Artificial intestinal juice

A stability-indicating HPLC method has been described for niclosamide in artificial gastric and intestinal juices [68],... 

Rodriguez et al. [68] studied the stability of niclosamide in artificial gastric and intestinal juices. The gastric juice contained sodium chloride and hydrochloric acid with or without pepsin. The intestinal juice contained sodium phosphate with or without pancreatin. Niclosamide was incubated with the juices at 37°C for 6 h. The remaining intact drug and its degradation products (2-chloro-4-nitroaniline, 5-chlorosalicylic acid) were extracted with chloroform/methanol (5 1) and determined by TLC and HPLC. The drug was stable in these media for at least for 6 h. 

In vitro experiments have shown that cyclotetraglucose dissolved in Bis-Tris buffer (50 mmol/l) is not degraded by human salivary or porcine pancreatic a-amylase or by artificial gastric juice (pH 2). Only 0.7% of cyclotetraglucose incurred ring opening during a 3-h incubation period with an acetone powder preparation of the rat intestinal mucosa to form a linear tetrasaccharide (Hashimoto et al., 2006). 

Scheme 98.1 Chamazulene (26) fonnation from matricin (3). Thermally, the reaction runs to 26, whereas a reaction induced in artificial gastric or intestinal juice stops at 25. Intermediates 23 and 24 are hypothetical.

An example of a nonoccupational exposure is methanol, which is formed endogenously, probably as the result of the activities of intestinal flora or enzymatic processes. It is present in a number of consumer products. Methanol may be present in low concentrations in some foods, juices, and alcoholic beverages. Methanol can also be derived from the intestinal enzymatic hydrolysis of the artificial sweetener aspartame, which results in methanol absorption from the intestine (Butchko et al. 2002). It is estimated that a 355-mL serving of aspartame-sweetened beverages and of various fruit and tomato juices may contribute about 20-100 mg of dietary methanol (Butchko et al. 2002). For comparison purposes, exposure at the current Threshold Limit Value time-weighted average of methanol (262 mg/m3) would result in a daily dose of about 1,500 mg, assuming an 8-hour inhaled volume of 10 m3 of air and absorption of 57%. 

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