Izoflawony – struktura, aktywność biologiczna oraz metody oznaczania przy użyciu wysokosprawnej chromatografii cieczowej

Isoflavones are a subclass of flavonoids and are also described as phytoestrogen compounds, since they exhibit estrogenic activity (similar effects to estradiol hormones). The basic characteristics of isoflavone structure is a flavone nucleus, composed of two benzene rings (A and B) linked to a heterocyclic ring C (Fig. 1). The benzene ring B position is the basis for the categorization of a flavanoid class (position 2) and a isoflavonoid class (position 3) [8]. Isoflavones are classified according to substitutions. The glucoside forms can be esterified at the 6’’-O-position of the glucose ring with malonyl or acetyl groups forming another compounds. In food and plants, flavonoids exist primarily as 3-O-glycosides and polymers [14]. Isoflavonoids are a group of chemical compounds which is widely distributed in the vegetable world. Their biological activity has found remarkable pharmaceutical, therapeutic, dietary and nutritional applications. The structure of phytoestrogens enables them to bind to the estrogen receptors (ERs), they are similar to 17β-estradiol, contain an aromatic ring with hydroxyl group and have the binding affinity to both estrogen. In addition, isoflavones interact with the metabolism of steroid hormones. Recently, they have come into focus of interest due to several reports about their positive effect on human health, in particular prevention of hormone-dependent cancers, cardiovascular diseases, osteoporosis, adverse menopausal manifestations and age-related cognitive decline. To identify the potential health benefits associated with the consumption of isoflavones, it is of critical importance to have high-quality and comprehensive data. To this end, adequate analytical methodologies are essential for a reliable and exact identification as well as for quantification. Moreover, methodologies and techniques used need to keep up with technology to improve the performance in terms of resolution, efficiency, precision, reproducibility and speed, allowing a proportionate increase in the amount and quality of information gathered [7]. Common methods for the extraction of isoflavones from soybeans and soy products include organic solvent extraction with aqueous methanol, ethanol or acetonitrile, using simple mixing, ultra-sonification or refluxing techniques [24]. The application of micro-scale and nano-scale extraction and separation techniques is the most likely future development, resulting in quick, sensitive analytical methods for sample preparation and analysis of flavonoids and their metabolites. Miniaturization, high-throughput systems utilizing new sorbents and automation of chromatographic systems are of great interest in clinical, pharmaceutical, environmental and food fields. The most used analysis technique for the quantification of isoflavones in solid samples is, with no doubt, reversed-phase HPLC using C18 based columns with water and methanol or acetonitrile containing small amounts of acid as a mobile phase [7].