摘要:

AbstractSoybean consumption is associated with reduced rates of prostate and other cancers, possibly due in part to the presence of isoflavones. The metabolism and disposition of these soya‐derived phytoestrogens after chronic soya exposure were studied on a metabolic unit in six healthy males (21–35 yrs of age) who consumed an unrestricted hospital diet and a 12‐oz portion of soymilk with each meal for one month. The daily isoflavone intake was about 100 mg of daidzein (mostly as daidzin) and about 100 of mg of genistein (mostly as genistin). At two‐week intervals, excretion of isoflavones in urine was studied, during which time the subjects consumed a constant basal diet for three to four days, ingested the full daily 36‐oz portion of soymilk within 30 minutes each day for one to two days, and collected urine continuously. The urinary recovery of ingested daidzin plusdaidzein (46.9±15.2%, mean±SD) and genistin plus genistein (14.6±9.2%) didnotchange with prolonged soya ingestion. The absorption half‐lives (t1/2) for daidzein and genistein and the appearance t1/2for equol (1 subject) were initially 1.5±0.4, 1.9±0.6, and 2.2 hours, respectively, and 2.5 + 1.1 (p = 0.06 compared with baseline), 1.4±0.9 (p = 0.03 compared with baseline), and 4.2 hours, respectively, during one month of soymilk ingestion. The excretion t1/2for daidzein, genistein, and equol were initially 2.9 + 0.5, 3.8±0.7, and 5.2 hours, respectively, and 3.9 + 1.2 (p = 0.03), 5.5±1.6 (p = 0.02), and 9.7 hours, respectively, during one month of soymilk ingestion. These results indicate that chronic soya exposure did not induce significant changes in the metabolic pathways of isoflavones but altered the time courses of daidzein and genistein excretion. Thus chronic exposure to soya might prolong the tissue exposure to the presumed biologically active free and unconjugated forms of these isoflavones and thereby enhance their oncoprotective effects.

ISSN:0163-5581    

DOI:10.1080/01635589509514420

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor

摘要:

AbstractNeoxanthin, a major carotenoid pigment of spinach, is found in the chloroplast membrane and has an unknown function in plants. Neoxanthin inhibited the production of superoxide onions in an artificial xanthine and xanthine oxidase system and depressed DNA synthesis in methylcholanthrene (MCA)‐initiated C3H10T1/2 fibroblasts. In two‐stage carcinogenesis experiments, neoxanthin at 0.2μg/0.2 ml inhibited the formation of tumors that were induced sequentially by 7,12‐dimethylbenz[a]anthracene (DMBA) and 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in the buccal pouch of Syrian Golden hamsters. To assess the ongoing process of carcinogenesis, the activity of ornithine decarboxylase (ODC), required for cell proliferation, was analyzed. Neoxanthin inhibited the activity of ODC when animals were treated with neoxanthin one hour before the application of TPA in two‐stage carcinogenesis. However, neoxanthin did not inhibit ODC activity when animals were treated with neoxanthin one hour before the application of DMBA in two‐stage carcinogenesis, and there was no subsequent tumor formation. In a short‐term anti‐initiation experiment, neoxanthin inhibited the covalent binding of isotope‐labeled DMBA to DNA by 53%. These results indicate that neoxanthin inhibits the initiation stage and the promotion stage in two‐stage carcinogenesis. This suggests that neoxanthin may act as a potential chemo‐preventive agent.

ISSN:0163-5581    

DOI:10.1080/01635589509514421

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor

ISSN:0163-5581    

DOI:10.1080/01635589509514409

出版商:Taylor&Francis Group    

年代:1995

数据来源: Taylor