Colostral antioxidants: separation and characterization of two activities in human colostrum.

Human colostrum contains several antioxidants which prevent the detection of human polymorphonuclear leukocyte (PMN) respiratory burst products. Using column chromatography to fractionate colostrum, two peaks of antioxidant activity were resolved away from colostral proteins and further characterized. One peak contained both cytochrome c-reducing activity and H2O2-depleting activity. This peak had the chromatographic, spectral, and antioxidant characteristics of ascorbate, and by high performance liquid chromatography (HPLC) methods, was shown to contain ascorbate as well as at least four other materials. The antioxidant activity in this peak was totally ascorbate oxidase sensitive and partially uricase sensitive. The other peak contained only H2O2-depleting activity and had the chromatographic, spectral, and antioxidant characteristics of uric acid. By HPLC, uric acid was the only component in this peak and its antioxidant activity was completely uricase sensitive and ascorbate oxidase resistant. Colostral uric acid levels were measured in eight postpartum women and found to be approximately one-third of simultaneously determined serum uric acid levels. Colostrum contains at least two separate antioxidants, one of which is ascorbate-like and the other is uric acid. We speculate that these antioxidants may function in human colostrum as traps for neutrophil-generated reactive oxygen metabolites.