Certified Reference Materials Preparation And Determination Of Soybean Isoflavones

Soy isoflavones, as a subgroup of the flavonoid family, occur naturally in legumes and are cosumed regularly in the human diet. In the past few years, a great diversity of the biological activities and the pharmacological functions on soybean isoflavones, such as antioxidation, anticancer, antitumor, estrogenoid and antiestrogen, prevention of cardiovascular diseases and relief of menopausal syndrome, have been proved and also endows its abundant utilization values. All of these reveal that soybean isoflavones have a brilliant prospect in the fields of functional foods and medicines. In the future, there will be lots of soy and soy foods, as rich sources of isoflavones, coming into the market. So it is necessary to setup the standard analysis method and offer Certified Reference Materials (CRMs) for the quality control and the quality assurance of related products. In this thesis, the preparation and the value determination of the CRMs of soybean isoflavones were investigated.In this thesis, daidzein, genistein, daidzin, glycitin and genistin, five soybean isoflavones were preparated. In the preparation, first, they were extracted by ethyl acetate from the extracts of soybean and the acid hydrolysis products of soybean crude extracts. Then they were preparatorily isolated according to their different solubilities in different solvents. The silica gel chromatography, Pharmadex LH-20 gel chromatography and RP-HPLC were applied to further separate and purify these soybean isoflavones.An independent method, high performance liquid chromatography (HPLC), for the isoflavone CRMs value determination was developed with high accuracy and precision. The results showed that the contents of isoflavones in CRMs are more than 99 %. Their structures were characterized by ultraviolet spctrometry(UV), infrared spectrometry(IR), mass spectrometry (MS)and nuclear magnetic resonance (NMR).