Cyanogenic Glycosides in Plant Foods

Consumption of cyanogenic plants can cause serious health problems for humans. The ability to detect and quantify cyanogenic glycosides, capable of generating cyanide, could contribute to prevention of cyanide poisoning from the consumption of improperly processed cyanogenic plants. In the first part of the present study, an efficient extraction method for amygdalin from foods was developed by comparing the extraction efficiency of water and ethanol at room and boiling temperature for various extraction times. Efficiencies of the extraction methods were evaluated by using a modified HPLC method. In general, boiling ethanol was more efficient for amygdalin extraction from foods. Amygdalin contents of a wide range of commercially-available food products were determined for the first time. In the second part, the effect of processing on amygdalin levels in apple juice was investigated. Apple juices produced from different apple varieties were subjected to various processing conditions such as freezing, pasteurization and holding for various times. The results obtained showed that processing can result in reduction of amygdalin level in apple juice and that the reduction of amygdalin by enzymatic degradation probably depends on the level of the enzyme in the processed foods and the utilisation of optimum conditions for the enzyme activities. High-temperature treated commercially-available apple juice had lower amygdalin levels compared to low-temperature treated juices, indicating the degradation of amygdalin at high processing temperatures. In the last part, the development of a sensitive ELISA method for amygdalin was investigated. Antibody produced by using an immunogen that was synthesized using the cyanuric chloride method for coupling of hapten to carrier protein was highly immunoreactive and very specific for amygdalin. The ELISA developed using this antibody was very sensitive (LOD = 0.2ng/ml). The results obtained from the determination of amygdalin in foods using the ELISA method showed excellent correlation with those obtained from HPLC method. The work described is the first comprehensive study on detection of a particular cyanogenic glycoside and use of an antibody-based method for determination of amygdalin in processed foods. The results obtained suggested that while the consumption of products available in the UK with the potential for containing amygdalin are unlikely to present a health risk to consumers, monitoring of new processing protocols would be wise.