Abstract
Riboflavin tetrabutyrate was dissolved in fresh soybean oil to 50 μg/ml, which was irradiated with Mazda daylight lamp. After irradiation for 4 hours, the absorbance at 445 mμ was decreased to 41% of the original absorbance, but the decrease was recovered up to 56% by mere storage in the dark for 48 hours. However, when the solution was irradiated for 10 hours, this recovery remained only 26%. These results suggest that riboflavin tetrabutyrate dissolved in the oil can be partly reduced by irradiation and reversed through slow oxidation. The irreversible reaction could be attributed to the decomposition of the isoalloxazine nucleus of riboflavin tetrabutyrate due probably to its reaction with lipoperoxide produced in the oil upon irradiation.
