ABSTRACT
The appearance of resistant bacteria was found to reduce the efficiency of antimicrobial therapies with the current antibiotics, thereby increasing the need for more efficient drugs for the treatment of infections. Several studies have demonstrated an increase in antimicrobial activity following the interaction of several compounds with metal ions. The present study used a methodology adapted for antimicrobial bioassays using plant extracts, in compliance with the standards of the Clinical and Laboratory Standards Institute against Gram-positive and Gram-negative bacteria. The results obtained were considered appropriate for determining MIC, MBC as for performing antimicrobial sensitivity testing with good efficiency and reproducibility. The bacteria Pseudomonas fluorescens exhibited high sensitivity to the tested compounds, being efficient to evaluate the antibacterial activity. The bioassays with the metal complexes of flavonoid quercetin and Ga(III) ions, and synthetic ligand H2bbppd and Cu(II) ions showed a greater inhibitory effect than their individual ligands, thus, the addition indicated an increase in the antimicrobial activity after the coordination. Both metal complexes exhibit good antimicrobial performances, such as low minimum inhibitory concentration (MIC ≤ 250 µg/ml), bactericidal effect and a broad activity spectrum, which qualify these compounds as suitable candidates to the next step of drugs fabrication. Nevertheless, further studies on the mechanism of growth inhibition and toxicity are needed, in order to evaluate the potential of therapeutic application.
ABSTRACT
The objective of this study was to determine the damage levels caused by Orthezia praelonga Douglas, 1891 and Leucoptera coffeella (Guérin-Mèneville 1842), on rangpur lime and Obatã coffee leaves, respectively. Measurements were based on a new concept for the evaluation of the following plant physiological parameters: photosynthesis, stomatal conductance, leaf temperature and transpiration, and internal concentration of CO2 (by infrared analyzer). A negative correlation between infestation level and photosynthesis was found, where the negative inflexion point of the curve was considered as a reference for damage levels. The control level for O. praelonga is below the 7-13 percent limit for damaged leaf area (40 to 70 scales per leaf), while for L. coffeella it is below the 26-36 percent limit for the same variable. Photosynthesis provided the best correlation for this type of analysis.
O objetivo deste trabalho foi estabelecer, baseado em um novo conceito de avaliação de parâmetros fisiológicos vegetais, o nível de dano causado por Orthezia praelonga Douglas 1891 e por Leucoptera coffeella (Guérin-Mèneville 1842) em folhas de limão cravo e cafeeiro 'Obatã', respectivamente. Foram feitas leituras de trocas gasosas por infravermelho, além da avaliação da condutância estomática, temperatura foliar, transpiração foliar e concentração interna de CO2. Os dados demonstraram uma correlação negativa entre o nível de infestação e a fotossíntese, sendo o ponto de inflexão negativa da curva tomado como referência de nível de dano, onde o nível de controle para O. praelonga encontra-se abaixo do limite de 7 a 13 por cento de área foliar lesionada (40 a 70 cochonilhas por folha), e o de L. coffeella encontra-se abaixo dos valores de 26 a 36 por cento de área foliar lesionada. Dentre os parâmetros avaliados a fotossíntese foi o que demonstrou melhor correlação para este tipo de análise.