HPLC Fingerprint Of Ziyang Green Tea Polyphenol Extracts

Shaanxi Ziyang Se-enriched tea is the national geographical indications protection products. It has not only the functional and nutritional effects of tea, as well as selenium supplyment effect. Thus, some shoddy and counterfeit phenomena often occur in the market, which bring adverse effect to regular tea consumption and export trade. Currently, the identification of tea quality is mainly determining some conventional physical and chemical indicators and some major characteristic components in tea, combining with sensory evaluation, which has some limitations and can not reflect the tea quality comprehensively and objectively. Tea chemical fingerprint means that characteristic chromatography and database of tea obtained by using some suitable processing technique and analysis method, which can make a quantifiable assessment of tea quality identification, and to make up for lack of sensory evaluation. It can be used to evaluate and control the quality of the tea and its extracts. In this experiment, we use Shaanxi Ziyang green tea as raw materials to establish an HPLC fingerprint of Ziyang green tea polyphenol extracts, and make similarity evaluation, with a view to provide strong security and quality control standards for reference in quality assessment, geographical indications and authenticity identification of Ziyang green tea and and its extracts. The main research results are as follows:(1) The technological conditions for extracting the polyphenols from Ziyang green tea were optimized. The optimum extraction conditions:solid-liquid ratio was1:25, ethanol concentration was50%, extraction temperature was80℃, and extraction time was20minutes. Under the optimal conditions, the relative extraction rate of tea polyphenols can be97.8%. The order of four factors effect on the tea polyphenols relative extraction yield:solid-liquid ratio> ethanol concentration> temperature> extraction time.(2) An HPLC analysis method was established to simultaneously quantification detecting ten polyphenol components in Ziyang green tea samples. The chromatographic separation was performed on an Agilent Zorbax SB-C18column (5μm,4.6mm×250mm) using methanol-0.1%trifluoroacetic acid solution (solvent A;5:95, v/v; pH2.28) and methanol (solvent B) as mobile phase at a flow rate of1mL/min. The gradient elution program was set as follows:0～10min,0%～19%B;10～20min,19%～22%B;20～30min,22%～28%B;30～35min,28%～35%B;35～40min,35%～35%B;40～50min,35%～65%B;50～60min,65%～0%B. The chromatogram was monitored at a wavelength of278nm during the experiment. The column temperature was maintained at30℃and the injection volume of each sample and standard solution was20μL. Under the optimal conditions, ten polyphenol components were successfully separated. The method was acceptable with high precision, good stability and repeatability, sufficient sensitivity, and high recovery rates. The contents of10polyphenol components in10batches of green tea sample from different plantations in Ziyang County were also determined. The results showed that the catechins were the dominant components in Ziyang green tea samples. EGCG was the major catechin monomer. The largest variation was found in the contents of CA and GCG in different batches of tea samples. These data suggested that the quality of the commercial Ziyang green tea could be successfully monitored by determining these contents in the samples.(3) The HPLC fingerprint of Ziyang green tea polyphenol extracts was established. Peak EGCG was chosen as the reference peak, and13peaks in the chromatograms were assigned as "common fingerprint peaks" to represent the characteristics of Ziyang green tea polyphenol extracs. Seven components were identified as GA, EGC, EGCG, CAF, EC, ECG, and GCG by comparing their retention time and UV spectrum with those of standard compounds. The results of methodological investigation showed that this fingerprint met the national standard of establishing traditional Chinese medicine fingerprint. The similarities of the10batches of Ziyang green tea samples were all more than0.900. The results above demonstrated that the established HPLC fingerprint method was stable and reliable, and can be successfully used to assess the quality, as well as to identify the geographical indication and authenticity of Ziyang green tea and its extracts.