Optimization of ß-cyclodextrin-based extraction of antioxidant and anti-browning activities from thyme leaves by response surface methodology.

Thyme (Thymus vulgaris) has been demonstrated to extend the shelf-life of food products, being also a potential source of bioactive compounds. The aim of this research was to optimize the ultrasound assisted extraction employing ß-cyclodextrin aqueous solutions as no-contaminant technology and Response Surface Methodology to obtain thyme extracts with the maximum antioxidant capacity. The optimal extraction conditions were: a solution of ß-ciclodextrin 15 mM, an ultrasonic treatment time of 5.9 min at a temperature of 36.6 °C. They resulted in an extract with a polyphenolic content of 189.3 mg GAE/mL, an antioxidant activity (DPPH) of 14.8 mg GAE/mL, and ferric reducing/antioxidant power (FRAP) of 3.3 mg GAE/mL. Interestingly, the extract demonstrated to inhibit the production of Maillard browning products and can be considered a potential antiglycant agent. The obtained data is important for developing eco-friendly technologies in order to obtain natural antioxidant extracts with a potential inhibitory capacity of Maillard glycation reaction.

Antioxidant activity and physicochemical characteristics of honeys from the eastern Amazon region, Brazil / Atividade antioxidante e características físico-químicas de méis da Amazônia Oriental, Brasil / Antioxidant activity and physicochemical characteristics of honeys from the eastern Amazon region, Brazil

RESUMO O mel é um produto natural que apresenta várias propriedades benéficas para a saúde, tais como atividade antinflamatória, antioxidante e antimicrobiana, as quais dependem de sua composição. Neste contexto, as propriedades físico-químicas (cor, pH, conteúdo de cinzas, umidade, açúcares e compostos fenólicos totais) e a atividade antioxidadente (capacidade de remoção do radical DPPH) de méis de abelhas Apis mellifera de Santarém, na principal região de produção de mel na Amazônia Oriental, Brasil, foram avaliadas. A maioria das amostras teve cor escura e apresentaram-se ácidas. Os teores de cinzas e a umidade variaram de 0,112 a 0,318 e de 14,751 a 17,514, respectivamente. O teor de açúcares redutores vairou entre 62,873 e 91,563%. O teor total de compostos fenólicos foi mais elevado que os já reportados na literatura, variando entre 15,22 e 16,51 mg g−1 e 17,70 e 18,94 mg g−1 para amostras de mel protegidas e expostas à radiação UV, respectivamente. A quercetina foi encontrada apenas no mel que foi protegido da luz, com teores variando entre 0,24 e 0,43 mg g−1. A ausência de quercetina nas amostras de mel expostas à luz sugere que a radiação UV pode ter degradado esse composto. Todas as amostras apresentaram máxima capacidade de remover o radical DPPH próxima a 50%. Houve correlação inversa entre a cor e o pH, cinzas, açúcares redutores e teor de umidade, e correlação positiva entre a cor e o teor de composto fenólicos e a atividade antioxidante.

ABSTRACT Honey is a natural product that has several beneficial properties for health, such as anti-inflammatory, antioxidant and antimicrobial activities, which depend on its composition. In this context, physicochemical properties (colour, pH, ash, moisture, sugars, and total phenolic contents) and antioxidant activity (DPPH radical scavenging ability) of Apis mellifera honeys from Santarém, the main honey production area in the eastern Amazon region, were evaluated. Most samples were dark in colour and acidic. The ash and moisture contents ranged from 0.112 to 0.318 and from 14.751 to 17.514, respectively. The reducing sugars content was 62.873-91.563%. The total amount of phenolic compounds was higher than normally reported, ranging between 15.22 and 16.51 mg g−1 and 17.70 and 18.94 mg g−1, for honey after and before exposure to light, respectively. Quercetin was found only in honey that had been protected from light, with values ranging from 0.24 to 0.43 mg g-1. The absence of quercetin in the samples of honey exposed to light suggests that UV radiation has degraded this compound. All samples presented maximum radical scavenging capacity close to 50%. Our results showed inverse correlations between the colour and pH, ash, reducing sugars, and moisture content, and positive correlations between the colour and the concentration of phenolic compounds, and antioxidant activity.

Functionalization of chitosan by a free radical reaction: Characterization, antioxidant and antibacterial potential.

Chitosan was functionalized with epigallocatechin gallate (EGCG) by a free radical-induced grafting procedure, which was carried out by a redox pair (ascorbic acid/hydrogen peroxide) as the radical initiator. The successful preparation of EGCG grafted-chitosan was verified by spectroscopic (UV, FTIR and XPS) and thermal (DSC and TGA) analyses. The degree of grafting of phenolic compounds onto the chitosan was determined by the Folin-Ciocalteu procedure. Additionally, the biological activities (antioxidant and antibacterial) of pure EGCG, blank chitosan and EGCG grafted-chitosan were evaluated. The spectroscopic and thermal results indicate chitosan functionalization with EGCG; the EGCG content was 25.8mg/g of EGCG grafted-chitosan. The antibacterial activity of the EGCG grafted-chitosan was increased compared to pure EGCG or blank chitosan against S. aureus and Pseudomonas sp. (p<0.05). Additionally, EGCG grafted-chitosan showed higher antioxidant activity than blank chitosan. These results indicate that EGCG grafted-chitosan might be useful in active food packaging.

