Chemical Study Of Natural Red Tea

In this study, our objective is to study the bioactive flavonoids from a new tea cultivar-Zijuan tea. The ZTE1, ZTE2and ZTE3were extracted by methanol, defatted by diethyl ester and chloroform and purified by Amberlite XAD-7HP chromatography. The contents of anthocyanins (cyanidin-3-O-β-glucoside equivalent) in ZTE1and ZTE2were5.1±0.1and17.1±0.4mg/g and ZTE3was not detected. The contents of total polyphenol (catechol equivalent) in ZTE1, ZTE2and ZTE3were1.65±0.27,0.74±0.21,0.98±0.29mg/mg, respectively.The antioxidant activities of the three extracts were evaluated by using DPPH, ABTS, FRAP and linoleic acid radical model system. The DPPH radical scavenging activity of three extracts were higher than vitamin E and BHT, and their IC50were10.86,15.53,8.77μg/mL, respectively. The ABTS radical scavenging activity were higher than vitamin E and BHT, IC50were4.61,5.48,3.58μg/mL, respectively. The FRAP antioxidant capacity were higher than BHT, ZTE1was higher than vitamin Cand BHA. The linoleic acid radical inhibiting capacities were higher than vitamin C and Trolox.The whitening activities of the three extracts were evaluated with tyrosinase inhibitory assay. Single factor analysis and orthogonal experiment for the monophenolase and diophenolase activity of tyosinase were adopted to obtain the optimal conditions The results showed that the optimal conditions were as follows:L-tryosine,10.0mmol/L; tryosinase,0.30g/mL; reaction time,15min; reaction temperature,30℃and catechol,7.5mmol/L, tryosinase,0.035g/mL; reaction time,15min; reaction temperature,15℃. The ZTE1had the strongest inhibitory effect for both of the monophenolase and diophenolase. Their IC50were6.85×10-4,8.21×10-4,16.29×10-4g/mL and6.37×10-4,7.62×10-4,13.53×10-4g/mL, respectively.The compounds of AN-1, AN-2, AN-3and AN-4were isolated by Silica gel60C18chromatography. Their structures were characterized as delphinidin-3-O-β-galactoside, cyanidin-3-O-β-galactoside, delphinidin-3-O-β-D-(6-(E)-p-coumaroyl)galactopyranoside and cyanidin-3-O-β-D-(6-(E)-p-coumaroyl)galactopyranoside by a combination of HPLC, LC-ESI/MS,1H and13C NMR spectrometry and HR-TOF-MS. Four compounds characterized in this study were found in Zijuan tea for the first time.The antioxidant activities of AN-3and AN-4were evaluated using DPPH and FRAP method. The DPPH radical scavenging activities of AN-3andAN-4were higher than BHT, IC50were26.38and29.79μg/mL, respectively. The FRAP antioxidant capacities of them were higher than vitamin E and BHT. Our results wolud provide the scientific data for the further research and usage of Zijuan tea.