Antimicrobial activity of 2-tert-butyl-1.4-benzoquinone and its selected alkylthio and arylthio derivatives.

Abstract

Background: Biologically active compounds, originating from a variety of natural sources: plants, animals and microor- ganisms, have great potential for use as antimicrobial agents. Avarol, a compound originating from the Mediterranean sponge Disidea avara, exhibits a number of biological activities including antimicrobial activity. Considering that, avarol was taken as a model for the synthesis of 2-tert-butyl-1,4-benzoquinone (TBQ) derivatives. Objectives: TBQ was chosen because of its similar chemical structure with avarol who showed strong biological activity but is more accessible and economical than avarol. By selecting the thiol group, we aimed at combining the action of two strong functional groups of natural origin, quinones and thiols, which both have antimicrobial activity. Methods: In this work antimicrobial activity of TBQ and its derivatives: 2-tert-butyl-5-(isopropylthio)-1.4-benzoqui- none, 2-tert-butyl-5-(propylthio)-1.4-benzoquinone, 2-tert-butyl-5,6-(ethylendithio)-1.4-benzoquinone, 2-tert-bu- tyl-5-(phenylthio)-1.4-benzoquinone and 2-tert-butyl-6-(phenylthio)-1.4-benzoquinone was evaluated by the MIC mi- crodilution method on 7 different ATCC bacterial strains. Results: All compounds tested showed stronger antimicrobial activity against Gram positive bacterial strains (Entero- coccus faecalis, Staphylococcus aureus, Bacillus spp.). A strong antimicrobial effect (MIC value less than 100μM) was shown by 2-tert-butyl-5,6- (ethylendithio)-1,4-benzoquinone, 2-tert-butyl-5-(phenylthio)-1.4-benzoquinone deriva- tives and 2-tert-butyl-6-(phenylthio)-1,4-benzoquinone against S.aureus. TBQ, 2-tert-butyl-5-(isopropylthio)-1,4-ben- zoquinone, 2-tert-butyl-5, 6-(ethylendithio)-1,4-benzoquinone and 2-tert-butyl-5-(phenylthio)-1.4-benzoquinone showed strong antimicrobial effect against Bacillus spp. According to our results, chemical modifications of TBQ in- crease its antimicrobial activity while derivative 2-tert-butyl-5,6-(ethylendithio)-1.4-benzoquinone is the best candi- date for further testing