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The prevention of osteoporosis by nutritional phytoestrogens

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Speedy immunoassay for isoflavones

Research into the effects of therapies at a biomolecular level requires efficient bioassay techniques to test the efficacy of these methods. Scientists in the project consortium PHYTOS have developed a rapid assay procedure for quantitative analysis with a high degree of sensitivity.


The menopause and its effects, including the possible loss of bone density, is a source of anxiety for many women. As a remedy, hormone replacement therapy is an option but some women choose to go the more natural way and include naturally occurring phytoestrogens in their diet. These are present in high quantities in soy products but are contained in many other foods, like bananas. To date however, their efficacy has been anecdotal. PHYTOS, a European funded project, aimed to prove that isoflavones, a type of phytoestrogen, could prevent osteoporosis in postmenopausal women. An extensive multi-centre controlled trial was conducted in three European countries. As part of this research, workers at the University of Helsinki focused on the biochemical aspects of developing a sensitive reliable assay for isoflavan equol. Equol may have important physiological effects on the adverse effects caused by menopause. In trials of this nature, there is a vast amount of data spread over centres in a large geographical area. It is therefore important that assay procedures involved can be performed quickly and accurately with routine laboratory equipment. Prior to this research, the procedure used to ensure the sensitivity required was Gas Chromatography/Mass Spectrometry (GC-MS) but this is expensive and cumbersome. The Helsinki research team worked on the development of a time-resolved fluoroimmunoassay (TR FIA). Immunoassays have the advantage of being a high throughput method that uses routine laboratory equipment. The method involved coupling the isoflavin to bovine serum albumin and then using this as an antigen to immunise rabbits. The radioactive tracer europium chelate was used and then the immunoassay was carried out using plasma or urine. The plasma method gave highly specific results. Overestimation occurred when urine was tested but a formula could be use for correction purposes. The commercial exploitation of these results could have great potential. Within the scope of this study, it allows the simplification of studies of the effects of phytoestrogen compounds in humans. These methods are also applicable in a wide range of studies where biochemical assay methods are required.

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