Catechin (English: Catechin), also known as tea tannin and catechol, is the general name of flavanols (flavanols -3- alcohols) in tea. Catechin is the most important kind of tea polyphenols, accounting for about 75% to 80% of tea polyphenols, and it is also one of the sources of bitter taste of tea.

Catechins are mainly divided into four types:

Epicatechin EC (epicatechin EC)

Epigallocatechin EGC (EGC)

Epicatechin gallate ECG

Epigallocatechin gallate EGCG.

Catechin is flavan -3- alcohol, a natural phenol and antioxidant. It is a secondary metabolite of plants. It belongs to the group flavan -3- alcohol (flavanol), a part of the chemical family of flavonoids. The name of the chemical family of catechins is obtained from catechu, which is the juice or boiled extract of Mimosa or Acacia catechu.

Catecholamines, a common hormone in human body, is a general term for (phenylethyl) amine compounds with catechol nucleus, and it is a kind of stress-sympathetic "Fight or Flight" hormone produced by adrenal gland. The most important catecholamines are adrenaline, Epinephrine and Dopamine, all of which are synthesized from phenylalanine and tyrosine. Many psychostimulants are also analogues of catecholamine.