Quantitation of red blood cell folates by stable isotope dilution gas chromatography-mass spectrometry utilizing a folate internal standard.
We report a new gas chromatography-mass spectrometry (GC-MS) method of measurement of red blood cell folates utilizing a stable isotope-labeled bacterial synthesized folate internal standard. The GC-MS method exploits the fact that the common feature of all folate molecules is a p-aminobenzoic acid moiety sandwiched between a pteridine ring and a polyglutamate chain of varying length. In this method, red blood cell folates together with a folate internal standard are specifically purified using bovine folate binding protein and the folates are subsequently chemically cleaved to p-aminobenzoic acid, pteridines, and glutamic acids. Since all six carbon atoms of the benzene ring in the p-aminobenzoic acid moiety of the folate internal standard are labeled with [13C], it is possible to use selected ion monitoring and stable isotope dilution GC-MS to quantitate folates. The method appears to be sensitive, specific, and accurate. The method has been applied to generate a reference range of red blood cell folates based on assay of 25 normal individuals.
Santhosh-Kumar
C R
CR
Division of Hematology, University of Colorado Health Sciences Center, Denver, USA.
Deutsch
J C
JC
Hassell
K L
KL
Kolhouse
N M
NM
Kolhouse
J F
JF
D010129:4-Aminobenzoic Acid / Q000378:metabolism; D000818:Animals; D002247:Carbon Isotopes; D002352:Carrier Proteins / Q000378:metabolism; D002417:Cattle; D004912:Erythrocytes / Q000737:chemistry*; D058973:Folate Receptors, GPI-Anchored; D005492:Folic Acid / Q000096:biosynthesis / Q000097:blood*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D007778:Lactobacillus / Q000378:metabolism; D011956:Receptors, Cell Surface; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D002247:Carbon Isotopes; D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D011956:Receptors, Cell Surface; D005492:Folic Acid; D010129:4-Aminobenzoic Acid