Abstract
Processing of onion and potato produces a large amount of discards, mainly skins. This study compared the antioxidant activity of skin and flesh phenolics of selected onion (Pearl, Red, Yellow and White) and potato (Purple, Innovator, Russet and Yellow) varieties. All tests were carried out separately for the soluble and insoluble-bound phenolic constituents of onion and potato samples. The potency of the phenolic extracts in the inhibition of radical-induced DNA scission, human low-density lipoprotein (LDL) cholesterol oxidation and LPS-stimulated cyclooxygenase-2 (COX-2) expression in J774A.1 mouse macrophage cells were monitored. Results showed that the soluble extracts had a higher phenolic content and antioxidant activity than the insoluble-bound extracts in most of the assays. Both onion and potato phenolics exhibited notable inhibition of LDL cholesterol oxidation, DNA scission and COX-2 expression at concentrations as low as 5 mu g/mL. Pearl onion skin and Purple potato peel phenolics exhibited the highest activities among the tested onion and potato varieties, respectively. (c) 2013 Elsevier Ltd. All rights reserved.