Determination of Phenolic and Antioxidant Properties in Tea and Spent Tea Under Various Extraction Method and Determination of Catechins, Caffeine and Gallic Acid by HPLC

Abstract

Tea (Camellia sinensis L.) contain high phenolic compounds and antioxidant elements, while spent teas originating as the main byproduct of beverage tea manufacturestill contain some level of antioxidant elements. The purpose of the present study is to compare the effect of different extraction condition and to determine the chemical compound present in black tea (BT), oolong tea (OT), green tea (GT), spent black tea (SBT), spent oolong tea (SOT) and spent green tea (SGT). Theextraction experiment were carried out by the conventional solid-liquid method, using boiling water (100oC) and 50% ethanol concentration, with extraction period of 5 minutes. The influence of these extraction methods on the content of total phenolic compounds and antioxidant activities of the extracts were evaluated. Flavanoid, gallic acid, caffeine and four catechins (catechin (C), gallocatechin (GCG), epicatechin (EC) and epigallocatechin (EGC)) were found in all of the extracts and were quantified by utilizing High Performance Liquid Chromatography (HPLC) analysis tool. GT extraction using 50% ethanol concentration was found to be the most suitable method to produce an extract with high content of phenolic compounds ( 186.83 mg GAE/100 g tea) and high antioxidant activities (FRAP of 3814.29 μmol Fe(II)/g), simultaneously. The results shown that GT had higher total flavanoids value at 347.67 mg CEQ/g followed by OT (295.00 mg CEQ/g) and than the BT (187.33 mg CEQ/g). The analytical HPLC results obtained also indicated that GT contained higher amount of catechins than OT, BT, SGT, SOT and SBT due to fermentation process during the tea manufacturing, which reduces the levels of catechin significantly. All four catechins were detected in GT. However, epicatechin, and gallocatecin gallate are the major catechin present in SGT.