Antioxidant analysis of flavonoids extracted from Artemisia argyi leaf and their antibacterial activities against food-borne pathogens Escherichia coli and Staphylococcus aureus

Plant-derived flavonoids have excellent bioactivities and applications, especially those from herbs, and it is hypothesized that flavonoids also play an important role in the functions of edible and medicinal Artemisia argyi. Therefore, in the present work, the component and structure of A. argyi leaf flavonoids (AALFs) were characterized, and their antioxidant and antibacterial activities were further investigated. Component determination results showed that the contents of flavonoids, carbohydrates, proteins, polyphenols in AALFs were 90.03 ± 1.37%, 1.24 ± 1.58%, 1.89 ± 1.42% and 6.84 ± 1.13%, respectively. The typical structural units of flavonoids in AALFs were analyzed and verified by ultraviolet visible (UV-VIS) spectroscopy, fourier transform infrared (FT-IR) spectroscopy and Nuclear magnetic resonance (NMR) detection. In vitro antioxidant analysis indicated that AALFs had excellent scavenging effects on 1,1-diphenyl-2-picrylhydrazyl (DPPH); ABTS, 2,2′ -azinobis-di-(3-ethyl-benzothiazolin-6-sulfonic acid) diammonium salt (ABTS), hydroxyl and superoxide radicals, and the corresponding 50% inhibitory concentration (IC₅₀) values were 0.176 mg/mL, 0.538 mg/mL, 0.236 mg/mL and 0.192 mg/mL. Meanwhile, disk diffusion assay showed that AALFs could efficiently inhibit the growth profiles of Escherichia coli and Staphylococcus aureus, and the minimum inhibitory concentrations (MICs) were 0.8 mg/mL and 0.65 mg/mL. Results of this work will provide help for utilization of A. argyi leaf and its flavonoids as preservatives to avoid food deterioration and food-borne pathogen spoilage.