Abstract
In the UV irradiation of 7-dehydrocholesterol, the effect of wavelength on the formation of vitamin D_3 and other isomers was investigated and the results were compared with those on the UV irradiation of ergosterol reported previously^<1)>. The irradiation was carried out by monochromatic UV lights obtained from a spectroirradiator and the yield of vitamin D_3 was estimated by gas liquid chromatography as described previously^<2)>. When a 7-dehydrocholesterol solution in ethanol (1.0mg/ml) was irradiated by monochromatic UV lights in the range 230〜350nm with the quantum energy of 4.0×10^8 erg/cm^2,the figure of the relationship between yield of vitamin D_3 and wavelengths of irradiating UV lights showed a mountain shape with a peak at 295nm. The results were nearly identical with that of ergosterol and moreover there were little differences between the patterns of gas chromatograms of 7-dehydrocholesterol and ergosterol irradiated by the corresponding UV light. It was concluded from these results that the two types of provitamin D must show the same attitude to UV irradiation.
