inhibit the E. coli biofilm. Furthermore, the data indicates that limonin 7-methoxime reduced the attachment of E. coli to plastic surface by interacting with type 1 pili and Ag43. In addition, limonin 7-methoxime seems to reduce the adhesion of E. coli to spinach leaves and colon epithelial cells.