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Antimicrobial and antioxidant activity of the vegetative and reproductive organs of Robinia pseudoacacia

Marinas Ioana C. (University of Bucharest, Faculty of Biology, Microbiology Department, Bucharest, Romania)
Oprea Eliza (University of Bucharest, Faculty of Chemistry, Bucharest, Romania)
Geana Elisabeta-Irina (National R&D Institute for Cryogenics and Isotopic Technologies, ICIT Rm. Valcea, PO Raureni, Rm. Valcea, Romania)
Chifiriuc Carmen (University of Bucharest, Faculty of Biology, Microbiology Department, Bucharest, Romania)
Lazar Veronica (University of Bucharest, Faculty of Biology, Microbiology Department, Bucharest, Romania)

The study was aimed to investigate antimicrobial and antioxidant activity of ethanol extracts obtain from leaves, seeds and sheaths of R. pseudoacacia. Total phenolic content (TPC, Folin-Ciocalteu method), antioxidant activity (TEAC assay) and antimicrobial activity (agar disk diffusion method and broth dilution method) of vegetative and reproductive organs of R. pseudoacacia were done. The highest content of polyphenols (expressed as gallic acid equivalents, GAE) obtained for R. pseudoacacia leaves extract (266.7 μg GAE mL-1 extract) followed by seeds extract (232.2 μg GAE mL-1 extract). The HPLC analysis showed presence of catechin (0.925 μg mL-1), rutin (0.831 μg mL-1), resveratrol (0.664 μg mL-1) and quercetin (0.456 μg mL-1) in leaves and catechin (0.127 μg mL-1), epicatechin (0.239 μg mL-1) and rutin (0.231 μg mL-1) in seeds extract. The results showed that the studied extracts exhibited a selective antimicrobial effect directed against Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Pseudomonas aeruginosa, Klebsiella pneumonie and Escherichia coli) bacterial strains. The combination leaves extract / antibiotic had the highest synergistic effect when compared to seeds and sheaths extracts. The same extract with penicillin, kanamycin and rifampin had highest synergetic effect against methicillin resistant S. aureus strain (MRSA), a strain which it has gained a great interest of microbiologists within past decades. The chemical characterization of ethanol extracts from the vegetative and reproductive organs of Robinia pseudoacacia, synergistic effects of certain antibiotics and acacia extracts, potential to increase antimicrobial activity of some commercial antibiotics against MRSA were done for the first time.

Keywords: antimicrobial activity, antioxidant activity, Robinia pseudoacacia, antibiotics