Abstract

The isoquinolines are of great importance to humanity because of their medicinal value and different structure. There have been many researches on the isoquinolines, but relatively few pure compounds have been investigated for their antibacterial activity. The in vitro activity of a novel synthetic antimicrobial compound1-(4-choloro-phenyl)-6,7-dimethoxy-2-methyl-1,2,3,4, tetrahydroisoquinoline was evaluated against Pseudomonas aeruginosa(ATCC27853) using standard methods approved by Clinical and Laboratory Standards Institute. The minimum inhibitory concentration of the compound which inhibited more than 90% growth (MIC₉₀) of P. aeruginosa was found to be ranged from 24.0 to 6.0 mg ml^-1 in different media. The ET₅₀ (concentration which lyses 50% erythrocytes) of the compound was observed to be 450 mg ml^-1. It was found that the compound down-regulated the expression of PQS, elastase and pyocyanin, the important virulence factors of P. aeruginosa. Proteomics studies revealed that the compound inhibited/down regulated the expression of PhnA and oprL proteins of P. aeruginosa which are crucial for PQS synthesis and membrane integrity. This type of compounds may provide avenue for the discovery of clinically useful antibacterial drugs.

Key words: Isoquinoline, P. aeruginosa, virulent factors, antimicrobial activity, proteomics.