title: Similar metabolites formed from beta-carotene by human gastric mucosal homogenates, lipoxygenase, or linoleic acid hydroperoxide.
abstract: To determine the basis for the formation of excentric cleavage products of beta-carotene (beta-C) after incubation with human gastric mucosal homogenates, we have studied the effect of lipoxygenase in beta-C metabolism. beta-C was incubated with human gastric mucosal homogenates, soybean lipoxygenase with linoleic acid, or the lipoxygenase primary product, 13(S)-hydroperoxycis,trans-9,11-octadecadienoic acid (13-LOOH). The beta-C metabolites, beta-apo-14', -12', -10', and -8'-carotenals, beta-apo-13-carotenone, retinoic acid, and retinal were detected and quantified by HPLC after a 30-min incubation with 1.8 microM beta-C. The products from the lipoxygenase plus linoleic acid incubation and from the lipoxygenase primary product, 13-LOOH, with beta-C were exactly the same as the products from a human gastric mucosal homogenate incubation. Significantly larger amounts of the same beta-C metabolites were formed when beta-C was incubated with gastric mucosal homogenates and lipoxygenase together. Furthermore, nordihydroguaiaretic acid (NDGA), a specific lipoxygenase inhibitor, was found to significantly inhibit the formation of beta-apo-carotenoids and retinoids produced by gastric mucosal homogenates incubated with beta-C. The similarity of the beta-C metabolites when beta-C was incubated with human gastric mucosal homogenate, lipoxygenase plus linoleic acid, or 13-LOOH and the inhibition of beta-C metabolite production by NDGA in gastric tissue incubation with beta-C suggest that lipoxygenase is involved in beta-C metabolism in gastric mucosa. The activity of 13-LOOH in our hands would indicate that an enzyme-linked process is occurring in gastric tissue producing fatty acid hydroperoxides, and that the hydroperoxide, or a radical species derived from it, is able to carry out the oxidation of beta-C independently of the enzyme.
authors.affiliation: United States Department of Agriculture, Human Nutrition Research Center on Aging, Boston, Massachusetts, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Yeum
authors.forename: Y C
authors.initials: YC
authors.lastname: Lee-Kim
authors.forename: S
authors.initials: S
authors.lastname: Yoon
authors.forename: K Y
authors.initials: KY
authors.lastname: Lee
authors.forename: I S
authors.initials: IS
authors.lastname: Park
authors.forename: K S
authors.initials: KS
authors.lastname: Lee
authors.forename: B S
authors.initials: BS
authors.lastname: Kim
authors.forename: G
authors.initials: G
authors.lastname: Tang
authors.forename: R M
authors.initials: RM
authors.lastname: Russell
authors.forename: N I
authors.initials: NI
authors.lastname: Krinsky
mesh_terms: D001711:Biotransformation; D002338:Carotenoids / Q000737:chemistry* / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005753:Gastric Mucosa / Q000378:metabolism*; D006801:Humans; D008041:Linoleic Acids / Q000737:chemistry*; D008054:Lipid Peroxides / Q000737:chemistry*; D008084:Lipoxygenase / Q000378:metabolism*; D012016:Reference Values; D013025:Glycine max / Q000201:enzymology; D013274:Stomach Neoplasms / Q000378:metabolism; D019207:beta Carotene
chemical_list: D008041:Linoleic Acids; D008054:Lipid Peroxides; D019207:beta Carotene; C008285:linoleic acid hydroperoxide; D002338:Carotenoids; D008084:Lipoxygenase