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Development of an Assay to Determine the Amount of Ca-Fatty Acid Soaps in Feces
Natascha Stroebinger1, Shane M Rutherfurd1, Sharon J Henare1
1Riddet Institute, Massey University, Palmerston North 4442, New Zealand.
Background:
The quantification of fecal Ca-fatty acid soaps is important to understand how fatty acids behave in the gastrointestinal tract.
Objective:
As current methods to extract Ca-fatty acid soaps from feces give low recoveries an accurate assay to determine the amount of fatty acid soaps in feces was developed.
Method:
Ca-fatty acid soaps are determined indirectly after non-soap fatty acid compounds have been extracted from the feces. Synthetic Ca-fatty acid soaps of different chain lengths (C12-C18) and degree of saturation (C18:0-C18:2) were incubated with several solvents to find the solvents that least-solubilize the Ca-fatty acid soaps. A three-step extraction was devised using extractions with hexane, hexane-isopropanol and water either at room temperature or at 60°C, 37°C, or 80°C, respectively. Feces were spiked with free fatty acids, Ca-fatty acid soaps, Na-fatty acid salts, and phospholipids.
Results:
All of the free fatty acids and phospholipids and almost all of the Na-fatty acid salts were removed and 98% of Ca-lauric acid soap, 99% of Ca-stearic acid soap, and 93% of oleic acid soap were recovered.
Conclusions:
The method is suitable for determining fatty acids in the form of Ca-fatty acid soaps in feces.
Highlights:
New method to determine fecal Ca-fatty acid soaps. Consistent and high recovery of fatty acid-soaps.
