They usually have a bitter taste and are characterised by powerful physiological activity. Examples are nicotine and caffeine. Antioxidant - A compound which prevents 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. Free radical - A highly reactive chemical 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. Flavanols, flavonols, flavonol glycosides, flavandiols - Groups of related, naturally occurring chemicals in plants.