PARADOXICAL ROLE OF ASCORBIC-ACID AND RIBOFLAVIN IN SOLUTIONS OF TOTAL PARENTERAL-NUTRITION - IMPLICATION IN PHOTOINDUCED PEROXIDE GENERATION

In the presence of light, a multivitamin preparation is the main sourc e of peroxides in solutions of total parenteral nutrition (TPN). This preparation contains two photosensitive products, 5'-phosphate flavin mononucleotide (FMN) and polysorbates (PS), as well as electron donors such as ascorbate (AH). We hypothesized that the admixture of FMN or PS with electron donors generates peroxides in TPN and alters the qual ity of nutrients. Using xylenol orange, peroxide concentrations were m easured in solutions containing AH, FMN, and/or PS in water, a dextros e solution, an amino acid preparation, and a lipid emulsion. Thiol fun ctions were evaluated by reduction of 5,5-dithiobis(2-nitrobenzoic aci d) in the amino acid preparation. After 24-h light exposure, dextrose solutions with admixtures of AH + FMN or AH + FMN + PS generated perox ides at concentrations similar to those observed in a 1% multivitamin solution, and over three times higher than those observed with FMN, PS , or AH alone. However, in the presence of amino acids, FMN alone indu ced a generation of peroxides comparable to that observed with FMN + A H. In the lipid emulsion, peroxides increased over 3-fold in the prese nce of FMN or FMN + AH. The addition of catalase suggested that lipid peroxides and H2O2 were produced, and the loss of thiol function sugge sted that an oxidation of amino acids occurred. When exposed to light, FMN induces reactions with amino acids, polyunsaturated fatty acids, and even AH, altering the quality of nutrients. Paradoxically, AH with out FMN has a protective effect on peroxide generation in TPN.