Abstract

The photosensitive effects of riboflavin, flavin mononucleotide, flavin adenine dinucleotide, and a commercial multivitamin infusate on a lipid emulsion used in parenteral nutrient infusions were studied during exposure to polychromatic visible light. It was found that the efficiency of riboflavin (a polar flavin) as sensitizer of lipid emulsion peroxidation is greater than that of flavin mononucleotide (an ionic flavin). This was determined by measuring the consumption of molecular oxygen and the concentration of thiobarbituric acid-reactive species generated during the irradiation time. These findings are supported by molecular orbital studies of these molecules related to polarity, ionic charges around the different molecular regions, and electrostatic potentials comparisons. Flavin adenine dinucleotide (a more ionic flavin), most likely remains totally excluded from the lipid emulsion due to its polarity and molecular geometry and does not induce lipid peroxidation. The multivitamine complex seems to provide a protective effect on the lipid emulsion exposed to light, attributed to the presence of ascorbic acid, which suffers an intensive photodecomposition. A solution of vitamin C, whose concentration was equivalent to that of the parenteral mixture, consumes a considerable amount of molecular oxygen when it is irradiated with visible light in the presence of flavin mononucleotide.