Development of techniques for the analysis of isoflavones in soy foods and nutraceuticals

Soy Isoflavones and their Effects on Xenobiotic Metabolism

BACKGROUND

Soy isoflavones, such as genistein and daidzein, are bioflavonoids found in soy products that are able to interact with various hormones such as estrogen. Epidemiological studies reveal a proper level of isoflavones in diet can prevent many diseases like cancers or diabetes. Therefore, it is important to study the biotransformation and xenobiotic metabolism of soy isoflavones.

METHODS

A systematic review of published studies was carried out to investigate the characterization of isoflavones and their metabolites, sample pretreatment and quantitative analysis of isoflavones, and the influence of soy isoflavones on drug and xenobiotic metabolism.

RESULTS

Aglycones with weak estrogen-like activities are the biologically active forms of the soy isoflavones in mammals. The most recent advances including extraction, purification and detection of isoflavones in soybean and soy products are discussed. The effects of soy isoflavones on drug and xenobiotic metabolism involve in regulation of phase I cytochrome P450 (CYPs) enzyme and phase I detoxifying enzymes expression and activity. At the molecular level, soy isoflavones have proved capable of estrogenic/antiestrogenic with tissue-selective, anti-cancer, antiobesity, anti-oxidation, and tyrosine kinase inhibition activities.

CONCLUSION

This review summarized different aspects of soy isoflavones and their molecular mechanisms of pharmacological action on xenobiotic, which demonstrated that soy isoflavones can decrease the incidence of many diseases and benefit for human health. However, since the lack of clinical research for evaluation of the proper dosage of intake of soy isoflavones in diet or adjunctive therapy, there is a need for further studies on the selection of doses, biomedical applications and adverse effects of isoflavones for human health.

Improving the estimation of flavonoid intake for study of health outcomes

Imprecision in estimating intakes of non-nutrient bioactive compounds such as flavonoids is a challenge in epidemiologic studies of health outcomes. The sources of this imprecision, using flavonoids as an example, include the variability of bioactive compounds in foods due to differences in growing conditions and processing, the challenges in laboratory quantification of flavonoids in foods, the incompleteness of flavonoid food composition tables, and the lack of adequate dietary assessment instruments. Steps to improve databases of bioactive compounds and to increase the accuracy and precision of the estimation of bioactive compound intakes in studies of health benefits and outcomes are suggested.

Fast and reliable class-selective isoflavone index determination on carbon nanotube press-transferred electrodes using microfluidic chips

Direct microfluidic electrochemical sensing of class-isoflavones in complex soy samples on press-transferred carbon nanotubes.

Comparison of different types of stationary phases for the analysis of soy isoflavones by HPLC

Nowadays, there are new technologies in high-performance liquid chromatography columns available enabling faster and more efficient separations. In this work, we compared three different types of columns for the analysis of main soy isoflavones. The evaluated columns were a conventional reverse phase particle column, a fused-core particle column, and a monolithic column. The comparison was in terms of chromatographic parameters such as resolution, asymmetry, number of theoretical plates, variability of retention time, and peak width. The lower column pressure was provided by the monolithic column, although lower chromatographic performance was achieved. Conventional and fused-core particle columns presented similar pressure. Results also indicate that direct transfer between particle and monolithic columns is not possible requiring adjustment of conditions and a different method optimization strategy. The best chromatographic performance and separation speed were observed for the fused-core particle column. Also, the effect of sample solvent on the separation and peak shape was evaluated and indicated that monolithic column is the most affected especially when using higher concentrations of acetonitrile or ethanol. Sample solvent that showed the lowest effect on the chromatographic performance of the columns was methanol. Overall evaluation of methanol and acetonitrile as mobile phase for the separation of isoflavones indicated higher chromatographic performance of acetonitrile, although methanol may be an attractive alternative. Using acetonitrile as mobile phase resulted in faster, higher resolution, narrower, and more symmetric peaks than methanol with all columns. It also generated the lower column pressure and flatter pressure profile due to mobile phase changes, and therefore, it presents a higher potential to be explored for the development of faster separation methods.

