Inhibition of ACE activity by the main components of Gabaron tea in vitro
Components Concentration (mM) ACE activity (%) Inhibition (%)
GABA 40 10.53 89.47
Alanine 40 23.08 76.92
Theanine 40 34 64.00
GHBa 40 42 51 57 49
Source: Lin, Z. and Omori, M. 2001. Effects of Gabaron tea components on angiotensin I-converting enzyme activity in rat . In Proceedings of the 2001 International Conference on O-CHA(tea) Culture and Science, Shizuoka, Japan, 81-84 . With permission . a GHB = Y-Hydroxybutyric acid .
investigated for comparison . Using 28 green teas and 28 GABA teas as material, moisture content, Hunter L, a, and b values, phenolic compounds, and amino acids, including GABA, fatty acids, and ascorbic acid, were determined The results showed that moisture, total free amino acids, crude fat, Hunter L value, total nitrogen, free fatty acids, and reducing sugar did not differ significantly between the two . The major difference was that GABA tea had higher GABA, alanine, ammonia, lysine, leucine, isoleucine, and Hunter a and b values, while green tea had higher glutamic acid, aspartic acid, phenylalanine, total catechins, and ascorbic acid content (p < 0 . 05) . 130
For the animal test, high-dose GABA (300 mg/100 g) and low-dose GABA (150 mg/100 g) of Taiwan GABA teas together with green tea were made by Chin-Shin Oolong as experimental samples and fed to the spontaneously hypertensive rats (SHR) and compared with the high and low doses of pure GABA solution and water as control . The blood pressure, body weight, serum GABA, and serum lipids (including total cholesterol, triacylglycerol, and high-density lipoprotein (HDL) and low-density lipo-protein (LDL) cholesterols of SHR were measured periodically The results showed that after 12 weeks of feeding, the blood pressure of SHR fed with either high-dose or low-dose GABA tea solution was reduced significantly, and the effectiveness was greater than those with pure GABA and green tea solutions (table 4 . 6) .
From the results for the effect of feeding GABA tea on the serum triacyl-glycerol, cholesterol, LDL-C, HDL-C, GABA, and tetrabutylammonium hydrogen sulfate (TBAS) of SHR (table 4 .7), the effect of GABA tea solution on reducing serum lipids was the same as that of green tea As the blood pressure decreased, serum GABA of SHR increased However, there was no significant difference in serum GABA of SHR fed with a high or low dose of GABA for both pure GABA and GABA tea . In terms of triacylglycerol, cholesterol, LDL-C, and HDL-C, the reading for the control (drinking water) had no significant change, while for all other groups the readings significantly decreased Thus, these studies indicated that GABA tea extract indeed has good biological functions, especially reduction of blood pressure and serum lipids for SHR .
Furthermore, when extending the feeding period up to 82 weeks (age of 95 weeks), only SHR fed with either high-dose or low-dose GABA tea infusion were all alive (figure 4 . 5) . The number of survivors in the control, green tea, and low-dosage pure GABA solution-treated groups decreased to 50, 57.14, and 66 .7%, respectively. Clearly, the survival rate of the GABA tea-treated group at 100% contrasted strongly with those of the other groups Consequently, the largest survival benefit was conferred by the GABA tea-treated group, with the rest in the following order: pure GABA solution > green tea > control group
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