Aqueous acid extracts of wheat grains and potato exhibit after HPLC separation a series of compounds that are able to inhibit the bindln 8 of benzodiazepines to benzodlazepine receptors of rat brain membranes. In wheat one of the inhibiting compounds was shown to be identical to diazepam by means of HPLC characterization and gas chromatography combined with mass spectrometry. In potato one of the most prominent components in terms of binding inhibiting activity was identified as lormetazepam. In wheat and potato germination increases total inhibiting activity of the whole plant extracts as well as the content of the benzodiazepines approximately by factor five. Because uptake of benzodiazepines from the surrounding was excluded these flndinss indicate the biosynthesis of the benzodiazepines diazepam and lormetazepam by the plants investigated.