Fast analysis of isoflavones by high-performance liquid chromatography using a column packed with fused-core particles

The recent development of fused-core technology in HPLC columns is enabling faster and highly efficient separations. This technology was evaluated for the development of an fast analysis method for the most relevant soy isoflavones. A step-by-step strategy was used to optimize temperature (25-50°C), flow rate (1.2-2.7 mL/min), mobile phase composition and equilibration time (1-5 min). Optimized conditions provided a method for the separation of all isoflavones in less than 5.8 min and total analysis time (sample-to-sample) of 11.5 min. Evaluation of chromatographic performance revealed excellent reproducibility, resolution, selectivity, peak symmetry and low limits of detection and quantification levels. The use of a fused-core column allows highly efficient, sensitive, accurate and reproducible determination of isoflavones with an outstanding sample throughout and resolution. The developed method was validated with different soy samples with a total isoflavone concentration ranging from 1941.53 to 2460.84 μg g(-1) with the predominant isoflavones being isoflavone glucosides and malonyl derivatives.

The quality of commercially available nutraceutical supplements and food sources

OBJECTIVES

Nutraceuticals are components of dietary origin, with claimed beneficial therapeutic activities. The quality of nutraceuticals is paramount for efficacy and safety, and it includes quality of raw materials, different available chemical forms, complex products, lack of substitution of inappropriate materials, and the absence of contaminants. The aim of this review is to investigate the extent of substandard formulated and raw material nutraceuticals, and to highlight any consequent health concern.

KEY FINDINGS

Reports of the quality of raw materials have revealed wide variations, often as a result of lack of clear regulatory definitions with respect to size of polymeric entities and also presence of glycosidic and salt forms. Published evaluations of over 70 formulations of 25 different nutraceuticals revealed variable quality; no nutraceutical showed consistent high quality, but a number revealed consistent low quality, thereby making the case for closer regulation of manufacturers. Whole food sources have also been shown to be widely variable in constituent levels. The effect of different formulations requires consideration, as the different types have been shown to have marked effects on bioavailability.

SUMMARY

The poor quality of commercially available nutraceuticals has been highlighted. In addition, incidences of side effects and drug interactions are increasing, as consumption of nutraceuticals rises. Pharmacists and health practitioners need to be aware of the scientific literature to advise accordingly.

Non-isoflavone phytochemicals in soy and their health effects

Epidemiological and clinical studies have linked consumption of soy foods with low incidences of a number of chronic diseases, such as cardiovascular diseases, cancer, and osteoporosis. Over the past decades, enormous research efforts have been made to identify bioactive components in soy. Isoflavones and soy protein have been suggested as the major bioactive components in soy and have received considerable attention. However, there are hundreds of phytochemical components in soybeans and soy-based foods. In recent years, accumulating evidence has suggested that the isoflavones or soy proteins stripped of phytochemicals only reflect certain aspects of health effects associated with soy consumption. Other phytochemicals, either alone or in combination with isoflavones or soy protein, may be involved in the health effects of soy. This review attempts to summarize major non-isoflavone phytochemicals in soy, as well as their bioavailability and health effects. In addition, a brief discussion of components formed during food processing is also included.

Sample preparation for the analysis of isoflavones from soybeans and soy foods

This manuscript provides a review of the actual state and the most recent advances as well as current trends and future prospects in sample preparation and analysis for the quantification of isoflavones from soybeans and soy foods. Individual steps of the procedures used in sample preparation, including sample conservation, extraction techniques and methods, and post-extraction treatment procedures are discussed. The most commonly used methods for extraction of isoflavones with both conventional and "modern" techniques are examined in detail. These modern techniques include ultrasound-assisted extraction, pressurized liquid extraction, supercritical fluid extraction and microwave-assisted extraction. Other aspects such as stability during extraction and analysis by high performance liquid chromatography are also covered.