Differentiation of the root of Cultivated Ginseng, Mountain Cultivated Ginseng and Mountain Wild Ginseng using FT-IR and two-dimensional correlation IR spectroscopy
Introduction
Ginseng, the root and rhizome of Panax ginseng C.A. Meyer, is one of the most widely used herbal medicines in the world, which benefits to general health, including positive effects on the endocrine, cardiovascular, immune, and central nervous systems, prevention of fatigue, oxidative damage, mutagenicity and cancer prevention [1], [2]. Based on the grown environment and the cultivate method, the commercial trade ginseng is classified into three grades of ginseng, Cultivated Ginseng (CG), Mountain Cultivated Ginseng (MCG) and Mountain Wild Ginseng (MWG), CG is cultivated artificially in forms and contributes the major quantity of ginseng in the current market, MWG grows in the natural environments, vegetating in the deep mountains and MCG can be considered as mimicry wild ginseng which is seeded in plan but transferred to and grown up in the forest and mountain[3]. Normally CG is harvested after 5–6 years cultivation, MCG is collected ant the ages of 10–20 years or more, and MWG of exact ages is not clear, but judged by the morphologies. Although the same Latin name, Radix Ginseng, is given for all the above mentioned ginseng, their disparity in value on the market is remarkably great, almost more thousands times among of them, as the eastern people believe that consumption of MWG of more than hundred ages can elongate life of human being. Persistent harvest of long-lived, slow-maturing species can have negative impacts on population growth rates [4]. Especially MWG became very rare as the amounts decreasing significantly during recent decades. For protecting MWG populations in China, the laws have been promulgated that picking MWG is not permitted. Despite of not real wild ginseng, transplanting ginseng in the mountain and grown in the forest natural environment became the second choice to chase for the big marketing of wild ginseng. The traditional approach of distinguishing the CG, MCG and MWG was to check their morphological difference from each other or count their remaining stem scar on the rhizomes, by experienced ginseng farmer or handicraftsman, which was obviously depended on the subjective judgment. The modern analytical technologies such as thin-layer chromatography (TLC) [5], high-performance liquid chromatography (HPLC) [6], and tandem instrumentation of liquid chromatography with mass spectrometry (LC/MS) [7] etc. were applied to identify and differentiate the ginseng crude drug and products based on the chemical components such as ginsenosides.
But unfortunately, all of these methods have the disadvantage of a time-consuming sample procedure and the destruction of the hundred milligram sample, which is extremely expensive, especially for MWG. Even more, CG, MCG and MWG are quite similar in their chemical ingredients of ginsenosides and could not be discriminated from each other by the chromatographic methods. So a quick, applicable and non-destructive analysis method is urged for authentication of CG, MCG and MWG at this moment.
Fourier transform infrared spectroscopy (FT-IR) has been most widely used and well established tools for structure elucidation and quality control in various industries application. This technique has also gradually entered into the identification and classification of natural products like herbal [8], microorganism [9] and food [10] etc. The obvious advantage of FT-IR application to discriminate different natural products was not only effective and specificity, but rapid and non-separative. Combining the processing of chemometrics such as derivative IR spectra, the derivative of the spectrum slope which can enhance the spectral resolution, and two-dimensional correlation infrared spectroscopy(2D-IR), it consists of multi-steps infrared macro-fingerprint analysis to tackle the solution of herbal production identification. Sun’s group [11], [12], [13], [14], [15] had comprehensively researched in this area and proved FT-IR was one of useful and powerful tools to conduct out the non-destructive identification of expensive and precious objects. In this paper, we will discuss the method established by FT-IR, two secondary derivative IR spectroscopy and 2D-IR, as well as hierarchical cluster analysis to discriminate CG, MCG and MWG.
Section snippets
Apparatus
Spectrum GX Fourier transform-infrared spectroscopy (FT-IR) spectrometer (Perkin-Elmer), equipped with a DTGS detector. IR spectra were recorded from an accumulation of 32 scans in 4000–400 cm−1 range with a resolution of 4 cm−1. Programmable temperature controller (Model 50-886, Love Control Corporation).
Samples
Six CG, nine MCG and eleven MWG were purchased and obtained from ginseng companies of Xinbin and Huairen, Liaoning province, China; and all ginseng samples were identified by Dr. Hong Xu,
IR spectra analysis
The IR spectra of Mountain Wild Ginseng (MWG), Mountain Cultivated Ginseng (MCG) and Cultivated Ginseng (CG) under a room temperature is shown in Fig. 1. As a kind of macro-fingerprinting feathers of natural product complex, several characters can be extracted, such as, the strongest peak at 3420 cm−1 belonged to the stretching vibration of O–H groups, the peak at 2928 cm−1 assigned to the stretching vibration of –CH2– groups, the peak at 1740 cm−1 is due to the stretching vibration of CO groups
Conclusion
By using FT-IR, secondary derivative spectra and 2D-IR, as well as hierarchical cluster analysis, the discrimination of Cultivated Ginseng, Mountain Cultivated Ginseng and Mountain Wild Ginseng can be successfully found. The findings indicated that the relative content of starch in the CG was more than that in MCG and MWG, and the relative content of calcium oxalate and lipids in MWG were greater than that in CG and MCG, and the relative content of fatty acid in MCG was more than that in CG and
Acknowledgements
This work was financially supported by the Science & Technology Commission of Shanghai Municipality (04DZ19834), China. The authors thank Professor Jia-Xun Tao, Professor Qun Zhou and Dr. Hong-Xia Liu for their kind assistances.
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