Genistein extraction

Isoflavones have been implicated in goiter induction. Soybean extracts inhibit reactions catalyzed by thyroid peroxidase (TPO), essential to the synthesis of thyroid hormones (Divi et al., 1997). Genistein and daidzein (at about 1-10 p,M of IC50) may act as alternative substrates for tyrosine iodination (Divi et al., 1997). Furthermore, genistein and daidzein have also been shown to cause the irreversible inactivation of TPO in the presence of hydrogen peroxide. Genistein also inhibits thyroxine synthesis in the presence of iodinated... 

The isoflavones found in soy bean extracts, such as genistein and daidzein, that are phytoestrogens, are also able to enhance HA deposition.281,282 Their estrogen-like structures may account for their ability to enhance HA deposition. 

Fig. 5-8. Examples of phenolic extractives and related constituents. 1, Gallic acid 2, ellagic acid 3, chrysin 4, taxifolin 5, catechin 6, genistein 7, plicatic acid 8, pinoresinol 9, conidendrin 10, pinosylvin 11, /3-thujaplicin.

In a study of retail soy foods, Murphy et al. (1999) optimized extraction of isoflavones and found that the amount of water included in the mixture of acetoni-trile-0.1 N HCl-water affected the yield of isoflavones in various foods matrices. Two grams of samples were extracted with 10 ml acetonitrile, 2 ml of 0.1 N HC1 and an amount of water. The optimal amount of water ranged from 5 to 10 ml, depending upon the type of food matrix. The standard deviation of the optimized extractions ranged from 0.6% to 4.8% for total daidzein and 0.2-3.5% for genistein analysis. HPLC with a C18 column was used to separate the isoflavones, which were... 

Chandra and Nair (1996) used supercritical carbon dioxide fluid extraction for extracting daidzein, genistein, biochanin A and formononetin from soy products. The separation was done by HPLC with a C18 column, followed by UV detection at 254 nm. Ninety-three percent of the isoflavones were extracted by using the supercritical fluid carbon dioxide with 20% ethanol at 50°C and 600 atmospheric pressure. 

Aussenac et al. (1998) used capillary zone electrophoresis with UV detection at 260 nm to analyze isoflavones in soybean seeds of various varieties grown in various locations. Methanol was used for extraction. Total extraction was not affected by temperature but was affected by the composition of the solvent. Electrophoresis was conducted at pH 10.5, at which the isoflavones were weak acids and were ionized. Boric acid was added to form a negatively charged borate-isoflavone complex. A fast capillary electrophoresis method was also developed by Vanttinen and Moravcova (1999) to determine daidzein and genistein after enzyme hydrolysis in soy products. Photodiode array was used to detect the isoflavones at 254 and 268 nm, respectively. Minimum detection was 0.4 mg/L. p-Nitrophenol was used as an internal standard. 

In 1964, Gyorgy and coworkers isolated daidzein and genistein along with 6,7,4 -trihydroxyisoflavone from tempeh and found that they possessed antioxidant activities. The activity of 6,7,4 -trihydroxyisoflavone was particularly effective. An extract of the soybean without fermentation had very little activity. However, acid hydrolysis with HC1 increased the soybean extract to that of tempeh. They assumed that... 

Shen (1994a,b) treated protein extract slurry with P-glucosidase, pH 6-8, to produce aglycones, then separated the soluble protein extract with the insoluble spent flakes, which was an aglycone-enriched soy fiber. The dried fiber fraction contained 1-2 mg genistein/g and 0.7-1.7 mg soy hber/g. 

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