Evaluation of allelopathic potential, antimicrobial and antioxidant activities of Pyrostegia venusta (Ker Gawl.) Miers (Bignoniaceae) leaf organic extracts

Abstract

This paper presents the results of allelopathic, antimicrobial and antioxidant activities of organic extracts (hexane, ethyl acetate and methanol) from the leaves of Pyrostegia venusta (Ker Gawl.) Miers (Bignoniaceae). Allelopathic activity was assessed based on Cucumis sativus (cucumber) development for the parameters main root length, number of secondary roots and hypocotyl length. All tested extracts affected the first two parameters, while the hypocotyl length was not affected only by the ethyl acetate extract. For antimicrobial activity, assessed by MIC assay, hexane extract showed moderate inhibition for Staphylococcus aureus (0.9 mg mL-1) and strong inhibition for Enterococcus hirae (0.5 mg mL-1). Ethyl acetate extract showed strong activity against Candida albicans (0.3 mg mL-1), whereas methanolic extract was not active against the tested microorganisms. On the other hand, methanol extract showed the most promising radical scavenging capacity (Effective Concentration 50% - EC50 = 102.0 ± 56.9 mg mL-1, with TEC50 = 30 min) in DPPH assay (2,2-diphenyl-1-picryl-hidrazil) and the highest level of phenolic compounds (116.2 ± 83.0 mg acid garlic g sample-1), as indicated by Folin-Ciocalteau assay.