Polyphenol content in cultivated cardoon (Cynara cardunculus L. var. altilis DC.) leaves as affected by intraspecific plant competition

Polyphenols, a large group of secondary metabolites widely distributed in plants, have received considerable attention, as they act as powerful scavengers of harmful radicals and, thus, can be protective against chronic diseases such as cancer and cardiovascular malfunction. Their content is influenced by several biotic and abiotic factors. In this light, this study aimed to evaluate the influence of intraspecific plant competition, determined by plant density, on the total caffeoylquinic acids (CCs), chlorogenic acid (CGA), flavonoids (Fs), and cynaropicrin (Cp) content of cultivated cardoon leaf blades over two cutting times. The leaf blade yield was also considered. The polyphenols profile was determined by HPLC analysis. Effects of intraspecific plant competition were shown in both cutting times (early May and late June). In particular, the total content of CCs and Fs decreased, respectively, by about 16 and 15% passing from high to low intraspecific plant competition, while both CGA and Cp reported a decrease of about 10%. The phenolic acids had the greatest value during the second cutting time, whereas Fs and Cp in the first. In conclusion, the intraspecific plant competition could have a key role in the polyphenol content although the effect was also time-dependent.