Analysis and discrimination of integral structure of Paeoniae Radix Alba and Paeoniae Radix Rubra and their alcohol extracts by infrared spectroscopy / 中草药

ABSTRACT

Objective: The Fourier transform infrared spectroscopy (FT-IR) and two-dimension IR correlation infrared spectroscopy (2D-IR) were used for the identification of Paeoniae Radix Alba and Paeoniae Radix Rubraand their alcohol extracts. Methods: The FT-IR spectra method and 2D-IR correlation spectra method were used. Results: The structural information of samples indicated that Paeoniae Radix Alba and Paeoniae Radix Rubra contained a large amount of calcium oxalate and starch, since some characteristic absorption peaks of the calcium oxalate could be observed; And some characteristic absorption peaks in the range of 950-1 200 cm-1 of the starch can be observed, but their shape and location revealed minor differences. In the secondary derivative infrared spectra (SD-IR), both Paeoniae Radix Alba and Paeoniae Radix Rubra can be observed with the characteristic absorption peaks which in 518/517, 989 cm-1 and so on. Besides, these peaks at 989, 1 015, 1 052, 1 078, 1 105, and 1 161 cm-1 of Paeoniae Radix Rubra, almost of them which are single peak, were stronger than Paeoniae Radix Alba's and the same peaks in Paeoniae Radix Alba were jagged peaks, showing that the difference were related to the contents and structure of starch in Paeoniae Radix Alba and Paeoniae Radix Rubra. The characteristic absorption peaks of the peoniflorin which arouse at 1 716, 1 451, 1 347, 1 277, and 714 cm-1 in the FT-IR spectra of their alcohol extracts can be found. Moreover, the shape and intensity of the peaks were more distinct in the secondary derivative IR spectra of the different parts. For example, in the range of 900-980 cm-1, Paeoniae Radix Alba presented two groups of peaks 935, 919 cm-1 (strong) and 962, 949 cm-1 (weak), while Paeoniae Radix Rubraonly presented one group of peaks 941, 920 cm-1 (middle), showing that the difference was related to the content and structure of glucoside in Paeoniae Radix Alba and Paeoniae Radix Rubra. In the 2D-IR spectra, both had five auto-peaks at 887, 968, 1 008, 1 190, and 1 305 cm-1, which were the auto-peaks of glucoside, but the strongest auto-peak of Paeoniae Radix Alba was at 1 190 cm-1 and that of Paeoniae Radix Rubra's was at 968 cm-1. The spectra testified the glucoside compounds in Paeoniae Radix Alba and Paeoniae Radix Rubra were different. Conclusion: A lot of information of Paeoniae Radix Alba and Paeoniae Radix Rubra can be provided by FT-IR spectra method and 2D-IR correlation spectra method which can testify that the content and structure of substance in Paeoniae Radix Alba and Paeoniae Radix Rubra were different and can be used to analyze and distinguish Paeoniae Radix Alba and Paeoniae Radix Rubrapreliminarily which can make a good foundation for further research.