Heterocycles as physiological ligands for the benzodiazepine receptor and for other binding sites

Recently pharmacologically active benzodiazepines, including diazepam, have been identified in common foodstuffs, e.g. wheat and potato. The chronical intake by way of plant food may explain the existence of benzodiazepines in the brain and in other tissues of various mammalians and man. Hitherto these alkaloid-like compounds were considered to be merely products of industrial synthesis. All the benzodiazepines used in therapy show a similar chemical structure. However, depending on particular substituents, agonistic benzodiazepines can be subdivided into groups of different pharmacological potency. Besides benzodiazepines, in the past years other alkaloid drugs, e.g. derivatives of morphine, norharmane and tetrahydronorharmane, have been isolated from animals. Some of these substances have been discussed as physiological ligands of specific neuronal binding sites. Indications have been provided that at least part of these compounds or their precursors may be of plant origin too. The presence of these compounds in plants used for food may suggest complex interactions between plant and animal, exceeding the nutritional aspect.