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Biotransformation of Xenobiotics in Living Systems—Metabolism of Drugs: Partnership of Liver and Gut Microflora
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
ß-Glucuronidase of bacterial origin is among the most examined bacterial enzymes due to its role in the deconjugation of glucuronidated metabolites from liver (for example morphine-6-glucuronide). This may result in subsequent enterohepatic circulation of drugs that may delay drugs excretion and prolong the action of drugs or even contribute to toxicity. Various bacterial genera express this enzyme, including Lactobacillus, Bifidobacterium, Clostridium, Streptococcus, Ruminococcus (Walsh et al., 2018; Wang and Roy, 2017). Similarly, ß-glucosidase hydrolyze the glycosidic bond thus releases the parent compound making a significant contribution to conversion of dietary plant substances into bioactive molecules (Michlmayr and Kneifel, 2014). Dietary plant substances that are the most susceptible to microbial degradation in the human intestinal tract are the phytochemicals (phenolics and flavonoids) (Swanson, 2015). Considering the popular use of traditional medicines and herbal supplements, more attention should be paid to microbially derived plant metabolites and their safety profiles.
Evaluation of Water and Its Contaminants
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 5, 2017
William J. Rea, Kalpana D. Patel
When humans defecate, urinate, sweat, or bathe, their organ systems are simultaneously getting rid of toxic substances. Ingested material first goes into the intestinal tract which attempts, through extensive enzyme systems, to break down the large molecule foodstuffs into smaller, more efficiently absorbed molecules of essential nutrients such as amino acids, simple sugars, and fatty acids, along with essential minerals and vitamins. These digested molecules mainly pass directly into the bloodstream (the “enterohepatic circulation”) that flows directly into the liver, which, among other functions, attempts to metabolize, detoxify, and excrete poisonous substances into the biliary system (back into the intestines, however), although many of the metabolized substances go into the bloodstream and thus to the rest of the body. Many of the partially detoxified drugs are still pharmacologically active and may still be toxic.
Systemic toxicology
Published in Chris Winder, Neill Stacey, Occupational Toxicology, 2004
W.M. Haschek, N.H. Stacey, C. Winder
Chemicals that enter the digestive tract may pass straight through and be excreted unchanged in the faeces; may be directly toxic to the mucosa; be absorbed, primarily by passive diffusion, into the epithelial cells; or may be metabolised by bacteria in the lumen. Once within the cell, a chemical may be directly toxic to the cell, metabolised to reactive or less toxic intermediates, or bound to protein before passing into the lymphatics or capillary bed. After passing through the liver, the absorbed chemical can then be excreted in the urine or the bile. Enterohepatic circulation occurs when the chemical excreted in the bile is absorbed from the intestines, re-enters the circulation, and is once more excreted by the liver into the bile. This process may be repeated several times resulting in concentration of the chemical and increased toxicity.
Process optimization in ginseng fermentation by Monascus ruber and study on bile acid-binding ability of fermentation products in vitro
Published in Preparative Biochemistry & Biotechnology, 2021
Chongyan Zhao, Fang Yang, Feng Lin, Qingsong Qu, Zhixun Li, Xing Liu, Lu Han, Xinyuan Shi
Cholesterol is a precursor to the synthesis of bile acids. About 80% of the cholesterol is metabolized by liver tissue and converted to bile acid, which is involved in the enterohepatic circulation. Finally, part of bile acid is reabsorbed by the body.[36,37] de Aguiar Vallim[38] reported that bile acids can bind some food ingredients and then excrete with the digestion of food. Therefore, Cholesterol will be continuously converted to bile acids to maintain the homeostasis of the bile acid pool, thereby reducing the cholesterol content in the blood. In the human body, bile acids are classified into free bile acids (cholic acid, deoxycholic acid, etc.) and conjugated bile acid (cholic acid, deoxycholic acid, etc. combined with glycine and taurine).[39] The conjugated bile acids are generally present in the form of sodium salts, which is more common in the human body. Therefore, in this study, it is applicable that sodium taurocholate and sodium cholate were selected as representative of the conjugated bile acids.
A critical review on the bioaccumulation, transportation, and elimination of per- and polyfluoroalkyl substances in human beings
Published in Critical Reviews in Environmental Science and Technology, 2023
Yao Lu, Ruining Guan, Nali Zhu, Jinghua Hao, Hanyong Peng, Anen He, Chunyan Zhao, Yawei Wang, Guibin Jiang
Enterohepatic circulation can lead to reabsorption of certain chemicals from bile back into blood and liver, which can influence the elimination process of chemicals (Cao et al., 2022). Previous observations indicated that the PFAS may have similar behaviors as bile acids, which possess a high reabsorption ratio through enterohepatic circulation (Ahrens & Ebinghaus, 2010; Consoer et al., 2016; Krøvel et al., 2008; Lupton et al., 2014; Shi et al., 2015). Therefore, the enterohepatic circulation may play an important role in the PFAS elimination process.