Uses and Applications of Amines.A big quantity of simple and complex amines occurs in the nature, and others with biological activity have been synthesized in the lab.

Many low molecular weight amines have very foul odours. Trimethylamine [(CH3)3N] , formed when enzymes break down certain fish proteins, has the

characteristic odour of rotting fish.Putrecine and cadaverine are both poisonous diamines with putrid odours. They, too, are present in rotting fish, and are partly responsible for the odours of semen, urine, and bad breath. Naturally occurring amines derived from plant sources are called alkaloids, these include quinine, morphine cocaine, atropine, nicotine and coniine.

Histamine and Antihistamines.

Histamine, a rather simple triamine, is responsible for a wide variety of physiological effects. Histamine is a vasodilator (it dilates capillaries), so it is released at the site of an injury or infection to increase blood flow. It is also responsible for the symptoms of allergies, including a runny nose and watery eyes. In the stomach, histamine stimulates the secretion of acid. Understanding the central role of histamine in these biochemical processes has helped chemists design drugs to counteract some of its undesirable effects.

Antihistamines bind to the same active site of the enzyme that binds histamine in the cell, but they evoke a different response. Brompheniramine, for example, inhibits vasodilation, so it is used to treat the symptoms of the common cold and allergies. Cimetidine is a histamine mimic that blocks the secretion of hydrochloric acid in the stomach, so it is used to treat ulcers.

Trimethylamine is the compound responsible for the characteristic odour of rotting fish

Cimetidine commercially named Tagamet, an antiulcer drug

Derivatives of 2-Phenylethylamine.

A large number of physiologically active compounds are derived from 2-Phenylethylamine (C6H5CH2CH2NH2). Some of these compounds are synthesized in cells and needed to maintain healthy mental function. Others are isolated from plant sources or are synthesized in the laboratory and have a profound effect on the brain because they interfere with normal neurochemistry. These compounds include adrenaline, noradrenaline, methamphetamine, and mescaline.

Another example, dopamine, is a neurotransmitter, a chemical messenger released by one nerve cell (neuron), which then binds to a receptor in neighbouring target cell. Dopamine affects brain

processes that control movement and emotions; so proper dopamine levels are necessary to maintain mental and physical health.

Understanding the neurochemistry of these compounds has led to the synthesis and availability of several useful drugs, Fentanyl is a common narcotic pain reliever used in surgical procedures, and sumatriptan is used to relieve pain and light sensitivity in patients who suffer from migraine headaches.

Cocaine, amphetamines, and several other addicting drugs increase the level of dopamine in the brain, which results in a pleasurable “high”. With time, the brain adapts to increased dopamine levels, so more drug is required for the same sensation.

Synthetic Dyes.

Until 1856 all dyes were natural in origin, obtained from plants, animals, or minerals. Three natural dyes known for centuries are indigo, tyrian purple, and alizarin. But everything changed when William Henry Perkin serendipitously prepared a purple dye, which would later be called mauveine. Mauveine is a mixture of two compounds that differ only in the presence of one methyl group on one of the aromatic rings. This event began the surge of research in organic chemistry in the production of synthetic dyes, perfumes, anaesthetics, inks, and drugs as well.

Although natural and synthetic dyes are quite varied in structure, all of them are coloured because they are highly

Peyote, a cactus native to Mexico and south-western US, contains mescaline, a hallucinogen.

Cocaine, an addicting drug which increases the level of dopamine

Indigo Plant

conjugated. A molecule with eight or more bonds in conjugation absorbs light in πthe visible region of the electromagnetic spectrum, taking the colour from the visible spectrum that it does not absorb.

To be classified as a dye, a compound must be coloured and it must bind to fabric. There are many ways for this binding to occur. Compounds that bind to fabric by some type of attractive forces are called direct dyes. These forces may involve electrostatic interactions, van der Waals forces, hydrogen bonding, or sometimes, even covalent bonding. The type of interaction depends on the structure of the dye and the fibre. Thus, a compound that is good for dyeing wool or silk, both polyamides, may be poor for dyeing cotton, a carbohydrate.

Sulpha drugs

Although they may seem quite unrelated, the synthesis of coloured dyes led to the development of the first synthetic antibiotics. The German chemist Paul Ehrlich, who worked with synthetic dyes and used them to stain tissues, did much of the early effort in this field. This led him on a search for dyes that were lethal to bacteria without affecting other tissue cells, hoping that these dyes could treat bacterial infections. For many years tis efforts was unsuccessful.Then in 1935, Gerhard Domagk first used a synthetic dye as a drug to kill bacteria. His daughter had contracted a streptococcal infection, and as she neared death, he gave her prontosil, an azo dye that inhibited the growth of certain bacteria in mice. His daughter recovered, and the modern era of synthetic antibiotics was initiated.

Prontosil and other sulpha-containing antibiotics are collectively called sulpha drugs. Prontosil is not the active agent itself. In cells, it is metabolized to sulphanilamide, the active drug.

Prontosil, a commercial sulpha-containing antibiotic