Antimicrobial activity of selected cyclic dipeptides

Cyclic dipeptides are products of rational drug design, which may exhibit b oth antimicrobial and antitumor properties. The aim of this study was to in vestigate both the antimicrobial effects of the cyclic dipeptides cyclo(L-p henylalanyl-L-prolyl), cyclo(L-tyrosyl-L-prolyl), cyclo(L-tryptophanyl-L-pr olyl) and cyclo(L-tryptophanyl-L-tryptophanyl) and the effects of these cyc lic dipeptides on the gastrointestinal epithelium in vitro. Furthermore, a relevant solvent for the possible pharmaceutical application of the product s was sought concurrently The antimicrobial effect of the cyclic dipeptides was assayed using the Kirby-Bauer disc diffusion assay against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae. Staphylococcus aureus , Bacillus subtilis, Streptococcus pneumoniae, Candida albicans, Aspergillu s niger and Penicillium notatum. The effect of the cyclic dipeptides on the gastrointestinal epithelium was assessed by changes in alkaline phosphatas e expression of HT-29 cells. Cyclo(Pro-Trp) and cyclo(Phe-Pro) show broad s pectrum antibacterial properties and cyclo(Trp-Pro) and cyclo(Trp-Trp) show broad spectrum antifungal properties. The maturation of the gastrointestin al cells was enhanced by cyclo(Phe-Pro), cyclo(Tyr-Pro), cyclo(Trp-Trp) and cyclo(Trp-Pro). The activity of these cyclic dipeptides thus indicates pot ential application of these compounds as pharmacological agents.