Determination of methylated catechins in Sichuan green tea,yellow tea, dark tea,black tea and green tea by high performance liquid chromatography-diode array detection method

EGCG3″Me contents of 48 tea samples in green tea,yellow tea,dark tea tea,black tea and oolong tea from 23 enterprises of Ya’an,Chengdu,Leshan,Yibin and Mianyang City in Sichuan Province were comparative studied by high performance liquid chromatography-diode array detection(HPLC-DAD).The results showed that EGCG3″Me content in oolong tea was highest,ranged from 3.14 to 6.08 mg/g,the mean value was 4.40 mg/g;EGCG3″Me content in dark tea ranged from 0 to 1.72 mg/g,the mean value was 0.35 mg/g;EGCG3″Me contents in green tea and yellow tea were lower,green tea ranged from 0 to 0.39 mg/g,the mean value was 0.10 mg/g;yellow tea ranged from 0 to 0.09 mg/g,the mean value was 0.05 mg/g;black tea do not contain detectable EGCG3″Me.The reasons for the differences were the varieties,plucking standards and processing methods of fresh leaves. It was suggested that allergic people should drink oolong tea properly.