Antioxidant properties and antibacterial activity of water extracts from Sambucus nigra L. under different conditions

Abstract

In folk medicine, dried white flowers of Sambucus nigra L. are used to make infusions, decoctions, and juices. The present article aims to study and compare the antioxidant activity of aqueous solutions of leaves and flowers of Sambucus nigra L obtained at different exposure times and assess the antibacterial activity of these solutions against Escherichia coli ATCC 8739, Salmonella NCTC 6017, Listeria monocytogenes NCTC 11994, and Staphylococcus aureus ATCC 25093. We studied the physicochemical properties of aqueous extracts of leaves (fresh) and flowers (fresh and dry) of Sambucus nigra L collected from the Rhodope region of Bulgaria. The samples from Sambucus nigra L were analyzed to determine their total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP). The diameters (in millimeters) of the growth inhibition zones of four pathogens were measured, and a comparative assessment of their antibacterial activity was made. The infusions of fresh blossoms and fresh leaves of Sambucus nigra L had the highest antioxidant activity at the total contact time of 30 minutes (82.7mmol TE/100ml) and 35 minutes (36.5mmol TE/100ml), respectively. The phenol-richest infusions were those made from dried flowers of Sambucus nigra L after a 30-minute contact time (86.7mg GAE/ml). Of the four pathogens we studied, we found that the extracts affected partially only the pathogenic bacteria of Salmonella. The highest content of bioactive components was obtained from dried blossoms of Sambucus nigra L. for infusions with a total contact time of 30 minutes and for decoctions at a contact time of 45 minutes.