# Soy Isoflavones and PCOS: Role in Hormonal and Metabolic Mechanisms
## 3 Biochemistry of Soy Isoflavones  
### Genistein  
Genistein, also known as 5,7-dihydroxy-3-(4-hydroxyphenyl)chrom-4-one, is one of the best-researched compounds in the isoflavroup group [28]. It was first isolated from _Genista tutoria_ L., a member of the Fabaceae family, from which its name is derived [29], Genistein occurs naturally in various plant-derived foods, including legumes, fruits (e.g., apples, grapes, strawberries), seeds (e.g., sunflower), and vegetables such as cauliflower, broccoli, onions, spinach, cabbage, and tomatoes, as well as in clover and alfalfa sprouts. However, the main dietary source remains soybeans and their products [30; 31; 32]. In foods, genistein is usually found in a glycosidic form--as genistin. For intestinal absorption to occur, it must first be hydrolys into its active aglycone form (genistein), a process facilitated by the enzyme lactase-phlorizin hydrolase or by gut microbiota [33], primarily from the genera _Dorea_, _Sutterella_, _Parabacteroides_, _Bifidobacterium_, and _Lactobacillus_[34]. The genistein and genistin content in soy products varies depending on the degree of processing. In non-fermented soy products--such as raw soybeans, soy milk, soy nuts,  
Figure 1: Methodology selection flowchart. or tofu--the glycosidic form predominates. Genistin levels in such products can range from approximately 200.6 to 968.1 ug/g, whereas biologically active genistein is present at significantly lower levels, typically between 4.6 and 18.2 ug/g. Similar proportions are observed in soy milk and tofu (1.9-13.9 ug/g genistein; 94.8-137.7 ug/g genistin). Fermentation significantly alters isoflavone content. Fermented soy products such as miso and natto contain markedly higher levels of free genistein--ranging from 38.5 to 229.1 ug/g [32], with raw tempeh containing up to approximately 280 \(\pm\) 110 ug/g [35]. This increase results from the enzymatic activity of fermentative microorganisms, which cleave \(\beta\)-glycosidic bonds in genistin molecules, removing the sugar moiety and converting it into free, active genistein. Although genistin remains present in fermented products, the proportion of aglycone increases substantially [32]. Although genistein is efficiently absorbed from the gastrointestinal tract, its oral bioavailability is limited to approximately 10% [36; 37; 38]. This is attributed, among other factors, to its lipophilic nature, which results in poor water solubility, extensive metabolic transformations [39; 40; 41; 42], and the activity of efflux transporters responsible for removing the compound from cells [37]. The vast majority of ingested genistein undergoes accumulation and biotransformation primarily in the intestine and liver. The main metabolic pathways involved in this process are glucuronidation and sulfation. These reactions lead to the formation of conjugated metabolites--glucuronides and sulphates--which dominate in the systemic circulation and exhibit limited biological activity [37]. The involvement of cytochrome P450 (CYP) enzymes in genistein metabolism is relatively minor [38; 43] and appears to be confined mainly to less prominent hydroxylation pathways [44]. Following prior hydrolysis of genistin (the glycosidic form of GEN) by microbial enzymes, free genistein can either be absorbed or further metabolised in the colon by gut bacteria. In this environment, secondary microbial metabolites such as dihydrogenenist (DH-GEN), 6\({}^{\prime}\)-hydroxy-O-desmethylangolensin (6\({}^{\prime}\)OH-ODMA), and 4-ethylphenol (4 EP) can be produced. These transformations occur exclusively through the activity of the intestinal microbiota. However, there is substantial variability between individuals in their ability to generate these metabolites, primarily due to differences in gut microbiota composition. Not all individuals harbour microbial species capable of catalysing specific steps in these metabolic pathways. This results in marked variations in the post-ingestion metabolite profile of isoflavenes between individuals and across species [44].