Antimicrobial effects of three herbs ( Brassica juncea , Forsythia suspensa , and Inula britannica ) on membrane permeability and apoptosis in Salmonella

This study aimed synergistic effects of three herbs in Salmonella via increased membrane permeability and apoptosis. Using high‐performance liquid chromatography, four types of phenylethyl glycosides and a lignan were detected in the herb mixture (Brassica juncea, Forsythia suspensa, and Inula britannica). During treatment with the herb mixture (1×, 2×, or 4× the MIC), viable cells decreased to 1·87 log CFU per ml (Salmonella Gallinarum) and 2·33 log CFU per ml (Salmonella Enteritidis) after 12 h of incubation according to inhibition of tricarboxylic acid cycle (P < 0·01). In addition, N‐phenyl‐1‐naphthylamine uptake increased from 229·00 to 249·67 AU in S. Gallinarum and from 232·00 to 250·67 AU in S. Enteritidis (P < 0·05), whereas membrane potential decreased from 8855·00 to 3763·25 AU and from 8703·67 to 4300·38 AU, respectively. Apoptotic Salmonella cells were observed by confocal laser scanning microscopy and flow cytometry. Transmission electron microscopy observations with negative staining showed protein leakage from damaged Salmonella. These results showed the synergistic effect of the three herbs against avian pathogenic Salmonella induced by membrane damage and apoptosis. Salmonella causes enormous economic losses in the poultry industry. These results indicated that potency of natural antimicrobial agents due to apoptosis in Salmonella.