Evaluation of phenylpropanoids in ten Capsicum annuum L. varieties and their inhibitory effects on Listeria monocytogenes murray, webb and Swann Scott a

Extracts of pepper from ten different varieties of Capsicum annuum L. were prepared and their phenylpropanoids content was analysed by HPLC. There were seven different compounds identified at varying concentrations depending on pepper variety (L-phenylalanine, t-cinnamic acid, o-coumaric acid, m-coumaric acid, ferulic acid, caffeic acid and capsaicin) which are intermediates of the capsaicinoids pathway. The inhibitory action of the pepper extracts was evaluated against Listeria monocytogenes Murray, Webb and Swann Scott A by the agar diffusion test. Results showed that three of the 10 extracts had an antibacterial effect. Guajillo San Luis pepper presented the highest inhibitory effect, and contained the major concentration of cinnamic and caffeic acids. In order to analyse the individual contribution of every phenylpropanoid to the bacteriostatic effect, different concentrations were tested on the growth and survival of L. monocytogenes Swann Scott A. There were no significant differences (p>0.05) in the t-cinnamic, o-coumaric, m-coumaric, ferulic acids and capsaicin among the samples. However, a significant difference was found between these compounds and the bactericidal action of caffeic acid. The results confirmed that L. monocytogenes Swann Scott A is inhibited by some pepper extracts, and also that some specific phenylpropanoids had a bacteriostatic effect.