Biosensoric detection of the cysteine sulphoxide alliin

Garlic (Allium sativum L.) and related species of the Alliaceae family are known for their cancer-protecting and anti atherosclerotic potential. The bioactivity of these plants is related to organo-sulphur compounds, mainly alliin. In the present investigation, an alliin-specific biosensor exploiting immobilised alliinase (EC 4.4.1.4) has been developed. Enzymatically formed ammonia was detected by a potentiometric sensor based on an ammonia electrode or a pH-sensitive electrolyte/insulator/semiconductor (EIS) layer structure made of Al/p-Si/SiO2/Si3N4. It could be demonstrated with both methods that this biosensoric approach yielded results comparable to sensitivities obtained by HPLC. Alliin concentrations down to 6 x 10(-6) M could be quantified. The EIS biosensor showed also sensitivity to further cysteine sulphoxides, like methiin, ethiin and propiin, which are common for wild Allium species. Besides the analysis of garlic and garlic-containing preparations, like herbal remedies, this biosensor can be additionally used for breeding research and screening purposes of potential medicinal plants. (C) 2003 Published by Elsevier Science B.V.