Analysis of the 2-Phenylethyl isothiocyanate present in Brassica leaves and their potential application as antimicrobial agent against bacteria strains isolated from Human and Pig gastrointestinal tracts

摘要

This work aims to evaluate the effect of 2-Phenyethyl isothiocyanate (PEITC), a predominant isothiocyanate derived from glucosinolate named glucoranturtiin, particularly important in Brassica rapa (turnip-inflorescences, leaves, stems and roots) and Nasturtion officinalis (watercress), against pathogenic Gram-negative and Gram-positive bacteria, isolated from Human (clinical) and animal gastrointestinal segments. Also standard bacteria strains were sued in the study. Using a disc diffusion method, different doses of PEITC were tested. The compound was dissolved in dimethyl sulfoxide (DMSO) and tested at 5 different concentrations using a standard disk-diffusion assay (0.015, 0.15, 0.75, 1.50, and 3.00 μmoles). Positive (commercial standards antibiotic) and negative controls (DMSO only) were always included in the tests. All the experiments were conducted in triplicate. The antibacterial activity was also assessed by the application of the percentage of relative inhibition zone (%RIZD) in relation to the antimicrobial effect of commercial standard antibiotics. The results showed that, there were clear concentration differences (P < 0.05) with respect to the in vitro growth inhibition effects as well as differences in the sensitivities of the individual bacteria. The antimicrobial activity of PEITC was always a dose-dependent. The results also showed that antimicrobial activity of PEITC was higher in Gram-positive and lower in Gram-negative. Our results are useful and suggest that PEITC might be useful in controlling Human and animal pathogenic bacteria's growth and therefore could be considered as alternative to, or in combination with, the current antibiotic-based controls used for treating pathogenic bacteria. However, further studies are needed to determine their MIC values, to evaluate their commercial and economical effectiveness, the eventual synergistic effects with others compounds, as found in the consumption of the Brassica foods; toxicity bioassays must as well be performed.