Soy Dietary Supplements – Quantitation of Isoflavonoids, Quality Control, and Content Uniformity using NMR Spectroscopy

Herbal-based dietary supplements are a rapidly expanding market with increasing regulatory controls in many countries. NMR spectroscopy is a powerful tool for measuring, testing, and controlling the composition of these products. Soy-based supplements can contain both specific chemical ingredients such as genistin and a mixture of herbs or other biological ingredients. Using rapid and fully-automated NMR techniques, products like these can be tested for potency of labeled ingredients as well as the overall character of the product. In this study, three different over the counter formulations were investigated for potency, the presence of process-induced degradation, and content uniformity using a single, 3 minute per sample analysis. Verification and quantitation of the labeled isoflavonoid ingredients was straightforward, showing reasonable agreement with the expected results. The presence of genistein, a degradant created during the extraction of genistin from soybeans, was quantitated in each sample. The ratio of genistein to genistin indicates the harshness of the extraction process used to manufacture the raw soy material. Finally, PCA analysis was used to investigate the variability of the products with respect to each other and within tablets of the same product.