Pectin-aluminum complex

Aluminum is an amphoteric element that acts as a nonmetal in alkali and develops a hydrated gelatinous aluminate of a species [Al(OH)4]. As a result of this reaction, certain suspended matter including polysaccharide polyanions coprecipitates by entrainment. This element, applied in atomic or ionic form, is a common technique for commercial isolation of pectin. In acid, Al3+ supposedly neutralizes polyanions to yield the aluminum salt. After precipitation of the pectin-aluminum complex, the metal ligand is removed by acidification and washing. 

KaoUn powder and other hydrated aluminum silicate clays, often combined with pectin (a complex carbohydrate), are the most widely used adsorbent powders (e.g., Kaopectate). Kaolin is a naturally occurring hydrated aluminum silicate that is prepared for medicinal use as a very finely divided powder. The rationale behind its use in acute nonspecific diarrhea stems from its ability to adsorb some of the bacterial toxins that often cause the condition. It is almost harmless and is effective in many cases of diarrhea if taken in large enough doses (2-10 g initially, followed by the same amount after every bowel movement). The adsorbents are generally safe, but they may interfere with the absorption of some drugs from the GI tract. 

Absorbents, such as kaolin (a hydrated aluminum silicate clay mineral), pectin (a complex carbohydrate often extracted from fruits), and atta-pulgite (a hydrated magnesium aluminum silicate clay mineral), form a thickening powder that absorbs excess fluid and any bacterial toxins present (action of kaolin and attapulgite) and increases the consistency of the stool by forming a viscous colloidal solution (action of pectin). However, these agents may also absorb essential body enzymes and nutrients. 

Furda (28) illustrates this postulation in a simplified model (Figure 5) where several hypothetical situations are shown. In the first case Fe2+ nearly neutralizes the fiber leaving a net positive charge of +3, in the second and third cases, Fe3+, the trivalent ion produces a net positive charge of +6 and +15 respectively. He explains the greater affinity of fatty acid to the ferric-pectin complex rather than to aluminum-pectin complex by the possibility of different size cations or by the hydrophilicity of the aluminum cation, but cautions that these explanations require further research. 

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