Antioxidant and free radical scavenging activity of potato tubers

The chlorogenic acid and the total polyphenol content were analyzed in two different potato varieties (Kennebec, Agria) grown under five different fertilizer rates (0, 75, 150, 225, 300 kg N ha(-1)). Chlorogenic acid content ranged of 6.0-22.3 mg kg(-1) fresh weight and did not seem to be variety-dependent. The chlorogenic acid in potato tubers makes up 88.9 +/- 10.3 % of the total polyphenols. Free radical scavenging and antioxidant activities of the tubers were also analysed. Ethanolic extracts of the tubers showed marked hydrogen-donating activity in the experiment using 1,1-diphenyl-2-picrylhydrazyl, they had reducing power in the Fe(III) --> Fe(II) reaction but did not exhibit H2O2 scavenging activity assessed with a chemiluminescence method. These data indicated that chlorogenic acid containing extract of potato can act as primary and secondary antioxidant in inhibition of lipid peroxidation. Potato extracts showed weak but significant Cu(II)-chelating activity and inhibited the autoxidation of linoleic acid measured by the thiocyanate method. The strong correlation between the antioxidant activity and the level of total polyphenols suggest that the phenolic compounds are the main effective antioxidant components of whole potato tubers. Potato variety and N fertiliser rate had minimal or no effects on the levels of studied characteristics.