Further characterization of human colostral antioxidants: identification of an ascorbate-like element as an antioxidant component and demonstration of antioxidant heterogeneity.
Human colostrum manifests antioxidant properties, being capable of spontaneous reduction of cytochrome c, depletion of polymorphonuclear leukocyte-produced H2O2 and protection of epithelial cells from PMN-mediated detachment. These activities can be electrophoretically concentrated at either 3.5 kD or 50 kD dialysis membranes at mildly alkaline pH. They are progressively lost under increasingly alkaline conditions. They are resistant to 1-mM N-ethylmaleimide. Examination of a series of antioxidant compounds showed that ascorbate manifests several characteristics of colostrum, being able to reduce cytochrome c and deplete H2O2 but not altering PMN-mediated HEp2 cell detachment. Addition of ascorbate oxidase to colostrum decreased its cytochrome c-reducing activity by more than 85%, decreased its H2O2-depleting activity by nearly 50%, but did not alter its ability to protect HEp2 cells, all suggesting heterogeneity of colostral antioxidant activities. Treatment of colostrum with an enzymatic system (xanthine + xanthine oxidase) known to destroy ascorbate's cytochrome c-reducing activity yielded paradoxical results, decreasing colostral cytochrome c reduction in a dose-related manner, while increasing its H2O2-depleting activity. These studies demonstrate that a colostral component similar to ascorbate, a known antioxidant compound is responsible for the majority of colostral cytochrome c-reducing activity, for about half of its H2O2-depleting activity, and little, if any, of its protective effect on HEp2 cells. Thus colostral antioxidant activity is heterogeneous.
Buescher
E S
ES
Department of Pediatrics, University of Texas Medical School, Houston 77030.
McIlheran
S M
SM
Frenck
R W
RW
D000975:Antioxidants / Q000032:analysis* / Q000494:pharmacology; D001205:Ascorbic Acid / Q000032:analysis* / Q000494:pharmacology; D003126:Colostrum / Q000032:analysis*; D003574:Cytochrome c Group / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction; D010545:Peroxides / Q000378:metabolism; D011247:Pregnancy
D000975:Antioxidants; D003574:Cytochrome c Group; D010545:Peroxides; D001205:Ascorbic Acid