Phenolic compounds, antioxidant activity and lignin content of 'Spinoso sardo' globe artichoke grown under different photoperiods

Globe artichoke (Cynara cardunculus L. var. scolymus Fiori) is a rich source of phenolic compounds with health promoting properties. In plants, the concentration of polyphenolic compounds depends on environmental factors like temperature, photoperiod or availability of nutrients. In this work we studied, on artichoke heads, the effect three photoperiodic conditions (length of the light periods: natural day length (control); 15 and 17 h) on the concentration of total phenol, flavonoids, lignin and on the antioxidant activity. On artichoke heads, the rise of the day length caused a significant decrease of total phenols concentration. On control plants, the total phenolic content exceeded by about 25 and 37% that of photoperiod extended to 17 and 15 h, respectively. On the contrary, the concentration of flavonoids, that ranged from 16.45 (control) to 13.39 (Ph15) mg CE g(-1) d.w., was not influenced by the photoperiodic conditions. The heads of 'Spinoso sardo' artichoke exhibited high radical scavenging activity. The DPPH test showed no differences between plants exposed to Ph15 and Ph17. The concentration of lignin in head tissues ranged from 0.43 (Ph15) to 0.63 (Ph17) g 100 g(-1) d.w. The exposition of Ph17 caused a significant increase of lignin concentration as compared to control. This study suggests the modulation of the photoperiodic conditions as a tool to produce artichoke heads suitable for minimal food processing.