title: Quantitative analyses of beta-carotene and retinol in serum and feces in support of clinical bioavailability studies.
abstract: Among more than 50 provitamin carotenoids, beta-carotene is the most metabolically active source of retinol. Despite diets rich in fruits and vegetables containing beta-carotene, vitamin A deficiency is the leading cause of blindness and childhood mortality in developing countries. In addition, the uncertainty of beta-carotene bioconversion into vitamin A suggests that new data are needed to update the nutritional guidelines in developed countries. Previously, we reported the development of a carotene/retinol plateau isotopic enrichment method (CarRet PIE) for the determination of beta-carotene bioavailability and bioconversion into retinol, which utilizes positive ion atmospheric pressure chemical ionization (APCI) liquid chromatography/mass spectrometry (LC/MS). While seeking to validate the CarRet PIE using a mass balance approach requiring fecal measurements of beta-carotene and retinol, interference was encountered that required substantial modifications of the LC/MS assay. Here we report a new LC/MS assay that is based on the detection of molecular anions of beta-carotene using negative ion APCI with a reversed-phase C30 column for HPLC separation. Sample preparation required saponification to eliminate interfering triglycerides. The limit of detection (LOD) of beta-carotene was 0.25 pmol calculated on the basis of an injection of 20 microL of 0.0125 microM beta-carotene, and the limit of quantitation (LOQ) was 1.0 pmol based on the injection of 20 microL of 0.050 microM beta-carotene. The linear range was 1.1 to 2179 pmol on-column. The wide linear range and low LOD and LOQ of this assay facilitated the sensitive and selective quantitative analysis of beta-carotene in both serum and fecal samples in support of an on-going clinical investigation of beta-carotene bioavailability and bioconversion into vitamin A.
authors.affiliation: College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA.
authors.forename: Dongwei
authors.initials: D
authors.lastname: Zhu
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Yan
authors.initials: Y
authors.lastname: Pang
authors.forename: Ang
authors.initials: A
authors.lastname: Liu
authors.forename: Jian
authors.initials: J
authors.lastname: Guo
authors.forename: Carolien A
authors.initials: CA
authors.lastname: Bouwman
authors.forename: Clive E
authors.initials: CE
authors.lastname: West
authors.forename: Richard B
authors.initials: RB
authors.lastname: van Breemen
mesh_terms: D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005243:Feces / Q000737:chemistry*; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D015203:Reproducibility of Results; D014801:Vitamin A / Q000032:analysis* / Q000097:blood / Q000493:pharmacokinetics; D019207:beta Carotene / Q000032:analysis* / Q000097:blood / Q000493:pharmacokinetics
chemical_list: D019207:beta Carotene; D014801:Vitamin A