Ethanolic Walnut Kernel Phenolic Compounds and its Antimicrobial Effect

Introduction: Food-borne pathogens are causes of poisoning and gastrointestinal infections. In recent years, it is recommended to use natural materials like plant extracts and essences instead of chemical preservatives in food industry. Therefore, the aim of this study was to identify the phenolic compounds of ethanolic walnut kernel and its antimicrobial effect on some food-borne pathogens. Methods: In this experimental study, after collection of walnut kernel, its ethanolic extract was prepared. Then its antimicrobial activity on salmonella typhimurium, shigella disentriae, listeria monocytogenes was examined as Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) using microdilution method. Chloramphenicol (30µg) was used as the reference antimicrobial agent. Total phenols, flavonoids and flavonols were also determined by colorimetric method. Results: The results showed that MIC was between 0.625 and 1.25 mg/ml and MBC was between 1.25 and 2.5mg/ml for ethanolic extract. Total phenols were 365±14.71mg/g gallic acid equivalent, and total flavonoids and flavonols were 285±12.25 and 132± 1.63mg/g rutin equivalent, respectively. Conclusion: These findings showed that walnut kernel has antibacterial effects on three aforementioned bacteria and can substitute for chemical preservatives. More studies, such as examinations in food models are needed to unravel the antimicrobial effects of this plant.