RESUMEN
Isobavachalcone (IBC) is a natural prenylated chalcone with a broad spectrum of pharmacological properties. In this work, we newly synthesized and investigated the antibacterial activity of IBC against Gram-positive, Gram-negative and mycobacterial species. IBC was active against Gram-positive bacteria, mainly against Methicillin-Susceptible Staphylococcus aureus (MSSA) and Methicillin-Resistant Staphylococcus aureus (MRSA), with minimum inhibitory concentration (MIC) values of 1.56 and 3.12 µg/mL, respectively. On the other hand, IBC was not able to act against Gram-negative species (MIC > 400 µg/mL). IBC displayed activity against mycobacterial species (MIC = 64 µg/mL), including Mycobacterium tuberculosis, Mycobacterium avium and Mycobacterium kansasii. IBC was able to inhibit more than 50% of MSSA and MRSA biofilm formation at 0.78 µg/mL. Its antibiofilm activity was similar to vancomycin, which was active at 0.74 µg/mL. In order to study the mechanism of the action by fluorescence microscopy, the propidium iodide (PI) and SYTO9 fluorophores indicated that IBC disrupted the membrane of Bacillus subtilis. Toxicity assays using human keratinocytes (HaCaT cell line) showed that IBC did not have the capacity to reduce the cell viability. These results suggested that IBC is a promising antibacterial agent with an elucidated mode of action and potential applications as an antibacterial drug and a medical device coating.
RESUMEN
Foods are subject to contamination by chemical substances, including aflatoxins, which are potentially carcinogens. The presence of these substances in food is important risk in human population and animals. The aim of this study was to determine the occurrence of aflatoxins B1, B2, G1 and G2 in samples of peanuts and paçoca ramdomly acquired in shops and food market in the city of Alfenas-MG, Brazil, from June 2006 to February 2007. The technique used for the separation, identification and quantification of the substances was a liquid-liquid extraction with subsequent thin layer chromatography (TLC). Results showed that 38 percent of peanuts samples and 13 percent of paçoca samples were contaminated with aflatoxins and the concentrations ranged from 21 to 138 μg kg-1. All positive samples exceeded the maximum level established by Brazilian Legislation (20 μg kg-1). The results obtained in this work confirm the need for frequent monitoring of the presence of aflatoxins in food.
Os alimentos estão sujeitos à contaminação por substâncias químicas, dentre elas as aflatoxinas, as quais são potencialmente carcinogênicas. A presença de tais substâncias nos alimentos constitui importante risco para a população tanto humana quanto animal. O objetivo deste estudo foi determinar a ocorrência de aflatoxinas B1, B2, G1 e G2 em amostras de amendoim e paçoca adquiridas aleatoriamente no comércio da cidade de Alfenas- MG, Brasil, no período de junho de 2006 a fevereiro de 2007. A técnica utilizada para a separação, identificação e quantificação das substâncias foi a cromatografia em camada delgada com prévia extração, líquido-líquido, dos analitos. Os resultados demonstraram que 38 por cento das amostras de amendoim e 13 por cento das amostras de paçoca estavam contaminadas com aflatoxinas, sendo que as concentrações variaram de 21 a 138 μg kg-1. Todas as amostras positivas excederam o limite máximo permitido, preconizado pela legislação brasileira de 20 μg kg-1. Os achados do presente estudo corroboram com os relatados na literatura e confirmam a necessidade do freqüente o nitoramento da presença de aflatoxinas em alimentos.
