**3.2 GABA, theanine, caffeine and EGCG content in a cup of tea**

Two separate brews of each tea were analysed in duplicate for GABA and theanine, and three separate brews were analysed in triplicate for caffeine and EGCG in order to determine both the difference in constituent content between the teas and also the consistency of constituent content between separate brews of the same tea. Given the greater degree of variability encountered with the measurement of the caffeine and EGCG content in different brews, triplicate measurements were undertaken. The relative amounts of GABA, theanine, caffeine and EGCG and differences in constituent content between the two types of tea are shown in **Table 1** expressed as mg per 200 mL of brewed tea from 5 g of dry tea leaf. Good reproducibility in the extraction of constituents was demonstrated with our preparation protocol. Both teas showed consistent quantified constituent content between separate brews of the same tea.


Representative reverse-phase HPLC chromatograms are shown in **Figures 2** and **3**.

## **Table 1.**

*Amount of GABA, theanine, caffeine and EGCG in separate brews of oolong tea.*

#### **Figure 2.**

*Representative reverse-phase HPLC chromatograms of GABA and theanine in (A) regular oolong, and (B) GABA-enriched oolong teas.*
