ARS | Publication request: EVALUATION OF THE ANTIOXIDANT CAPACITY OF LIMONIN, NOMILIN AND LIMONIN GLUCOSIDE

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 4, 2006
Publication Date: May 3, 2006
Citation: A.P. Breksa III, G.D. Manners, 2006. Evaluation of the Antioxidant Capacity of Limonin, Nomilin and Limonin Glucoside. Journal of Agricultural and Food Chemistry. V54:3827-3831.

Interpretive Summary: The growing importance of foods to provide more than nourishment from both consumers and the media has lead to an explosion in the development of methods and reports of the analysis of the foods we eat and the constituents therein for biological activities relevant to maintaining or improving human health and nutrition. Chief among these many assessments is the determination of antioxidant capacity (AOC). Pure citrus limonoids were evaluated by four methods and shown not to be antioxidants.

Technical Abstract: In an effort to resolve conflicting reports of the antioxidant properties of citrus limonoids, the Antioxidant Capacity (AOC) of citrus limonoids limonin, nomilin and limonin glucoside was evaluated by the oxygen radical absorbance capacity (ORAC), Trolox equivalent antioxidant capacity (TEAC), beta-carotene-linoleic acid bleaching and 1,1,-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging assays. Assays were conducted using pure limonoids and included cinnamic acid as the negative control and 2,6-di-tert-butyl-4-methylphenol (BHT) and ascorbic acid as positive controls. In all cases, limonin and nomilin gave results equivalent to cinnamic acid indicating that they do not possess any inherent AOC and should not be considered antioxidants. Similar results were obtained for limonin glucoside, with the exception of the beta-carotene-linoleic acid bleaching assay. Under the conditions of this assay, the presence of limonin glucoside was found to afford some protection against the auto-oxidation of beta-carotene. However in light of the results of the other three assays we concluded that limonin glucoside, like the other limonoids, should not be considered an antioxidant.