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Major chemical constituents and Bioactive Functions of Taiwan GABA Tea
|關鍵字:||ABA tea;佳葉龍茶;GABA;catechins;physicochemical analyses;Antioxidant;blood pressure;blood lipids;heart beat;γ-胺基丁酸;兒茶素;抗氧化;血壓;血脂;心跳||出版社:||食品暨應用生物科技學系||摘要:||
佳葉龍茶為台灣之一種新興茶。為了瞭解台灣佳葉龍茶之主要化學成分及其生理功效，本研究分四階段探討。第一階段著重於台灣茶區產製佳葉龍茶之物理化學的探討。第二階段主要探討不同品種、產區與產季對台灣佳葉龍茶之主要化學成分，特別是γ-胺基丁酸 (γ-aminobutyric acid，GABA)含量的影響。第三階段主要在探討台灣茶區產製的佳葉龍茶之抗氧化成分含量，並進一步評估其抗氧化能力。第四階段係以動物試驗進行佳葉龍茶之降血壓與其他生理功效及有效劑量的探討。
第一階段，以收集與分析之56個春夏兩季茶樣 (28種綠茶與28種佳葉龍茶)，進行各項 (水分、Hunter L, a, b值、酚類化合物、胺基酸 (含GABA)、脂肪酸及抗壞血酸) 物理化學分析，以比較綠茶與佳葉龍茶成分之差異。結果得知，綠茶與佳葉龍茶兩者之水分含量、茶湯亮度Hunter L值、總游離胺基酸、總氮量、粗脂肪及所有的脂肪酸等均無顯著差異 (p > 0.05)。佳葉龍茶之茶湯的Hunter a與b值顯著高於綠茶，抗壞血酸及還原糖則顯著低於綠茶 (p < 0.05)。總多元酚中epicatechin (EC) 及epigallocatechin gallate (EGCG) 之含量顯著低於綠茶 (p < 0.05)，兩種茶之總兒茶素並無顯著差異 (p > 0.05)。另一方面，佳葉龍茶之GABA、丙胺酸、氨、離胺酸、白胺酸及異白胺酸等皆顯著高於綠茶，但麩胺酸、天門冬酸及苯丙胺酸則較低，茶胺酸、色胺酸及甲硫胺酸含量在佳葉龍茶與綠茶之間無顯著差異 (p > 0.05)。
第二階段為探討不同品種、產區與產季對台灣佳葉龍茶之主要物理化學成分，特別是GABA含量的影響，以28個佳葉龍茶為茶樣，利用物理化學分析不同品種 (四季春、青心烏龍、台茶12與13號)、產區 (桃竹苗、名間、鹿谷與嘉義) 及產季 (春、夏) 對所製造的佳葉龍茶之GABA、游離胺基酸、兒茶素類、咖啡因、總氮、粗脂肪、還原糖、抗壞血酸等成分及茶湯水色。結果顯示，不同季節產製之佳葉龍茶，除了抗壞血酸、Hunter a 值、還原糖和粗脂肪未達顯著水準差異外，總游離胺基酸及總氮量皆以春茶明顯較高於夏茶；不同產區所產製之佳葉龍茶，除總游離胺基酸和總氮未達顯著水準差異外，嘉義茶區所產製的佳葉龍茶，其抗壞血酸和粗脂肪明顯較其它茶區為高，而且Hunter a及b值也特別高；至於不同品種，除抗壞血酸及還原糖有些微差異外，其餘皆未達顯著水準差異，這顯示不同品種之一般基本成份差異很小。不同季節產製之佳葉龍茶，EC、EGCG、ECG及咖啡因達顯著水準差異，而其餘GC、EGC、C及總兒茶素則未達顯著水準差異。四個茶區產製之佳葉龍茶的EC、ECG及EGCG含量皆無顯著差異，總兒茶素含量則以嘉義茶區明顯高於其他三個茶區，GC及咖啡因則以名間顯著高於其他茶區。至於不同品種，大部份兒茶素類皆無差異，只有四季春之EGCG及ECG這兩種酯型兒茶素含量明顯高於其它三品種。不同產區對胺基酸之影響遠較不同季節與不同品種大，這極可能與不同產區因海拔高度差異甚大有關。但不論不同季節或產區或品種，所製佳葉龍茶之GABA含量均可達商品化 (150 mg/100 g) 水準之上，且以春季、嘉義和鹿谷的台茶12號產製者，可高達200 mg以上。
第三階段在於瞭解台灣茶區產製的佳葉龍茶茶湯之抗氧化成分與其抗氧化能力，以20個春夏兩季產製之佳葉龍茶茶湯利用物化分析探討不同品種、季節、產區之茶菁所製造的佳葉龍茶之抗氧化性成分 (包括GABA、酚類化合物、主要胺基酸及抗壞血酸)，並進一步評估其抗氧化能力 (清除超氧陰離子、螯合亞鐵離子、捕捉DPPH及羥基自由基能力)。另以20個相同產製條件的綠茶作為對照。結果：綠茶之抗壞血酸、茶湯亮度Hunter L 值、天門冬酸、麩胺酸、茶胺酸、總兒茶素、EC及EGCG等含量較高；茶湯的Hunter a 與 b 值、GABA及丙胺酸則以佳葉龍茶的含量較高。佳葉龍茶之螯合亞鐵離子能力 (90.92 %) 顯著高於綠茶 (80.24 %)，但清除超氧陰離子、捕捉羥基自由基與DPPH自由基能力上並無不同。此外，佳葉龍茶水萃取物抑制50 % (EC50) 自由基產生的能力之有效劑量分析結果顯示，佳葉龍茶茶湯之螯合亞鐵離子能力、清除超氧陰離子、捕捉羥基自由基與DPPH 等作用的EC50濃度分別為1.10、2.03、2. 28及24.0 μg/ml，綠茶則分別是1.31、2.00、2.4.及23.8 μg/ml。此結果顯示，佳葉龍茶茶湯的抗氧性質在螯合亞鐵離子能力上優於綠茶，而清除超氧陰離子、捕捉羥基與DPPH自由基則與綠茶相同。以上結果得知，佳葉龍茶具有良好的抗氧特性，尤其以螯合亞鐵離子能力最為突出。
