Extratos etanólicos de própolis obtidos a partir de diferentes concentrações de própolis e com álcool hidratado com diferentes teores de álcool/água foram analisados. A ação antioxidante destes extratos foi determinada através da captura do radical livre 1,1-difenil-2-picril-hidrazila (DPPH•) e do poder de redução férrico (FRAP) utilizando o complexo férrico-tripiridiltriazina (Fe 3+ -TPTZ). O teor de compostos fenólicos totais e a quantificação de flavonóides também foram verificados e obtidos por espectrometria de massas com ionização por electrospray (ESI(-)-MS) dos extratos. Observou-se que a composição química dos extratos de própolis e sua atividade antioxidante variam com a concentração de própolis e, principalmente, com o teor de álcool/água do etanol hidratado utilizado na extração. Foi possível perceber também que a atividade antioxidante dos extratos é significativamente dependente destes parâmetros de extração e que as composições de compostos fenólicos e flavonóides também variam muito. Os valores de FRAP não apresentaram, porém, boa correlação com o teor de flavonóides.Ethanolic extracts of propolis obtained with different concentrations of propolis and made using hydrous ethanol with various water/ethanol contents were analyzed. The antioxidant action of the extracts was determined by free radical 1,1-diphenyl-2-picryl-hydrazyl (DPPH•) scavenging and by ferric reducing ability power (FRAP), using the ferric-tripyridyl triazine (Fe 3+ -TPTZ) complex. The total phenolic and flavonoid contents were also determined, and the electrospray ionization mass spectrometry spectra (ESI(-)-MS) of the extracts were acquired. The chemical composition of propolis extracts and their antioxidant activity were observed to vary with the concentration of propolis, and especially with the water/ethanol contents of the hydrous ethanol used for extraction. The antioxidant activity of the extracts was also found to be significantly dependent on these extraction parameters, as well as on the composition of the phenolic compounds and flavonoids. FRAP values showed, however, poor correlation with the flavonoid content. Keywords: total phenolic contents, antioxidant activity, ESI(-)-MS fingerprint, propolis extraction, flavonoids IntroductionPropolis is a resin produced by honey bees by mixing wax, pollen, salivary secretions and collected natural resins. 1 The chemical composition of propolis is complex and varies with the vegetation visited by bees, as well as with bee species. [2][3][4][5][6] As propolis has characteristics that are beneficial to human health, such as antioxidant, anti-inflammatory, antifungal and anticancer activities, its chemical composition and properties have been extensively studied. [7][8][9][10] The antioxidant activity of ethanolic extracts of propolis has been evaluated by free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH • ) scavenging, 8 by the ferric reducing ability power (FRAP) using the ferric-tripyridyltriazine Antioxidant Activity and Composition of Propolis Obtained by Different Methods o...
Foram comparados os resultados de determinações quantitativas de ésteres metilícos de ácidos graxos de óleos vegetais (soja, linhaça e dendê) entre oito métodos de esterificação com catálises ácidas e básicas. Os métodos selecionados foram descritos por Metcalfe, 1966 (MET, ref. 17); Bannon, 1982 (BAN, ref. 18); Joseph e Ackman, 1992 (JAC, ref. 3); Hartman e Lago, 1973 (HLA, ref. 19); Jham, 1982 (JHA, ref. 20); ISO 5509, 1978 (ISO, ref. 21); Bannon, 1982 (BBA, ref. 15) e Schuchardt e Lopes, 1988 (SLO, ref. 22). Apesar da grande variação apresentada para o teor de ácidos graxos insaturados, todos os métodos foram eficientes para os ácidos graxos saturados. Os resultados obtidos mostram que a determinação de ácidos graxos pode ser afetada pela composição do óleo e que os métodos JAC, ISO e BBA são os mais eficientes. Os métodos ISO e BBA por apresentarem baixa toxidez e baixo custo são os recomendados para amostras que apresentem baixa acidez. O método JAC deve somente ser recomendado para amostras com alta acidez porque os métodos ISO e BBA são realizados em meio básico e podem não determinar os ácidos graxos livres.The results of the quantitative determination of fatty acid methyl esters of vegetable oils, (soybean, flaxseed, and palm oils) by eight basic and acid catalysis esterification methods were compared. The selected methods were described by Metcalfe, 1966 (MET, ref. 17 Schuchardt and Lopes, 1988 (SLO, ref. 22). Despite the large variation in the determination of unsaturated fatty acids, all the methods were efficient in the analysis of saturated fatty acids. The results obtained show that fatty acid analysis may be affected by oil composition and that JAC, ISO, and BBA methods are more efficient. ISO, and BBA are recommended for low acidity samples due to their low reagent toxicity and cost. The JAC method is recommended only for high acidity samples, as the ISO and BBA methods are carried out in basic medium and cannot analyze the free fatty acids.
There is a mounting concern about the intake of foods containing trans fatty acids (TFA) due to their deleterious effects on human health, mainly on the cardiovascular system. In this way, it is important to consider the processes that form TFA in foods, and the alternatives to minimize them. Among the processes that result in the formation of TFA, the hydrogenation of vegetable oils stands out for its impact on the diet of people living in industrialized countries. Other processes such as edible oil refi ning, meat irradiation, food frying, and biohydrogenation also contribute to increase the daily intake of TFA.
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