title: Trolox equivalent antioxidant capacity of different geometrical isomers of alpha-carotene, beta-carotene, lycopene, and zeaxanthin.
abstract: Isomerization of carotenoids, which is often encountered in food processing under the influence of temperature and light, may play a role in the observed protective effects of this group of secondary plant products. Investigation of in vitro antioxidant activity of prominent carotenoid geometrical isomers was undertaken in light of recent reports illustrating a large percentage of carotenoid (Z)-isomers in biological fluids and tissues. Alpha-carotene, beta-carotene, lycopene, and zeaxanthin were isolated from foods or supplements and subsequently photoisomerized with iodine as a catalyst. Major Z-isomers of each carotenoid were fractionated by semipreparative C(30) HPLC. In vitro antioxidant activity of all isomers collected was measured photometrically using the Trolox equivalent antioxidant capacity (TEAC) assay. TEAC values of 17 geometrical isomers investigated ranged from 0.5 to 3.1 mmol/L. Three unidentified (Z)-isomers of lycopene showed the highest antioxidant activity, being significantly higher than the result for (all-E)-lycopene, which had approximately two times the activity of (all-E)-beta-carotene. On the other hand, (9Z)-zeaxanthin had a more than 80% lower TEAC value compared to that of (all-E)-lycopene. These results allow for the in vivo relevance of (Z)-isomers of carotenoids to be considered.
authors.affiliation: Institute of Nutrition, Friedrich Schiller University Jena, Dornburger Strasse 25-29, 07743 Jena, Germany. Volker.Boehm@rz.uni-jena.de
authors.forename: Volker
authors.initials: V
authors.lastname: Böhm
authors.forename: Ni Luh
authors.initials: NL
authors.lastname: Puspitasari-Nienaber
authors.forename: Mario G
authors.initials: MG
authors.lastname: Ferruzzi
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Schwartz
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism*; D002338:Carotenoids / Q000737:chemistry / Q000378:metabolism*; D002839:Chromans / Q000737:chemistry / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D000077276:Lycopene; D013237:Stereoisomerism; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism
chemical_list: D000975:Antioxidants; D002839:Chromans; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; D002338:Carotenoids; C041635:alpha-carotene; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; D000077276:Lycopene