Evaluation of phenolic compounds composition, antioxidant activity and bioavailability of phenols in dried thistle flower

The 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.