Variation of polyphenols in a germplasm collection of globe artichoke.

Globe artichoke, a crop native to the Mediterranean Basin, is rich in polyphenols whose health-promoting properties have been well documented in literature. Here, we reported the variation of polyphenol content and antioxidant activity in plant parts (floral stem, receptacle, inner and outer bracts) of 17 cultivars. Our objectives were also to evaluate the influence of harvest time (winter and spring) on total polyphenol content and to assess the polyphenol composition by HPLC in six cultivars not previously analysed. The total content and profile of polyphenols were significantly different amongst cultivars and plant parts. 'Tema 2000', 'Nobre' and 'Violetto di Sicilia clone 4/8' had the highest level of total polyphenol content, whilst 'Camerys' and 'Tempo' had the lowest. Polyphenols resulted more abundant in the floral stem and receptacle. These were, respectively, rich in caffeoylquinic acids and apigenin derivatives. Each cultivar preferentially accumulated polyphenols in specific plant parts and, hence,may have a specific end-use based on its polyphenol content. In this view, the high level of total polyphenols in the receptacles of 'Tema 2000', 'Opal' and 'Nobre' makes them more suitable for the fresh consumption, whereas the floral stems of 'Violetto di Sicilia clone 4/8', 'Nobre' and 'Tema 2000' are suggested for the exploitation as source of natural antioxidants. In addition, the cultivar-dependency of both polyphenol content and antioxidant activity of globe artichoke extracts led to foresee the possible manipulation by specific breeding and selection programmes in order to improve the health-beneficial properties of globe artichoke head. Our findings prove also the influence of harvest time on the polyphenol content and thus suggest giving specific consideration to the other factors (e.g. temperature and photoperiod) that may affect polyphenol biosynthesis and accumulation in globe artichoke plant.