Browsing by Author "Pedro, Ana"
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- Effect of drying on the phenolic content and antioxidant activity of thistle flowerPublication . Pedro, Ana; Barracosa, Paulo; Guiné, Raquel; Gonçalves, FernandoThe thistle is a plant that is associated with the production of cheese, as it is responsible for the phenomenon of coagulation of milk. Lately there has been an increased the number of studies about this plant, related to the chemical composition in order to perceive the benefits for human health. The aim of this study was to characterize the thistle flower in relation to its composition in phenolic compounds and also evaluate its antioxidant activity. For that, were studied samples of thistle flower from species Cynara cardunculus L. after freeze-drying and convective drying at different temperatures (40 ºC, 50 ºC and 60 ºC). After each treatment were made from each sample two successive extractions with solutions of methanol (98% v/v) and acetone (60% v/v). The extracts were then used for characterization of the samples in phenolic compounds and determination of antioxidant activity. The results showed that the amount of phenolics and antioxidant activity in the flower thistle varies depending on the drying temperature decrease occurring as they use higher drying temperatures.
- Evaluation of phenolic compounds composition, antioxidant activity and bioavailability of phenols in dried thistle flowerPublication . Guiné, Raquel; Pedro, Ana; Matos, Joana; Barracosa, Paulo; Nunes, Cláudia; Gonçalves, FernandoThe objective of this work was to characterize the thistle flower in relation to the composition of phenolic compounds and antioxidant activity, as well as the evalua- tion of the stability of the phenols along the digestive tract. In addition, the effect of drying temperature was evaluated and the composition in polysaccharides was also studied. For this, samples of thistle flower were lyophilized and dried at 40, 50 and 60 C. Methanol:acetic acid (98:2 v/v) and ace- tone:water (60:40 v/v) extracts were obtained and analysed for antioxidant activity, phenolic compounds, ortho-diphe- nols, flavonoids, phenolic acids and polysaccharides, using colorimetric methods, HPLC and GC-FID. The results showed that the phenolic compounds and antioxidant activity with ABTS or DPPH methods on thistle flower decreased by 20, 34 and 72 %, respectively, with increasing temperature from 40 to 60 C. The amount of compounds available for intestinal absorption decreased along the gas- trointestinal system, by 15–50 %. The presence of sugars constituent of pectic polysaccharides was observed (101.6–222.0 mg/g) as well as of hydroxybenzoic (0.19–1.26 mg/g) and hydroxycinnamic acids (1.57–5.59 mg/g). As a conclusion it was found that thistle flower is rich in bioactive compounds with potential importance for the human health.
- Evaluation of phenolic compounds, antioxidante activity and bioavailability in dried thistle flowerPublication . Guiné, Raquel; Pedro, Ana; Barracosa, Paulo; Gonçalves, FernandoThe thistle flower is usually associated to the making of cheese, because it’s responsible for the phenomenon of the coagulation of milk. However, the number of studies about the chemical composition on this plant has risen, in an attempt to understand its health benefits. The objective of this work was to characterize the thistle flower in relation to its antioxidant activity, the composition of phenolic compounds and evaluate its stability along the digestive tract. To achieve these goals, samples of thistle flower of the species C. Cardunculus spp flavescens were analysed after lyophilization and oven drying with forced convection at different temperatures (40, 50 and 60 ºC). After each treatment two successive extractions with solutions of methanol (98% v/v) and acetone (60% v/v) were carried out. The extracts obtained were then used to quantify the levels of total phenolic compounds, ortho-diphenols and flavonoids. The antioxidant activity was determined using both the DPPH and ABTS methods. The evaluation of the bioavailability of the compounds present was evaluated by subjecting the various extracts to conditions simulating the digestive tract. Through the analysis of the results it was found that the amount of phenolic compounds and antioxidant activity on thistle flower varied depending on the drying temperature, increasing their degradation as the temperature was raised. The results for bioavailability showed a decrease in the amounts of compounds available for intestinal absorption.