The resveratrol functionalized carboxymethyl-
Resveratrol, 3,4′,5-trihydroxystilbene (Figure
The structure of resveratrol.
Cyclodextrins (CDs) are a class of macrocyclic oligosaccharides, which come from enzymatic reaction. According to the number of the linked glucose units, cyclodextrins can be divided into three classes (
Due to the low solubility of
CM-
NMR spectra were recorded in DMSO-
FTIR spectra were obtained from solid samples such as KBr disks using a Perkin Elmer Spectrum GX, which is a singlebeam, Michelson interferometer-based, Fourier transform infrared spectrometer. The spectra were measured over a range of 4,000–400 cm−1 with a resolution of 4 cm−1.
Samples for the photostability study were irradiated at 365 nm in ZF-20D which is the UV chemical reactor. Samples were always placed 10 cm from the lamp and irradiated over a range of time periods to a maximum of 360 min. Solution samples were placed in a 50 mL volumetric flask.
Resveratrol (0.0015 g, 6.58 × 10−6 mol) was dissolved in 50% of the methanol solution (10 mL) to give a final concentration of solution (6.58 × 10−4 mol/L).
CDRes (0.0015 g, 1.12 × 10−6 mol) was dissolved in 50% of the methanol solution (10 mL) to give a final concentration of the solution (1.12 × 10−4 mol/L).
CM-
CM-
Elemental analysis: C, 47.89; H, 5.32; O, 46.48.
FTIR (cm−1): 1734 (C=O), 1161 (phenyl), 849 (
1H NMR (400 MHz, DMSO-
13C NMR (101 MHz, DMSO-
Supplementary data for 1H, 13C NMR spectra of CDRes are available
The schematic structure of CDRes is shown in Figure
The schematic structure of the CDRes.
The synthesis of conjugate is a typical esterification process which belongs to the affinity addition-elimination reaction. In this study, it can be inferred that the reaction mechanism of the carboxylic acid ester obeys nucleophilic addition reaction mechanism. Among them, the carboxymethyl chloride-
The reaction mechanism of the process.
FTIR has a very wide range of applications in the field of identifying compound groups. Figure
The absorption peaks by FTIR: (a) CDRes and (b) raw material of CM-
The NMR spectrum was used for the structure analysis of CM-
The photostability of the compound was studied under the UV light-irradiating condition. The UV absorption spectra of resveratrol, inclusion complex of resveratrol with CM-
UV absorption spectra of aqueous solutions of three different solutions irradiated over 360 min: (a) the solution of resveratrol (Res), (b) the solution of inclusion complexes (CD + Res), and (c) the solution of conjugate (CDRes).
The irradiation of light can affect the stability of resveratrol. It can be clearly seen from Figure
The results of the absorbance of three solutions at different times are shown in Table
Absorbance at 305 nm of resveratrol (Res), CDRes, and inclusion complex of CM-
Exposure time to |
|
|
|
|
|
|
---|---|---|---|---|---|---|
0 | 0.339 | 0 | 0.351 | 0 | 0.341 | 0 |
30 | 0.288 | 0.051 | 0.34 | 0.011 | 0.309 | 0.032 |
60 | 0.283 | 0.056 | 0.338 | 0.013 | 0.308 | 0.033 |
120 | 0.268 | 0.071 | 0.33 | 0.021 | 0.298 | 0.043 |
180 | 0.243 | 0.096 | 0.319 | 0.032 | 0.282 | 0.059 |
240 | 0.236 | 0.103 | 0.316 | 0.035 | 0.272 | 0.069 |
300 | 0.231 | 0.108 | 0.311 | 0.04 | 0.262 | 0.079 |
360 | 0.23 | 0.109 | 0.307 | 0.044 | 0.259 | 0.082 |
Difference in degradation conversion versus length of time of irradiation of 360 min for 50% of the methanol solution samples.
Degradation percentages at 305 nm of resveratrol (Res), CDRes, and inclusion complex of CM-
Exposure time to |
|
|
|
---|---|---|---|
0 | 0 | 0 | 0 |
30 | 15.04 | 3.13 | 9.38 |
60 | 16.52 | 3.70 | 9.68 |
120 | 20.94 | 5.98 | 12.61 |
180 | 28.31 | 9.12 | 17.30 |
240 | 30.38 | 9.97 | 20.23 |
300 | 31.86 | 11.39 | 23.17 |
360 | 32.15 | 12.54 | 24.05 |
An effective method of the synthesis of cyclodextrin-resveratrol conjugate has been successfully developed. The conjugate is fully characterized by NMR, UV, and FTIR. Since cyclodextrin reacts with resveratrol to form a stable ester bond, the photostability of the conjugate is improved compared to the parent resveratrol and its inclusion complex. These results suggest that CDRes may provide a stable way of resveratrol. Furthermore, it can provide a new idea of the resveratrol formulation as a potential food additive with multifunctionalities.
The (NMR, FTIR, and UV) data used to support the findings of this study are included within the article.
The authors declare no conflicts of interest.
The authors Jin Gui Cheng and Bing Ren Tian contributed equally to this work.
The authors gratefully acknowledge the financial support of the Natural Science Foundation of China (nos. 21506104 and 21666031).
The supplemental material file briefly describes the 1D 1H, 1D 13C NMR spectra of the conjugates (CDRes).