Green and white teas are subject to minimal oxidation, whereas oolong and black teas are allowed to partially and extensively oxidize as a result of fermentation, respectively, with the highest grade of oxidization in case of pu-erh. According to the processing of the raw leaves, the main types of tea are green, white, oolong, black, and pu-erh teas.
#Theine and caffeine free#
The dried leaves of tea shrub contain 1–2% theanine as free amino acid and up to 7–9% methylxanthines, with caffeine as the quantitatively (3–6%) and pharmacologically most significant compounds. Moreover, together with caffeine, L-theanine has a synergistic positive effect on attention as demonstrated in human electroencephalography studies, and in a behavioral study. Though there are only a few human data on the interaction of these two compounds, it is obvious that the ratio of theanine and caffeine determines the degree of stimulant effect of tea drinks. This effect has been confirmed in clinical studies as well.
L-theanine facilitates the generation of alpha waves in the brain, which are believed to be associated with a relaxed yet alert mental state. In rats, theanine administered after caffeine dosing blunted the stimulant effect of caffeine. However, there is an experimental evidence that L-theanine counteracts the stimulatory effect of caffeine. The purine alkaloid caffeine, the most widely applied stimulating agent, acts through adenosine receptors, whereas the mechanism of action of the anxiolytic, relaxing effect of the amino acid L-theanine is not fully discovered yet.
Pharmacological research focuses mainly on the polyphenols of tea due to their antioxidant, anticancer properties, nevertheless, tea drinkers experience the immediate effect of two other compounds: Both caffeine and theanine exert their activities on the central nervous system. Although the importance of tea ( Camellia sinensis L.) as a medicinal plant is increasing, this plant is above all a raw material of the food industry.
0 kommentar(er)
