Abstract
Medicinal plants continue to gain popularity on a global scale. Besides, there is a need for discovering new antibacterial natural extracts that could be used as antibiotics alternatives against resistant bacteria. In this respect, the aim of this study was to determine the phytochemicals, antioxidant activity, calorific nutritional value and antibacterial potential of four traditionally used wild medicinal plants (Achillea fragrantissima (Delile) Hayne, Teucrium polium L., Peganum harmala L. and Solenostemma argel (Forssk.) Sch. Bip. grow in Saint Catherine Protectorate, South Sinai, Egypt.
Standard methods were applied to determine the proximate composition, calorific nutritional value, secondary metabolites (phenolics and flavonoids), antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH·), ferrous ion chelating (FIC), 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS+) and Ferric reducing antioxidant power (FRAP) techniques in addition to the antibacterial potential of the active aqueous extracts by broth dilution technique.
The results obtained illustrated that T. polium recorded the highest nutritional calorific value (205.63 ± 5.76 calories/100 g dried plant), total phenolics (8.057 ± 0.322 g gallic acid equivalent/100 g dried plant), total flavonoids (2.013 ± 0.034 g catechin equivalent/ 100 g dried plant and antioxidant scavenging activity using DPPH (EC50 = 1.84 mg extract/g DPPH), FIC (IC50 = 0.068 mg extract/ml), ABTS (61.11%) and FRAP (2185.71 mmol Fe (II)/g extract) assays followed descendingly by A. fragrantissima, S. argel and P. harmala, respectively. There was direct relation between the flavonoids/ phenolics ratios and the radical scavenging activity among all extracts. Regarding the antibacterial potential, the extracts expressed broader antibacterial spectrum against Bacillus cereus(ATCC®11778™), Bacillus subtilis (ATCC®19659™), Escherichia coli (ATCC®10536™), klebsiella pneumoniae (ATCC®10031™), Listeria innocua (ATCC®33090™), Listeria monocytogenes (ATCC®19115™), Pseudomonas aeruginosa (ATCC®9027™), salmonella enterica (ATCC®15479™) and Salmonella typhimurium)ATCC®14028™(strains. The minimal inhibitory concentrations of the extracts estimated using broth dilution assay ranged from 0.049 to 1.56 mg/ml. T. polium extract possessed the highest activity among all other extracts.
In conclusion, the studied medicinal plants could be used as nutritional supplements, antioxidants and antibacterial botanicals for combating some of the pathogenic bacteria.