Phenolic acids in potatoes, vegetables, and some of their products

The aim of this study was to determine the distribution and contents of soluble and total phenolic acids in a wide range of vegetables consumed in Finland. The determinations were performed from the pooled samples (14 potato and 45 other vegetable samples). Soluble phenolic acids were extracted with methanolic acetic acid and a tentative quantification was performed by HPLC. The contents of total phenolic acids were determined by HPLC after alkaline and acid hydrolyses. Chlorogenic acid derivatives were the most dominant soluble phenolic acids, while caffeic acid was the most dominant phenolic acid aglycone in the samples studied. Highest contents of soluble phenolic acids were found in raw and cooked potato peels: 23–45 mg/100 g fresh weight calculated as aglycones. In addition, pot-grown lettuces, Chinese cabbage, broccoli, carrot, aubergine, Jerusalem artichoke, peanut and most of the boiled and peeled potato tubers contained more than 5 mg/100 g of soluble phenolic acids calculated as aglycones. Among the best vegetable sources of total phenolic acids were potatoes, with contents varying from 7.9 mg/100 g (cooked and peeled Rosamunda variety) to 52 mg/100 g (cooked peel of Van Gogh variety), and red cabbage, carrot, aubergine, Jerusalem artichoke, broccoli, pot-grown lettuce, spinach, radish and red beet, with contents from 11 mg/100 g (spinach) to 52 mg/100 g (pot-grown lettuce Lollo Rosso). Variation in the phenolic acid contents of the vegetables was either moderate or considerable and needs further research.