Abstract
Using choline as a counterion in fatty acid surfactants substantially increases their H2O soly. as compared to classical Na and K soaps, and thereby enables the application of desirable longer-chain derivs. at ambient temp. Since choline can be decompd. both physiol. and environmentally, corresponding fatty acid soaps are considered to be highly biocompatible. Recent toxicity and ...
Abstract
Using choline as a counterion in fatty acid surfactants substantially increases their H2O soly. as compared to classical Na and K soaps, and thereby enables the application of desirable longer-chain derivs. at ambient temp. Since choline can be decompd. both physiol. and environmentally, corresponding fatty acid soaps are considered to be highly biocompatible. Recent toxicity and biodegradability studies of choline ionic liqs., including anions such as short- and middle-chain alkanoates, have verified the expected low toxic impact. However, according to the European Cosmetic Directive 76/768/EEC, all salts of choline are forbidden in cosmetic products, mainly just due to its classification as a quaternary ammonium ion. To facilitate their application in the future, the authors have studied the biodegradability of choline soaps (ChCm) with alkyl chain lengths of m = 12-18 according to the OCDE 301F std. Further, the cytotoxicity of ChCm surfactants with m = 8-16 was detd., both for odd- and even-numbered fatty acids. Studies were carried out using 2 different human cell lines, cervix carcinoma cells (HeLa) and keratinocytes (SK-Mel-28). For a better comparability to common soaps and to shed light on the influence of the cation, Na and K homologs were also studied. Results reveal an unexpected nonlinear relation between the hydrophobic chain length and the IC50 value. Most importantly, the presented data show that IC50 values of ChCm surfactants coincide with those of the widely applied Na and K soaps. This demonstrates that choline carboxylate surfactants are harmless and thus strongly supports their applicability in customer end products. [on SciFinder(R)]
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