ANTIOXIDANT AND ANTIBACTERIAL ACTIVITIES OF SOME NATURAL POLYPHENOLS

The present study provides information on separation and identification of natural bioactive compounds from different vegetal materials with potential applications as antibacterials and plant growth modulators. Natural extracts were obtained by alcoholic and water extraction from spruce bark, grape seeds, Crataegus monogyna (hawthorn) and Asclepias syriaca (milkweed). HPLC-DAD analysis revealed that gallic acid (12.54 mg/100 g) and catechin (85.52 mg/100 g) were the most abundant compounds in hawthorn and grape seed extracts, vanillic acid (71.9 mg/100 g) was found in high concentrations in spruce bark wood, while milkweed extracts were characterized by the presence of hydroxycinnamic acids and flavonoids. The DPPH assay indicated that the highest radical scavenging activity was registered by grape seeds (EC50 = 45.75 mu g) and hawthorn (EC50= 17.8 mu g) alcoholic extracts. The same extracts exhibited antibacterial properties on Staphylococcus aureus, while the samples obtained from spruce bark and milkweed extracts inhibited the development of Escherichia coli and Pseudomonas aeruginosa species. Furthermore, the toxicity of the natural extracts was evaluated by their application in germination tests of Phaseolus vulgaris. The obtained results demonstrated that a:high concentration of polyphenols has an inhibitory effect on plant development, while lower concentrations determine a considerable stimulation of plantlet elongation.