Development of a new isotopically labeled internal standard for ergosterol measurement by GC/MS.
Environmental exposure to fungi has been associated with a variety of adverse health effects. Ergosterol, a marker of total fungal biomass, can be used to quantify exposure to fungi. Unfortunately, environmental ergosterol measurement using published GC/MS/MS methods is prone to bias introduced by sample matrix effects, resulting in potential measurement inaccuracy. We developed an isotopically labeled internal standard ((13)C ergosterol) for ergosterol quantification by GC/MS/MS, to eliminate bias due to sample matrix effects and selective losses during preparation. To produce (13)C ergosterol, we grew Saccharomyces Cerevisiae on (13)C D-glucose under aerobic conditions at room temperature. The (13)C labeled ergosterol comprised 97.1% of the ergosterol in the dry yeast preparation. Ergosterol spike-recovery from house dust samples averaged 99.3% using the isotopically labeled yeast preparation as the internal standard (I.S.). By contrast, spike-recovery averaged 42.4% when 7-dehydrocholesterol (7-DHC) was the internal standard. Analysis of indoor house dust samples from a large epidemiologic study also showed the systematic underestimation of ergosterol when analyzed using 7-DHC as compared with using the yeast preparation containing the isotopically labeled authentic compound, (13)C-ergosterol.
Sordillo
Joanne
J
Channing Laboratory, Boston, MA, USA.
Vespa
Donato
D
Haggerty
Linda
L
Youngs
Frederick
F
Gold
Diane
D
Milton
Donald
D
D002247:Carbon Isotopes; D003684:Dehydrocholesterols / Q000032:analysis / Q000737:chemistry; D004875:Ergosterol / Q000032:analysis / Q000737:chemistry / Q000592:standards*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods / Q000592:standards*; D005947:Glucose / Q000378:metabolism; D007553:Isotope Labeling; D012015:Reference Standards; D012441:Saccharomyces cerevisiae / Q000378:metabolism
D002247:Carbon Isotopes; D003684:Dehydrocholesterols; C016705:7-dehydrocholesterol; D005947:Glucose; D004875:Ergosterol