Identification of potential quorum quenching compounds in Brassica oleracea var. capitata against MDR Pseudomonas aeruginosa and Escherichia coli clinical isolates

Over the last decades, the development of microbial resistance has become an alarming situation. This has urged the search for new antimicrobial strategies. In this context, two Brassicaceae edible plants; Brassica oleracea var. capitata (cabbage) and Brassica rapa subsp. rapa (Turnip) were assessed for their antimicrobial activity against P. aeruginosa and E. coli clinical isolates. Antibiogram analysis was done according to the CLSI 2019 guidelines and proved that both P. aeruginosa and E. coli clinical isolates were multidrug resistant. A green extraction methodology – assisted by microwave and ultrasound- was used to prepare the aqueous extracts. Determination of minimum inhibitory concentration (MIC) of the extracts was also carried out according to the CLSI guidelines. At sub-MIC concentration, cabbage extract showed promising results in the inhibition of quorum sensing mediated virulence determinants of P. aeruginosa. Highest reduction was observed in pyocyanin and rhamnolipid production. Chemical profiling via UPLC-ESI-MS analysis of cabbage extract revealed the presence of different glucosinolates together with iberin and sulforaphane. The in silico docking study was conducted and revealed the ability of sulforaphane and iberin to bind to LasR regulator responsible for quorum sensing in P. aeruginosa. These compounds thus represent potential candidates that can be developed into novel antimicrobial infection control tools.