Bioactive components and antioxidant properties of γ-aminobutyric acid (GABA) tea leaves

• Published in: Food science & technology 2012-04, Vol.46 (1), p.64-70
• Main Authors: Lin, Sheng-Dun, Mau, Jeng-Leun, Hsu, Ching-An
• Format: Article
• Language: English
• Subjects: Antioxidant property; Biological and medical sciences; Catechin; Coffee, tea and other stimulative beverage industries; Food industries; Fundamental and applied biological sciences. Psychology; GABA tea; Theanine; γ-Aminobutyric acid
• ISSN: 0023-6438; 1096-1127
• DOI: 10.1016/j.lwt.2011.10.025

Various ethanolic concentrations (0–95%, v/v) and temperatures (25–95 °C) were used to extract γ-aminobutyric acid (GABA) tea leaves. Extraction yields, and contents of total phenols, various catechins, GABA, theanine, and antioxidant properties of extracts were determined. The 50% (v/v) ethanol at 50–95 °C gave higher yields (32.05–32.56 g dried extract/100 g dried tea leaves). The bioactive components and antioxidant properties of extracts were affected by the ethanolic concentrations and temperatures. Among catechins, epigallocatechin gallate was the main catechin in all extracts, followed by epigallocatechin, epicatechin, epicatechin gallate, gallocatechin and gallocatechin gallate. The 50–75% (v/v) ethanol at 75–95 °C gave higher contents of ester type (102.92–104.54 mg/g extract) and non-ester type (61.75–63.55 mg/g extract) catechins. Water at 50–75 °C gave higher GABA and theanine contents and higher chelating ability of extracts. The 75% (v/v) ethanol at 25–75 °C gave higher scavenging ability and reducing power of extracts. Based on dried tea extracts or leaves results obtained, the optimal extraction conditions to maintain the total contents of various catechins, GABA and theanine in the maximum level were 50% ethanol (v/v) and 75–95 °C. ► The 50% ethanol at 50–95 °C gave higher extraction yield. ► The 50–75% ethanol at 75–95 °C gave higher total phenols and catechins of extracts. ► Water at 50–75 °C gave higher GABA and theanine contents of extracts. ► Water extracts have the higher chelating ability on ferrous ions in all extracts. ► The 75% ethanol extract gave the higher scavenging ability on DPPH radicals.