Polyphenolic profile and antioxidant properties of globe artichokes exposed to environmental pollutants.

Globe artichoke (Cynara cardunculus var. scolymus L.) is an edible vegetable largely used in the Mediterranean diet; furthermore the extract of its leaves is widely used in medicine as hepatoprotectant and choleretic agent. This plant also has a preference for cooler climates, such as of Sicily (Italy); best growth is in poor and porous soil. Globe artichoke represents a natural source of phenolic acids, such as cynarin (1,3-dicaffeoylquinic acid) and its biosynthetic precursor chlorogenic acid (5-caffeoylquinic acid), and flavonoids, such as luteolin, apigenin and its glucosides. It is well known that metabolic profiling of plant organisms can be influenced by their exposure to biotic and abiotic stressors, including environmental pollution. Thus, in our study, globe artichoke samples collected in an urban area close to a petrochemical plant of Gela (Sicily, Italy), have been analyzed with respect to their contaminant content (heavy metals and polycyclic aromatic hydrocarbons, PAHs), the polyphenolic profile (caffeoyl esters and flavonoids) and the antioxidant/free radical scavenger power (that is strictly correlated to the polyphenolic composition) determined through Ferric Reducing/Antioxidant Power (FRAP), total phenols, Trolox Equivalent Antioxidant Capacity (TEAC), Beta Carotene Bleaching (BCB) and iron chelating activity. In fact the city of Gela suffers severe anthropogenic pressure, due to petrochemical plant located close to the town and several mechanical industries related to the refinery. Control samples were collected in an area far from industrial plants (Manfria, Gela). PAHs were analyzed by HPLC coupled with fluorimetric detector and heavy metal (Pb, Cd, V, Ni, As) by atomic absorbtion spectrophotometer. The amount of caffeoyl esters and flavonoids in the hydroalcholic extract (ethanol/water 70/30 v/v) obtained from artichoke foliar disks and outer bracts was determined by HPLC-UV-VIS analysis. The more interesting result was that there is no negative correlation between the polyphenolic content (and consequently the antioxidant power) and the contaminant levels in artichoke foliar disks (the artichoke portion with the highest PAHs content and thus more exposed to the action of those abiotic stressor). Furthermore, the luteolin/luteolin7-O-glucoside content appeared different between samples from Gela and controls. In conclusion our data seem to demonstrate that the exposure of artichokes to environmental pollutants does not cause a significant decrease in plant polyphenolic content and antioxidant power. However, this cannot be considered as a sign of product quality given that intake of foods contaminated by PAHs and heavy metals represents an evident risk for human health