They usually have a bitter taste and are characterised by powerful physiological activity. Examples are nicotine and caffeine. Antioxidant A compound which retards oxidation. Caffeine An alkaloid found in tea and coffee which acts as a nerve stimulant and diuretic. Catechins A group of related polyphenolic compounds which occur in plants and are darkened by the action of certain plant enzymes and oxygen an example of browning of cut fruit and vegetables.
Catechins can function as antioxidants.
Cardiovascular concerning the heart and blood vessels. Carcinogen Any substance or agent that can produce a cancer. Diuretic An agent that promotes increased excretion of urine. A family of substances related to the simple catechins which occur in green tea and which undergo browning reactions during processing to black tea. Free radical A highly reactive substance which, in some circumstances can lead to undesirable chemical changes in the body through oxidisation, e.g. hardening of the blood vessels and development of cancer.