ANTIOXIDANT ACTIVITY OF ARTICHOKE EXTRACTS AND BY-PRODUCTS

The aim of this work was to evaluate the antioxidant activity of single polyphenols or complex extracts from artichoke edible parts or industrial by-products. The present results are part of a larger project dealing with products from plants grown in Brittany (Western France) such as artichoke, buckwheat and cauliflower. Raw and enriched extracts were prepared from commercial artichoke hearts and by-products from a factory producing frozen artichoke hearts (bracts, fuzz, liquid effluents…). Raw extracts were obtained using a water - ethanol mixture. Enriched extracts were prepared from raw extracts through a liquid – liquid extraction procedure with ethyl-acetate. Liquid effluents were also studied after filtration. Chlorogenic acid, cynarin, narirutin, cynaroside, isorhoifolin and caffeic acid were analysed by HPLC. The main components of the extracts were chlorogenic acid, cynarin A and narirutin. The antioxidant activity of the enriched by-product extract, as measured with the oxygen radical absorbance capacity (ORAC) method, was in the range of 7000 micromoles of trolox equivalent per g, which is close to values observed for the best antioxidant natural extracts. The calculated ORAC values of the different extracts (as the sum of individual polyphenol contributions) are well correlated to the measured ORAC value (R^² = 0.9958). In all extracts, the main contribution to the ORAC value was brought by cynarin A. Pholasin method, a recent assay for the evaluation of the antioxidant activity, was also performed on the extracts and single polyphenols. A good correlation was observed with the ORAC value. This work showed that extracts with high antioxidant activity can be obtained from artichoke and artichoke industrial by-products. These extracts might be of interest within the developing market of nutritional ingredients.