Colour and Flavour Characteristics of Made Tea

Antimicrobial activities of tocklai vegetative tea clones

Thirty-one Tocklai vegetative (TV) tea clones contained caffeine and total catechin 44.39 and 227.55 mg/g dry weight of leaves, respectively. The (-)-epigallocatechin gallate (EGCG) was the most abundant (109.60 mg/g) followed by -(-)-epigallocatechin (EGC, 44.54 mg/g), (-)-epicatechin gallate (ECG, 41.74 mg/g), (-)-epicatechin (EC, 27.42 mg/g) and +catechin (4.25 mg/g). Total catechins were highest in TV 20 (509.7 mg/g) and lowest in TV 6 (71.7 mg/g). The tea clones that contain high level of total catechin exhibited the strongest antimicrobial activity. Among caffeine and flavanol compounds, theaflavins (TF) present in black tea possess a similar antimicrobial potency as EC present in fresh leaves, and that the conversion of catechins to TF during fermentation in making black tea tends to alter their antimicrobial activities. The bioactive molecules other than catechins present in tea leaves may also contribute towards antimicrobial activity.

Black tea is a powerful chemopreventor of reactive oxygen and nitrogen species: comparison with its individual catechin constituents and green tea

Production of black tea [BT] results in biotransformation of catechins of green tea [GT] to theaflavins and thearubigins. BT was found to be more efficient than GT and its individual catechin constituents in proportionate amounts in abrogating production of NO and O2(-) in activated murine peritoneal macrophages. In a reconstitution system of BT that is free of all catechins, stepwise addition of catechins showed that though all the constituents contributed to the overall effect of BT, theaflavin was the most powerful in abrogating NO production. RT-PCR analysis also showed theaflavin to be the most important constituent in down-regulating synthesis of iNOS. Clearly, BT containing theaflavin is an excellent chemopreventor against reactive oxygen and nitrogen species.

Thermospray-LC-MS analysis of various groups of polyphenols in tea. II: Chlorogenic acids, theaflavins and thearubigins

An account is given of the application of thermospray LC-MS in the analysis of caffeoyl- and p-coumaroylquinic acids, theaflavins and thearubigins in black tea. All compounds, except for the thearubigens, could be detected as the pseudo-molecular ion [M + H]+. In addition to [M + H]+, other species such as adducts with sodium, ammonium and potassium, as well as solvent clusters were observed. The formation of those adducts depended upon on the structure of the compound. A fragmentation of chlorogenic acids occurred at elevated temperatures yielding the constituents of the molecules (caffeic, p-coumaric and quinic acids).