霍山石斛、铁皮石斛与河南石斛花茶多级红外光谱快速鉴定研究

The Discrimination of the Flower Tea of Dendrobium Huoshanense, Dendrobium Officinale and Dendrobium Henanense by a Multi-Step FTIR Method

将石斛的鲜花干制成花茶,作为保健饮料日渐为市场接受。由于口感、药理活性与产量的差异,不同来源的石斛花茶,价格差异显著,其中以霍山石斛花茶价格最高。在经济利益驱使下,以价格较低的铁皮石斛、河南石斛花茶冒充霍山石斛花茶时有发生,急需构建霍山石斛花茶与铁皮石斛、河南石斛花茶的鉴定方法。建立一种快速鉴定霍山石斛、铁皮石斛、河南石斛花茶多级红外光谱方法。收集不同企业生产的不同批次的霍山石斛、铁皮石斛、河南石斛花茶样品,利用衰减全反射测定4 000~400 cm^-1范围内一维红外光谱;一维红外光谱通过数据变换获得二阶导数光谱;利用温度微扰获得二维红外光谱。分析一维红外光谱、二阶导数光谱、二维红外光谱获得三种石斛花茶区别。结果显示,三种石斛花茶的一维红外光谱非常相似,很难从外观上看出三者的区别。分析一维红外光谱吸收峰发现,霍山石斛花茶在1 398 cm^-1有特征峰,铁皮石斛花茶在1 542 cm^-1有特征峰,河南石斛花茶在1 610, 1 332,811, 703和603cm^-1等处有特征峰;二阶导数处理能明显的提高光谱分辨率、增加光谱灵敏度。三种石斛花茶在1 800~600cm^-1的二阶导数光谱上,可以观察到明显差异:在1 750~1 690 cm^-1区间,相对铁皮石斛与河南石斛,霍山石斛花茶二阶导数光谱呈明显"M"形;在1 140~1 080 cm^-1区间,霍山石斛与河南石斛二阶导数光谱呈"W"型,铁皮石斛呈不规则形;在1 000~930cm^-1区间,霍山石斛花茶二阶导数光谱为"M"形,铁皮石斛与河南石斛花茶呈"W"形;二维红外光谱显示,在1 230~1 130 cm^-1区间,霍山石斛有5个分别位于1 134, 1 155, 1 182, 1 196和1 211cm^-1的自动峰,铁皮石斛有2个分别位于1 186和1 210cm^-1的自动峰,河南石斛有3个自动峰,位于1 186, 1 197和1 209cm^-1。霍山石斛在1 230~1 130 cm^-1区间存在正相关峰(1 182和1 210cm^-1)、正相关峰(1 135和1 181cm^-1)、负相关峰(1 197, 1 155 cm^-1),而河南石斛和铁皮石斛在该区间没有明显的相关峰。根据一维、二阶导数和温度微扰二维红外光谱可以快速鉴别霍山石斛、铁皮石斛与河南石斛花茶。

The flower tea dried from the flowers of Dendrobium plants was becoming a kind of more and more favorable drink these years. Among them, the flower tea of Dendrobium huoshanense was the most expensive because of its lower yield, better mouthfeel and relative higher pharmaceutical activity comparing with other Dendrobium flower teas. Thus, the flower tea of D. huoshanense was often masqueraded by the cheaper Dendrobium flower tea, such as D. officinale and D. henanense, due to the economic interests. In this paper, a multi-step FTIR method was established to rapidly discriminate the flower tea of Dendrobium huoshanense, Dendrobium officinale and Dendrobium henanese. Different Dendrobium flower tea samples were collected from different manufacturers in July, 2018, then their Attenuated Total Reflection Flouriertransformed Infrared(ATR-FTIR) Spectroscopy and the two-dimensional correlation infrared(2D COS IR) spectra perturbed by temperatures were detected in the range of 4 000~400 cm^-1. The second derivative infrared(SD-IR) spectra were calculated from their corresponding ATR-FTIR spectroscopy. The results showed that, although direct discrimination of the Dendrobium flower tea by FTIR spectrum is quite difficult, different intensities and peak positions could be found by analysis of their ATR-FTIR files. The flower tea of D. huoshanese and D. officinale had characteristic peaks at 1 398 and 1 542 cm^-1, respectively, while D. henanese obtained characteristic peaks at 1 610, 1 332, 811, 703 and 603 cm^-1. Treatment by second derivative can improve the spectral resolution and sensitive remarkably and direct discrimination can be observed in SD-IR spectrum. The three kinds of Dendrobium flower tea could be discriminated by the "M" shape of D. huoshanese in the range of 1 750~1 690 cm^-1, by the "W" shape of D. huoshanese and D. henanese, the irregular shape of D. officinale in the range of 1 140~1 080 cm^-1, and by the "M" shape of D. huoshanese while the "W" shape of D. officinale and D. henanese in the range of 1 000~930 cm^-1. As for the 2D COS IR spectra, in the range of 1 230~1 130 cm^-1, the three kinds of flower tea could be discriminated by the auto-peaks at 1 134, 1 155, 1 182, 1 196 and 1 211 cm^-1 for D. huoshanese, at 1 186 and 1 210 cm^-1 for D. officinale, at 1 186 and 1 210 cm^-1 for D. henanese. In addition, There were two positive-correlation cross-peaks at 1 182 and 1 210 cm^-1, at 1 135 and 1 181 cm^-1, and one negative-correlation cross-peak at 1 197 and 1 155 cm^-1 in the 2D COS IR spectrum of the flower tea of D. huoshanese, while no cross-peak was observed in the 2D COS IR spectrum of the flower tea of D. officinale and D. henanese in the range of 1 230~1 130 cm^-1. The multi-step FTIR technology involving ATR-FTIR, SD-IR and 2D COS IR could be used to rapidly identify the flower tea of D. huoshanese, D. officinale and D. henanese.