第四階段係以動物試驗進行佳葉龍茶之降血壓與其他生理功效及有效劑量的探討。以青心烏龍品種的茶菁分別製成高GABA含量 (300 mg/100g)、低GABA含量 (150 mg/100 g) 的佳葉龍茶與綠茶作為動物試驗之主要茶樣 (試驗組)，加上以相同劑量之純GABA水溶液當對照組，蒸餾水為控制組，探討佳葉龍茶之生理功效及其有效劑量。結果顯示，試驗前SHR的血壓、心跳、體重、攝食量、飲水量、血清GABA與血脂及脂質過氧化產物皆無組間差異。在餵食試驗12週後結果發現，不論高或低劑量的佳葉龍茶水萃取物都有降低SHR高血壓的作用，且較單獨使用GABA水溶液或綠茶水萃取物的效果好。降血脂之功效則與綠茶水萃取物相同。結果顯示，SHR血壓下降之程度與血清GABA值呈正相關性。但六組的SHR之食慾則在餵食12週後皆有下降現象。因此本研究結果顯示，佳葉龍茶水萃取物具有降低SHR高血壓與改善血脂的作用。
GABA (γ-aminobutyric acid) tea is a new type of tea in Taiwan. In order to investigate the major physiochemical constituents and bioactive functions of Taiwan GABA tea, the present study is divided into four parts. The first part focused on the comparison of bioactive components in GABA tea and green tea produced in Taiwan. The second part investigated the difference in chemical components of Taiwan GABA tea with different varieties, producing areas and seasons, especially the GABA contents. The third part focused on the contents of antioxidants in GABA tea with different production areas in Taiwan and further evaluated its antioxidant ability. The fourth part examined the lowering blood pressure ability, other physiological efficiency and effective dose of GABA tea by animal''s test.
To investigate the bioactive components of GABA tea as compared with green tea produced in Taiwan, the moisture content, Hunter L, a and b values, phenolic compounds, amino acids, GABA, fatty acids and ascorbic acid of totally 56 tea samples (28 green tea and 28 GABA tea) 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 GABA tea and green tea. However, GABA tea had higher Hunter a and b values, while green tea had higher total catechin and ascorbic acid contents (p < 0.05). Of major catechins, epicatechin and epigallocatechin gallate were found lower in GABA tea than in green tea. For free amino acids, GABA, alanine, ammonia, lysine, leucine and isoleucine were found significantly higher in GABA tea, while the glutamic acid, aspartic acid, and phenylalanine were higher in green tea (p < 0.05). Theanine, tryptophan, valine, threonine and methionine were not different between the two kinds of tea.
