The presence of palmitic acid in the aqueous fraction of a hydroethanolic extract can be attributed to several mechanisms. These may include micelle formation, salt formation in slightly basic conditions, residual co-solvent effects from ethanol, emulsion formation, or complexation with other water-soluble compounds. The specific combination of these mechanisms likely depends on the extract's pH, temperature, and overall composition.
Dear Dr.Abdelhak Maghchiche
Thanks for the response.
It possesses amphillic property but the hydroethanolic extract was passed through a sequence of solvents hexane, chloroform, ethyl acetate, n butanol and aqueous. So my question is even though palmitic acid is more soluble in non-polar it will not be completely removed by any individual solvent and thus will be extracted in the aqueous fraction also.
The presence of palmitic acid in the aqueous fraction of a hydroethanolic extract, despite its known preference for non-polar solvents, can be attributed to several factors related to its amphiphilic nature and the solvent extraction process used.
Palmitic acid is a saturated fatty acid with a long hydrocarbon chain that is largely hydrophobic, making it more soluble in non-polar solvents such as hexane or chloroform. However, the carboxylic acid functional group (-COOH) at one end of the molecule is polar, giving palmitic acid amphiphilic properties. This amphiphilic characteristic allows it to interact with both polar and non-polar environments to some extent.
During the sequential solvent extraction process, the hydroethanolic extract is subjected to a series of solvents with varying polarities: hexane, chloroform, ethyl acetate, n-butanol, and finally water. While palmitic acid is primarily non-polar and would preferentially dissolve in hexane and chloroform, it is unlikely that it would be completely removed by these solvents. This incomplete removal can be attributed to several reasons.
Firstly, solvent extraction is rarely perfectly selective, meaning that even non-polar compounds like palmitic acid can partially partition into more polar phases, especially when they possess polar functional groups. The polar carboxylic acid group in palmitic acid allows for some solubility in more polar solvents like n-butanol and water, although this solubility is relatively low.
Secondly, the process of solvent extraction is often influenced by the concentration of the compound, the volume and type of solvent used, and the number of extraction cycles. Even if the majority of palmitic acid is extracted into the non-polar solvents during the initial stages, residual amounts can remain and be carried over into subsequent fractions.
Finally, the interaction of palmitic acid with other compounds in the extract, such as proteins, polysaccharides, or other amphiphilic molecules, could lead to the formation of micelles or complexes that increase its apparent solubility in the aqueous phase. These interactions can trap palmitic acid within the aqueous fraction, even though it is not the solvent in which it is most soluble under normal conditions.
Dear Phil Kading,
Thank you for your reply. We got clarity for the doubts.
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