Extraction and separation of tea polyphenols and caffeine from tea leaves by mechanochemical pretreatment

Abstract

Mechanochemical pretreatment (MCPT) was applied to the extraction and separation of tea polyphenols (TP) and caffeine from tea leaves. Tea leaves were treated by mechanical activation with presence of Na2CO3 (MC) for 75 s. One gram of obtained powder was taken for extraction and separation to obtain the sample of MC (A) fraction and MC (B) fraction. According to caffeine and epigallocatechin gallate (EGCG) (a representative component of TP) yields in the sample, the optimum MCPT extraction conditions were as follows: 15% (w/w) Na2CO3 during milling, extracting caffeine with 40 mL 75% (v/v) ethanol and EGCG with 40 ml water at room temperature. Under these conditions, the caffeine EGCG yield in MC (A) fraction was 0.51 mg/g, and the EGCG yield in MC (B) fraction was 1.32 mg/g, with EGCG/caffeine ratio of 2.38. Compared with extraction with mechanical activation without presence of Na2CO3 (M) and traditional extraction with no mechanical activation (CON), the MC extraction had obvious advantages. In conclusion, the MCPT is an effective method for the extraction and separation of TP and caffeine from tea leaves.