Metabolic Mechanism and Bioactivity of Tea Catechins
| Autor: | Meei-Ju Yang, 楊美珠 |
|---|---|
| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 107 Catechins and its polymers offer various health benefits. Therefore, it is very important to realize catechin metabolic process and its physiological activity during manufacturing and storage process. This result will support for future various functional tea production. Catechin is unstable and easily oxidized in water solution. Non-enzymatic browning of tea was due to photooxidation, temperature and pH variation. Hence catechin chemical transformation at different environmental conditions is an important issue in tea drink manufacture. In this study, first, we try to figure out the change of catechin under blue light irradiation in alkaline solution by chromatography and mass spectrometry techniques. Catechin is colorless in water solution. However, it was turn into yellow color under blue light irradiation in alkaline condition. The yellow substance was characterized as catechin dimer (proanthocyanidin) and it can be prevented by ascorbic acid addition. It showed that ascorbic acid will inhibit catechin photooxidation. A superoxide anion was produced through catechin photooxidation under blue light irradiation in alkaline condition. This free radical can cause inactivation of multidrug-resistant Acinetobacter baumannii and support as solution for environmental microbial safety. Furthermore, different fermented tea from the same resource of tea leaves was produced and was analyzed by chromatography and mass spectrometry techniques to understand correlation of catechin metabolic pathway during different fermented process. As the degree of fermentation (oxidation) increases, metabolic reaction of catechin was increased and catechin was decreased followed by increasing of theasinensins (TSB and TSC), theaflavins (TF and TF3G) and gallic acid. Non-fermented tea (green tea) and semi-fermented tea (pouchong and oolong tea) have high DPPH scavenging effect, reducing power and ABTS free radical scavenging ability, owing to high catechin concentration. Completely fermented tea (black tea) has high ferrous ion chelating ability because of high theasinensins, theaflavin and gallic acid concentration. Forty-six compounds were characterized for three different fermented tea by analytical liquid chromatograph tandem mass spectrometer with collision-induced dissociation (CID). It showed that variation of molecular composition after tea fermentation. Catechins and flavonol aglycones were significantly decreased followed by formation of organic acid, theasinensins and theaflavin. In addition, a lot amount of catechin dimers were detected in green tea, and decreasing when fermentation. Chemical composition was analyzed from different age of strip type partial fermented tea to explore the effects of storage on the metabolism of catechins. The mechanism of tea inhibited inflammatory response was discussed by immune response was stimulated by foreign substances lipopolysaccharide (LPS) in macrophages RAW 264.7 and trigger nitric oxide (NO) generate. As the results, as the time go by, total polyphenol, total catechin, total catechin dimer and total theasinensin were reduced without theaflavin production. It showed that metabolic mechanism is difference between manufacture process and tea storage. The phenomenon of pH value first drops and then rise of tea was cause by combination of catechin metabolic products “gallic acid” and other organic acids change. Anti-inflammatory ability of tea was enhanced with rising of storage time and test dose. The bioactivity test of tea storage time indicating a positive correlation between metabolic compounds: gallic acid, pyrogallol, caffeoyl tartaric acid derivative, quinine derivative, bayberry flavonoid glycoside, kaempferol and ellagic acid and anti-inflammatory ability. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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