Quinoline derivatives possess antifungal, antibacterial, antimalaria, anti- HIV, antitumor and herbicidal activities. Antimicrobial activity of novel 4- carboxylic acid quinoline derivatives was thus investigated in this study Overall, these compounds showed a significant antibacterial activity against GPBs such as methicillin-resistant Staphylococcus aureus (MRSA). However, the largest inhibition zone diameters were observed for Bacillus subtilis with 26-38 mm. Zone diameters obtained for C. albicans with about 21 mm was also remarkable. One of these compounds, i.e. 2-(4- (Methylsulfonyl) phenyl) benzo [h] quinoline-4-carboxylic acid could produce the largest inhibition zone with regard to aforementioned microorganisms. Furthermore, these compounds showed to have a weak inhibitory effect (zone diameter of 12-18 mm) on A. niger but almost no activity against GNBs, in particular Pseudomonas aeruginosa.
The diameters of zone inhibition produced by these quinoline compounds were usually larger than those of tobramycin against GPBs and amphotricin B against C. albicans, indicating their significant activity against these microorganisms. Considering the significant growth inhibitory effect on MRSA of test compounds, determination of structure-antimicrobial activity relationship, if any, in order to find related compounds with higher activity is recommended.