Surface‐enhanced Raman scattering characterization of monohydroxylated polymethoxyflavones

Abstract

Polymethoxyflavones (PMFs) belong to a unique class of flavonoids mainly found in citrus fruits. Characterization of different PMFs is important to further understand and apply these compounds as functional ingredients in food. The objective of this study is to characterize three monohydroxylated PMFs using surface-enhanced Raman spectroscopy (SERS) and to determine the role of hydroxylation in their SERS behaviors. Serial concentrations of 3′-hydroxylnobiletin (3HN), 4′-hydroxylnobiletin (4HN), and 5-hydroxylnobiletin (5HN) were incubated with silver dendrites for SERS analysis. Results demonstrated that three PMFs exhibited significantly different SERS behaviors. 5HN produced saturation peak intensity at relative low concentration (0.05 mM), while 3HN and 4HN produced saturation peak intensity at much higher concentrations (0.5 and 1 mM, respectively) according to principal component analysis. Below saturation, 5HN had the highest peak intensity, while 3HN had the lowest peak intensity. After reaching saturation, 4HN and 5HN had similar relative peak intensities that were much greater than 3HN. The HPLC analysis revealed that 36.13 ± 1.06% of 5HN, 18.40 ± 3.31% of 4HN, and 9.66 ± 0.94% of 3HN were bound to silver. Based on these results, we speculated that different positions of hydroxylation of PMFs were critical for determining spatial conformation of PMFs on binding sites, resulting in different binding affinities and saturation points, therefore their SERS behaviors. This study first reported that the position of hydroxylation in the monohydroxylated PMFs was crucial for their interactions with silver dendrites and provided valued information for further applying SERS for molecular characterization of flavonoids.

Label free hepatitis B detection based on serum derivative surface enhanced Raman spectroscopy combined with multivariate analysis

“…The method for data processing of derivative spectrum has already been reported in some aspects of UV spectra and near infrared spectra [26,27]. Moreover, the first-order derivative spectrum has been used to analyze Raman spectral of Chinese medicine, organic material and so on [28][29][30]. But the application of derivative spectrum in SERS spectra statistical analysis has not been reported.…”

Simultaneous determination of 14 bioactive citrus flavonoids using thin-layer chromatography combined with surface enhanced Raman spectroscopy

“…The time for these procedures was about 3 min. Meanwhile, the substrate method for SERS analysis reported in our previous study was used here (Ma et al, 2016). In brief, 5 μL of Ag dendrites were deposited onto a glass slide first and air-dried.…”

“…In the past few years, SERS has been widely used in different fields, such as materials science, various engineering disciplines, medical science, food science and so on (Zheng & He, 2014). Recent studies have also proven the capacity of SERS for the characterization of citrus flavonoids (Ma, Xiao & He, 2016;Zhang et al, 2018;Zheng, Fang, Cao, Xiao & He, 2013). However, it remains difficult to differentiate citrus flavonoid analogs in real samples by virtue of their similar chemical structures, as well as interference of other components in the complex matrix.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part XI

“…Ma and co‐workers used SERS to characterize monohydroxylated polymethoxyflavones. The objective of their study was to characterize three monohydroxylated PMFs using surface‐enhanced Raman spectroscopy (SERS) and to determine the role of hydroxylation in their SERS behaviours . Prakash et al studied the characteristics of a hybrid SERS substrate CuO:Mn/Ag heterojunction probed by methyl orange to determine effect of Mn 2+ doping.…”

“…The objective of their study was to characterize three monohydroxylated PMFs using surface-enhanced Raman spectroscopy (SERS) and to determine the role of hydroxylation in their SERS behaviours. [37] Prakash et al studied the characteristics of a hybrid SERS substrate CuO:Mn/Ag heterojunction probed by methyl orange to determine effect of Mn 2+ doping. They observed that with Mn-doping in the lattice of CuO, the SERS signal is enhanced considerably because of ferromagnetic ordering in CuO:Mn.…”