Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide, F-59000 Lille, France.
J Colloid Interface Sci. 2018 Feb 1;511:165-173. doi: 10.1016/j.jcis.2017.09.096. Epub 2017 Sep 28.
In contrast to anionic and nonionic amphiphilic substances, bio-based cationic ones are very rare. Cationic amphiphiles are mostly based on quaternary ammonium, pyridinium or imidazolium groups that are either badly biodegradable or have toxic residues even after degradation. In the search for green alternatives to cationic hydrotropes and amphiphiles, natural l-carnitine could be a promising candidate for a cationic headgroup.
By esterification of carnitine in one step and with low cost, cationic molecules with alkyl chain length of n=2-14 could be obtained. Their thermal properties, aggregation behaviour and cytotoxicity were determined. Hydrophobic compounds were solubilized in their aqueous solutions and the PIT-slope method was applied to determine a relative hydrophilicity.
It was found that some pure carnitine ester bromides were liquid at room temperature and thus can be classified as ionic liquids. They are highly water-soluble, and in aqueous solutions, they showed hydrotrope or surfactant behaviour depending on their alkyl chain length. Their high hydrotropic efficiency was demonstrated by solubilizing Disperse Red 13, while also biomolecules, like vanillin, could be dissolved in reasonable amounts. In all tests, they performed at least as good as the tested reference substances, while showing similar cytotoxicity towards human skin keratinocytes, thus demonstrating their potential as green functional amphiphilic molecules of positive charge.
与阴离子型和非离子型两亲物质相比，生物基阳离子型两亲物质非常罕见。阳离子两亲物大多基于季铵、吡啶或咪唑基团，这些基团要么生物降解性差，要么即使在降解后仍有有毒残留物。在寻找阳离子增溶剂和两亲物的绿色替代品时，天然左旋肉碱可能是阳离子头基的有前途的候选物。
通过一步酯化和低成本，可以获得具有烷基链长 n=2-14 的阳离子分子。测定了它们的热性能、聚集行为和细胞毒性。疏水性化合物在其水溶液中溶解，并应用 PIT 斜率法来确定相对亲水性。
发现一些纯肉碱酯溴化物在室温下为液态，因此可以归类为离子液体。它们具有高水溶性，在水溶液中，根据其烷基链长，它们表现出增溶或表面活性剂行为。它们的高增溶效率通过溶解分散红 13 得到证明，同时也可以溶解相当数量的生物分子，如香草醛。在所有测试中，它们的性能至少与测试的参考物质一样好，同时对人皮肤角质形成细胞的细胞毒性相似，因此证明了它们作为带正电荷的绿色功能性两亲分子的潜力。
