| Genistein, a principal soy isoflavone and a kind of plant estrogen with bioactivity, exists in leguminosae plant in the form of genistin, especially in soy and its products. Genistein, an antioxidant in vitro and in vivo, can inhibit tyrosinekinase and have estrogenic activity. Genistein plays a potential role in preventing estrogen-related cancers, osteoporosis and cardiovascular disease. This study aims at revealing the dynamic rules of genistein in rats, clarifying the process and properties of ADME and calculating pharmacokinetic parameters.1.Determine the physical and chemical constans of genistein The solubility in different solvents, the oil/water detached coefficient and pKa value of genistein were determined by UV spectrophotometry. The results showed that the solubility of genistein in methyl alcohol, ethanol and acetone were higher than that in other solvents. The oil/water detached coefficient was higher in acid solvent. The pKa value of genistein was 7.9942.2. Study the pharmacokinetics of genistein2.1 Establisment of HPLC methods Genistein in plasma, urine and homogenized feces was extracted by methyl tert-butyl ether and pentane. Genistein was detected by high-performance liquid chromatography. This method showed a good speciality, recurrence and high sensitivity with fine linearity during 0.025-10ug-ml-1. The minimum detective concentration was12ng-mr'.2.2 Concentration-time curve The concentration of genistein was determined at different time after iv(9mg-kg" ) or ig at the dose of 3.125mg-kg-1, 6.25mg-kg-1, 12.4mg-kg-1 or 50mg-kg-1 respectively. The concentration of genistein glucuronide conjugates was determined by hydrolyzation of glucuronidase. The data were analysed by 3P97 and pharmacokinetic parameters were attained under different conditions. The results indicated that the concentration-time(C-T) curve of iv was fitted two-compartment model and the C-T curve of ig had a complex expression.2.3 Experiment of tissue distributionGenistein had high fat solubility and better membrane permeability. The distribution was fast and extensive. After administration of 10 minutes, the concentrations of main organs were as follows: liver > kidney > ovary > lung >heart> muscle> uterus> brain > fat > plasma > testicle. After administration of 80 minutes, the concentrations of main organs were as follows: liver > kidney > ovary> muscle> uterus > spleen > brain > testicle > plasma; After administration of 360 minutes, the concentrations of main organs were as follows:liver > kidney > lung > heart > fat > spleen > testicle > ovary > brain > uterus > plasma>muscle.2.4 Experiment of protein binding Protein binding test of genistein was conducted in vitro by using dialysis. There was high affinity between genistein and protein. The binding was concentration-dependent. When concentration was lower, the binding ratio was lower. The binding arrived at state of saturation, when concentration increased.This may be one reason of nonlinear dynamics.2.5 Experiment of excretionGenistein was given to the SD rats by gastrogavage at the dose of Pmg.kg"1. A portion of genistein was excreted to the outside of the body in the form of glucuronide conjugates by urine and feces. The ratio of genistein in urine was 3.5% of the total, the ratio of glucuronide conjugates was 6.6%, and the ratio of genistein and glucuronide conjugates was 21.09%, which suggested that portions of genistein could be eliminated by transforming other metabolites.3. Test on bioavailability of genistein capsuleConcentration of genistein in serum was determined by HPLC after ig(9mg-kg-1). The 3P97 program was used to calculate the pharmacokinetic parameters. Its bioavailability was 56.49% when genistein was served as estimate index. When genistein plus glucuronide conjugates were served as estimate index, F was 82.17%.
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