Antioxidant activity of anthocyanins from quixabeira (Sideroxylon obtusifolium) fruits / Atividade antioxidante de antocianinas de frutos de quixabeira (Sideroxylon obtusifolium)

ABSTRACT The fruits of Sideroxylon obtusifolium T.D. Penn. are small berries which have dark purple skin color at maturity due the anthocyanins presence. Therefore, the aim of this research was to evaluate the antioxidant activity of anthocyanins from mature fruits which were obtained at a semi-arid region of Paraiba/BR. In addition, the total anthocyanins content was measured by the pH differential method. The anthocyanins were purified by solid-phase extraction (SPE) using C18 Sep-Pak cartridges and submitted to antioxidant activity determined by scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH·). The butylated hydroxytoluene (BHT) was the positive control and the results were expressed as DPPH· scavenging activity (%). Anthocyanins content were higher in the husks (236.15 mg cyanidin-3-glucoside 100g-1 fw) than in the pulp (30.49 mg cyanidin-3-glucoside 100g-1 fw). The results showed that the potential free radical scavenging grew with the increase of concentration used and the reaction time. The ability of the anthocyanins in scavenging the free radical was statistically greater than the BHT one. The anthocyanins which were present in this fruit may supply substantial dietary source of antioxidant that may promote health and produce disease prevention effects or that could be applied in food industry as a good source of natural pigments.

RESUMO Os frutos da Sideroxylon obtusifolium TD Penn., são bagas pequenas que, quando maduras, apresentam a coloração roxo-escuro devido à presença de antocianinas. Assim, o objetivo desta pesquisa foi avaliar a atividade antioxidante das antocianinas desses frutos maduros obtidos da região do semiárido da Paraíba/BR. Além disso, o teor de antocianinas total foi quantificado pelo método de pH diferencial. As antocianinas foram purificadas por extração em fase sólida (EFS) utilizando cartuchos Sep-Pak C18 e submetidas à avaliação da atividade antioxidante por meio da capacidade de sequestrar o radical DPPH·. Butil-hidroxi-tolueno (BHT) foi utilizado como controle positivo e os resultados foram expressos como percentual de sequestro de radical livre. Os resultados demonstraram que o teor de antocianinas presente nas cascas foi maior (236,15 mg de cianidina-3-glicosídeo 100g- 1, peso fresco) do que na polpa (30,49 mg de cianidina-3-glicosídeo 100g-1, peso fresco) e que o percentual de sequestro de radical livre aumentou com o aumento da concentração utilizada e o tempo de reação. A habilidade das antocianinas em sequestrar o radical livre foi estatisticamente superior à do BHT. As antocianinas presentes nesta fruta podem fornecer fonte dietética significativa de antioxidantes que podem promover a saúde e produzir efeitos de prevenção de doenças ou ser aplicada na indústria de alimentos como uma boa fonte de pigmentos naturais.

Atividades antioxidante e antimicrobiana dos extratos de própolis e açaí (Euterpe oleracea mart) / Antioxidant and antimicrobial activities of propolis and açai (Euterpe oleracea Mart) extracts

A própolis é uma resina natural que apresenta diversas ações biológicas devido a presença de fenólicos, especialmente flavonóides, em sua composição. O fruto do açaí (Euterpe oleracea Mart) é fonte de antocianinas, que também pertencem ao grupo dos flavonóides. O objetivo deste estudo foi avaliar o efeito antioxidante e antimicrobiano dos extratos de açaí e propolis em associação. A atividade antimicrobiana foi avaliada por ensaio em caldo enriquecido e a atividade antioxidante foi avaliada pelo método do sequestro de radicais DPPH. Os resultados mostraram que o extrato de própolis em pequenas concentrações apresentou atividade sobre o crescimento de S. aureus e S. epidermidis, e que ambos os extratos apresentaram atividade antioxidante. Foi possível concluir que ocorreu sinergismo entre os extratos de própolis e de açaí em relação à atividade antioxidante, bem como esta associação poderá apresentar atividade antimicrobiana caso o extrato de própolis seja utilizado em quantidade suficiente na formulação. Assim, esses extratos podem ser usados em formulações para uso tópico para prevenir o envelhecimento da pele e, possivelmente, transtornos causados pelos microrganismos empregados no estudo.

Propolis is a natural resin, collected mainly by the honey bee, Apis mellifera, which has been shown to have many biological roles, including antioxidant and antimicrobial effects, both conferred by phenolic compounds, especially flavonoids. The fruit of the açai palm is an important source of anthocyanins, which are also phenolics of the flavonoid group. The aim of this study was to assess the antioxidant and antimicrobial effects of a mixture of propolis and açai extracts. Antimicrobial activity was assessed by BHI broth culture with diluted extract, followed by agar subculture, while antioxidant activity was assessed by the DPPH radical scavenging assay. The results showed that around 2% of the propolis extract showed antimicrobial activity against Staphylococcus aureus and S. epidermidis, while low concentrations of both the ethanolic propolis and aqueous açai extracts, alone and combined, exhibited antioxidant activity. In conclusion, this study showed that the antioxidant effects of propolis and açai were summed in the mixed extracts. Furthermore, this combination would show antimicrobial activity if the minimum inhibitory concentration of propolis extract established in this study were used in the formulation. Hence, these extracts could be mixed into formulations used topically to prevent skin aging and, possibly, disorders caused by microbes, such as acne.