Vukicevic M, Randeberg L L, Boschker J E, Tybell T, Tonnesen H H
Pharmazie. 2014 Feb;69(2):117-24.
Two different qualities of riboflavin (RF) i.e., synthetic (RFs) and biosynthetic riboflavin (RFbs) have been investigated with respect to photoinduced color change in the solid state. Several methods (XRD, FT-IR, VIS-, NIR- and fluorescence spectroscopy) were employed to elucidate the properties of the crystalline structure of RFs and RFbs and the influence of irradiation on the color and structural changes of the samples in the solid state. It was shown that RFs an RFbs represent two different crystal modifications of riboflavin and that RFbs can easily be transformed into a dihydrate upon exposure to humidity. Based on the observed irreversible color change and reduction in fluorescence intensity upon irradiation, an irreversible photoreduction of the molecule was assumed in case of RFs. A more pronounced, reversible color change and reversible reduction in fluorescence intensity indicated a reversible photoreduction process in the case of RFbs. The mechanism of these processes was further investigated by means of NIR and FT-IR spectrophotometry. It is apparent from the current study that the crystal modification of RF can strongly influence the solid state photochemistry of this molecule.
就固态下光致变色而言，已对两种不同品质的核黄素（RF），即合成核黄素（RFs）和生物合成核黄素（RFbs）进行了研究。采用了几种方法（X射线衍射、傅里叶变换红外光谱、可见、近红外和荧光光谱）来阐明RFs和RFbs晶体结构的性质以及辐照对固态样品颜色和结构变化的影响。结果表明，RFs和RFbs代表核黄素的两种不同晶体变体，并且RFbs在暴露于湿度时很容易转化为二水合物。基于观察到的辐照后不可逆的颜色变化和荧光强度降低，假设RFs情况下分子发生了不可逆的光还原。更明显的可逆颜色变化和荧光强度的可逆降低表明RFbs情况下存在可逆的光还原过程。通过近红外和傅里叶变换红外分光光度法进一步研究了这些过程的机制。从当前研究中可以明显看出，RF的晶体变体可强烈影响该分子的固态光化学。
