Enzyme immunoassay for mycophenolic acid in milk and cheese.
Mycophenolic acid (MPA) was reacted with N-hydroxysuccinimide and conjugated to keyhole limpet hemocyanin (KLH), and to horseradish peroxidase (HRP), respectively. The MPA-KLH was used to produce anti-MPA antiserum in rabbits. A competitive direct enzyme immunoassay (EIA) for MPA was established with anti-MPA antiserum and MPA-HRP conjugate. The mean 50% inhibition and detection limit of MPA standard curves (n = 103) were 197 +/- 67 and 81 +/- 48 pg/mL, respectively. The EIA was specific for MPA and its synthetic 2-morpholinoethyl ester, mycophenolate mofetil (91% relative cross-reactivity). Raw bulk milk and pasteurized milk, with and without beta-glucuronidase pretreatment, were analyzed by EIA. No MPA was found in milk, at a detection limit of 100 pg/mL (recovery 58-66% at 0.125-2 ng/mL). Blue-veined cheese from the German market (n = 53) was analyzed by EIA, and the detection limit was at 0.5 ng/g (recovery 68-79% at 5-100 ng/g). All but two cheeses contained MPA, although mostly (66%) at levels of <10 ng/g. MPA at 400-1200 ng/g was found in Roquefort cheeses. Highest levels (4-11 microg/g) were found in a German soft cheese preparation. MPA levels in mycelium-rich parts of cheese were 3 times higher than in mycelium-free parts.
Usleber
Ewald
E
Institute of Veterinary Food Science, Veterinary Faculty, Justus-Liebig-University, Ludwigstrasse 21, 35390 Giessen, Germany. ewald.usleber@vetmed.uni-giessen.de
Dade
Melanie
M
Schneider
Elisabeth
E
Dietrich
Richard
R
Bauer
Johann
J
Märtlbauer
Erwin
E
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000032:analysis*; D002611:Cheese / Q000032:analysis*; D007106:Immune Sera / Q000096:biosynthesis; D007124:Immunoenzyme Techniques / Q000379:methods*; D008892:Milk / Q000737:chemistry*; D009173:Mycophenolic Acid / Q000032:analysis*; D011817:Rabbits; D012680:Sensitivity and Specificity
D000903:Antibiotics, Antineoplastic; D007106:Immune Sera; D009173:Mycophenolic Acid