Colonic Bacterial Enzymes: Pharmaceutical Significance and Applications

Colonic Bacterial Enzymes: Pharmaceutical Significance and Applications

Srushti M. Tambe (Bombay College of Pharmacy, India) and Namita D. Desai (Bombay College of Pharmacy, India)
DOI: 10.4018/978-1-5225-5237-6.ch004
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This chapter reviews various enzymes produced by the colonic microflora and their utilization in the development of pharmaceutical dosage forms to achieve colon-specific drug delivery. This chapter discusses the applications of colonic bacterial enzymes in order to surrogate colonic conditions in vivo so as to evaluate in vitro drug release from microbially triggered/enzymatically triggered colon-specific drug delivery systems. This chapter also discusses different methods to produce colonic bacterial enzymes as well as use of probiotics as a source to produce colonic bacterial enzymes.
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The human colon comprises of a wide range of microflora representing approximately 1011-1012 CFUs/ml with more than 400 bacterial species such as Bifidobacteria, Bacteroides, Clostridia etc. These bacterial species residing in the colon are capable of producing more than 500 different types of enzymes. The fermentation of various substrates that are left undigested in the small intestine after reaching the colon acts as a source of energy for the colonic bacteria in order to maintain their cellular functions. These substrates include disaccharides and trisaccharides such as lactulose, cellobiose, raffinose, stachyoseas well as partially fermented residues of polysaccharides such as pectins, galactomannans, xylans, etc. The colonic microflora produces wide range of bacterial enzymes such as α-D-galactosidase, β-D-glucosidase, β-xylosidase, β-arabinosidase, β-D-glucuronidase etc., to carry out fermentation of substrates (polysaccharides or dietary fibers). These bacterial enzymes are also capable of degrading the various polysaccharide-based coatings/matrices as well as break the bonds between the inert carrier and an active drug moiety resulting in the release of active drug in the colon without being affected in the upper gastrointestinal tract (GIT). Taking this into consideration, several formulations have been developed to achieve colon targeting by using polysaccharides and carriers that are readily degraded by the colonic microflora but unaffected by the microflora present in the upper part of GIT. These systems, after reaching the colon are fermented (polysaccharide-based systems) or broken down (prodrug-based systems) by the colonic bacterial enzymes, thereby causing complete drug release in the colon. These approaches have been utilized in the treatment of various colonic conditions such as Crohn’s disease, ulcerative colitis, diarrhea, constipation, amoebiasis and colorectal cancer. Additionally, these systems are utilized to avoid first pass metabolism of the drugs that are degraded in the upper gastric environment. Colonic bacterial enzymes have also found its applications in the in vitro release evaluation of colonic formulations serving as a discriminatory and biorelevant method to evaluate drug release from enzymatically/microbially triggered colonic formulations. Colonic bacterial enzymes that are specific to the substrate e.g. pectinases for pectin-based colonic formulations or a mixture of several colonic bacterial enzymes representing the entire colonic microflora are employed during the dissolution studies under anaerobic conditions in order to simulate colonic conditions and assess drug release from the colonic formulations. This chapter reviews the importance of colonic bacterial enzymes, their production methods as well as their utilization to develop various formulations for achieving colon-specific drug delivery.

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