School of Chemistry, Monash University, Wellington Road, Clayton, Victoria 3800, Australia.
J Phys Chem B. 2011 Dec 1;115(47):13943-54. doi: 10.1021/jp207730g. Epub 2011 Nov 7.
A series of 5-hydroxy-isoflavones-genistein, biochanin A, prunetin, and 4',7-dimethoxygenistein-have been studied by surface-enhanced Raman spectroscopy (SERS). Citrate reduced silver colloids were employed as a standard technique to measure SER spectra over a range of pH and concentrations. Density functional theory calculations were used to assist in determining the mode of interaction of isoflavones with the silver nanoparticles. It is revealed that biochanin A and prunetin interact with the silver nanoparticles upon deprotonation of the 7- and the 4'-OH groups, respectively, to show SERS activity. Correlations of their spectra with SERS of genistein strongly support the presence of multiple interaction modes involving both of the OH groups in genistein, in a similar manner to daidzein. Surprisingly, however, under these conditions, the 5-OH group was found to be noninteractive as revealed by attempts to measure SERS of 4',7-dimethoxygenistein. This was attributed partly to the low solubility and, more importantly, to the influence of steric hindrance, caused by the position of the pendant phenyl ring, which prevented interaction with the Ag colloid surface. These results complement recent work on daidzein and formononetin and provide further insight into understanding the SER spectra of isoflavones.
一系列 5-羟基异黄酮-染料木黄酮、大豆苷元、芒柄花素和 4',7-二甲氧基染料木黄酮已通过表面增强拉曼光谱（SERS）进行了研究。采用柠檬酸还原银胶体作为标准技术，在一系列 pH 值和浓度下测量 SER 光谱。密度泛函理论计算用于协助确定异黄酮与银纳米粒子相互作用的模式。结果表明，大豆苷元和芒柄花素在 7-和 4'-OH 基团分别去质子化后与银纳米粒子相互作用，表现出 SERS 活性。它们的光谱与染料木黄酮的 SERS 相关性强烈支持存在涉及染料木黄酮中两个 OH 基团的多种相互作用模式，与大豆苷元相似。然而，令人惊讶的是，在这些条件下，尝试测量 4',7-二甲氧基染料木黄酮的 SERS 时，发现 5-OH 基团不具有相互作用。这部分归因于低溶解度，更重要的是，由于侧苯基环的位置引起的空间位阻，阻止了与 Ag 胶体表面的相互作用。这些结果补充了最近关于大豆苷元和芒柄花素的工作，并为进一步理解异黄酮的 SERS 光谱提供了更多的见解。
