Comparison of Phytochemical Composition, Free Radical Scavenging Activity, and Antimicrobial Activity of Selected Herbs Against Two Foodborne Pathogenic Bacteria

Abstract

Spices and herbs, owing to their natural benefits to human health, are gaining momentum as food preservatives in recent years. Due to their antioxidant activity, their extracts with bioactive principles form the basis of pharmaceutical and food processing applications. Two of such crops, mountain mint (Pycnanthemum virginianum) and red turmeric (Curcuma longa), were compared for their phytochemical composition, the antioxidant activity of methanolic extracts, and their antimicrobial activity against foodborne pathogenic bacteria, Listeria monocytogenes, Salmonella enteritidis in this study. Our results showed that the mountain mint had higher total phenolic content and total tannin content: 614.41±3.96 and 529.74±4.39 mg gallic acid equivalents/gram dry weight extract. In comparison, red turmeric had higher total flavonoid content: 1250.51±8.10 mg catechin equivalents/gram dry weight extract. A lower IC50 value (21.39±0.86 μg/mL) of red turmeric reflected its higher antioxidant activity. A lower concentration of methanolic extract of red turmeric rhizome was needed for both MIC (62.5 and 125 μg/mL) and MBC (125 and 250 μg/mL) assay against L. monocytogenes and S. enteritidis, respectively. In conclusion, these findings showed the red turmeric methanolic extract as a source of potential phytochemicals and antioxidants exhibited relative efficiency with antimicrobial activity against two common foodborne pathogens. The results have implications for use in processed food preservation and protection against food spoilage pathogens.