Correlation between lipophilicity and antimicrobial activity of some 2-(4-substituted phenyl)-3(2H)-isothiazolones

Abstract

Background and purpose of the study

 
. 3(2H)-Isothiazolones have shown antimicrobial activity and have been used as preservative in different products. However, reports on their structure-antimicrobial activity relationship are scanty. The aim of this study was to determine the relationship between lipophilicity and antimicrobial activity of several 2- (4-substituted phenyl) -3(2H)-isothiazolones of which some have shown antibacterial activities similar or higher than gentamycin, ceftazidime, ceftriaxone, ciprofloxacin , and antifungal activites similar or higher than itraconazole and ketoconazole as reference drugs.Methods. Partition coefficient (log Po/w) of the tested compounds was determined experimentally by a reversed- phase high performance liquid chromatography method using octadecyl-poly(vinyl alcohol) (ODP) column and methanol-water gradient as mobile phase and theoretically by Clog P and ALOGPS computer programs. Results. The HPLC and theoretical log Po/wvalues showed potential correlations which indicate that both experimental and theoretical methods are equally suitable to predict lipophilicity of 3(2H)-isothiazolones. There were also significant correlations between MICs (minimum inhibitory concentrations) of 5-chloro substituted 3(2H)- isothiazolnes against Salmonella typhimurium and Escherichia coli and experimentally determined log Po/wvalues, as well as MICs of 5-unsubstituted 3(2H)- isothiazolnes against E. coli and ALOGPS values. The antifungal activity of the tested compounds against Tricophyton. mentagrophytes and M.canis increased with increase in the experimental and theoretical log P values , but this increase was only significant for the activity against

Microsporum. canis.