The main goal of the second part of the study is to investigate the effects of varieties (Shy-Jih Chue, SJchue; Chin Shin Oolong, CSOolong; Taiwan Tea Experiment Station 12 and 13, TTES 12 and 13), production areas (Min-Jian, Tao Chu Miao (TCM), Lugu and Jia-Yi) and seasons (spring and summer) on the chemical components of GABA tea, especially the GABA content. Twenty eight GABA tea samples were used and their GABA, free amino acids, catechins, caffeine, total nitrogen, crude fat, reducing sugar and ascorbic acid contents and Hunter L, a and b values were examined by physicochemical analyses. The results showed that the difference in the ascorbic acid, Hunter a value, reducing sugar and crude fat was not significant between two seasons while the contents of total free amino acids and total nitrogen in GABA tea made in spring was significantly higher than that in summer (p < 0.05). For GABA tea made in different production areas, the contents of ascorbic acid and crude fat and the Hunter a and b values were higher in Jia-Yi than in other areas. Among the different tea varieties, only ascorbic acid and crude fat were slightly different. It indicates that the difference in above-mentioned constituents in these four tea varieties was little. In terms of catechins and caffeine, the contents of EC, EGCG, ECG and caffeine in GABA tea made in the two seasons were significantly different (p < 0.05) except the gallocatechin (GC), (+)-catechin(C), EGC and total catechins. The amounts of EC, ECG and EGCG in GABA tea produced in four areas were not significantly different. The TC contents in GABA tea produced in Jia-Yi were the highest while the GC and caffeine contents were significantly higher in Min-Jian than in other areas (p < 0.05). Among the tea varieties, there was no significant difference in most catechins. Only the contents of two ester-type catechins, EGCG and ECG, in GABA tea of SJChue were significantly higher than those of other three varieties (p < 0.05). For amino acids, the influence of production area was far more than that of season and tea variety. However, the GABA contents in all GABA tea by different variety in different season and production area reached the commercial level (150 mg GABA/100 g made tea) and that in GABA tea made by TTES 12 in Jia-Yi and Lugu in spring were even above 200 mg per 100 g made tea.
The third part of the study mainly focused on the antioxidants of GABA tea produced in Taiwan and their antioxidative ability. Using 20 GABA teas and 20 green teas as materials, the contents of antioxidants (including GABA, phenols, major amino acids and ascorbic acid) in Taiwan GABA tea with different variety, season and production area were analyzed and the antioxidation ability (removal of superoxide anion, chelating ferrous ion, and scavenging DPPH and hydrodyl radicals) was further evaluated. The results showed that the contents of ascorbic acid, aspartic acid, glutamic acid, theanine, total catechins, EC and EGCG and Hunter L value were significantly higher in green tea than in GABA tea (p < 0.05) while the Hunter a and b values and alanine were lower in green tea than in GABA tea. The antioxidant ability tests showed that the chelating of ferrous capacity was found higher in GABA tea (90.92 %) than in green tea (80.24 %), but the abilities of scavenging DPPH and hydroxyl radicals and removal of superoxide anion were not significantly different between GABA tea and green tea. In addition, the concentrations required for 50 % effective concentration (EC50) for ferrous, superoxide anion, hydroxyl and DPPH radicals were 1.10, 2.03, 2.28 and 24.0 μg/ml, and green tea were 1.31, 2.00, 2.40 and 23.8 μg/ml, respectively. The antioxidative capacities of GABA tea decreased in the order of chelating ferrous anion > removal of superoxide anion radical > scavenging hydroxyl radical > scavenging DPPH radical. These results have shown that GABA tea extracts have antioxidative ability.
The fourth part of the study examined the ability of lowering down the blood pressure, other physiological efficiency and effective dose of GABA tea by animal test. High dose GABA (300 mg/100 g) and low dose GABA (150 mg/100 g) of Taiwan GABA tea together with green tea were made by CSOolong varieties as experimental samples. These samples were used to feed the spontaneously hypertension rats (SHR) and compared with the high and low doses of pure GABA solution (300 mg/100 g) and 150 mg/100 ) and water as control. The blood pressure, body weight, serum GABA and serum lipids (including total cholesterol, triglycerides, and HDL and LDL-cholesterols) of SHR were measured periodically. The results of the animal test in the first stage indicated that the blood pressure, heart beat, body weight, feeding, drinking, serum GABA, and lipids were not different significantly among the six groups of SHR. At the stage of 12th week, it was found that the blood pressure of SHR fed with high and low dose GABA tea infusion was decreased together with the increase of serum GABA of SHR. The effectiveness of reducing blood pressure of SHR by GABA tea infusion was higher than that by pure GABA solution and green tea infusion. The GABA tea infusion was also found the effectiveness of reducing serum lipids as same as green tea. Furthermore, the feed intake of six SHR groups was decreased after feeding for fifteen weeks and it results in weight-control.
It may say that GABA tea is almost the same as green tea in terms of the above-mentioned bioactive compounds. In addition, GABA tea contains a high level of GABA which has shown the affectness for the blood pressure and the nervous and cardiovascular systems of SHR. Overall, GABA tea is concluded as good as green tea in bioactivity.
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