Antioxidant and Antimicrobial Potential of Phenolic Metabolites from Traditionally Used Mediterranean Herbs and Spices

The phenolic extracts of fifteen Mediterranean medicinal plants, as well as their antioxidant and antimicrobial activities were investigated to grade their potential as additives in the food industry. Phenolic profiles of plant extracts were determined spectrophotometrically (total phenolics and phenolic subgroups) while individual compounds were identified using chromatographic assays. The biological activity of samples was determined using five antioxidant assays, while the antibacterial potential was determined against six foodborne pathogens (Camplyobacter coli, Escherichia coli, Salmonela Infantis, Bacillus cereus, Listeria monocytogenes, and Staphylococcus aureus). The results showed significant variations in phenolic profile of plants and consequently their biological activity. Bearberry contained the highest concentration of phenolics, was extremely rich in non-flavonoids and also had the highest amount of catechins that resulted with good reducing and free radical scavenging properties and low chelating activity. All extracts were not effective against tested microorganisms with Gram-positive bacteria being more sensitive (especially S. aureus). The most effective extracts were St. Johns wort against S. aureus with minimal inhibitory concentration (MIC) of 1.00 mg/mL), bay laurel and nettle against B. cereus (MICs of 1.67 mg/mL), and woodland strawberry against L. monocytogenes (MIC of 3.33 mg/mL).