Gastrointestinal tract molecular stability

Table 2.1 presents examples of the main classes of low-molecular-weight bioactive molecules which are currently considered to be helpful for human well-being and which can be therefore used as food supplements as well as active components in skin-care applications (Ratnam et al., 2006 McClements et al., 2009). The required physicochemical properties of effective bioactive compounds, which should be considered in the formulation of the prophylactic and therapeutic dietary supplements at their desired oral dosages, are described in the scientific literature. These properties are (i) solubility in aqueous media (ii) permeability through the gastrointestinal tract and cell membranes (iii) physical stability and (iv) bioavailability. 

A large proportion of bacterial siderophore uptake studies were centered on enteric bacteria as typified by E. coli and S. typhimurium. These bacteria possess a cell wall consisting of an outer membrane layer and a peptidoglycan layer. The former acts as a molecular sieve-type barrier, and the latter confers mechanical stability. Thus, the metabolically active cytoplasmic membrane is protected against bile salts and hydrolytic enzymes found in the mammalian gastrointestinal tract. The outer membrane... 

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