As a measure of a lipophilicity, the octanol-water partition coefficient (KOW) makes it possible to estimate the interaction of a chemical compound with a variety of biological interfaces. For example, there is a correlation between the values of log KOW and skin permeability coefficient (Kp)a parameter describing the ability of an active ingredient to penetrate the skin, which is important for the design of new active pharmaceutical ingredients . It is also possible to estimate the bioavailability of new pesticides based on their log KOW value . In addition, log KOW is useful in predicting the environmental fate of new for the increased lipophilicity of compounds 3Br, 3Asp, and 3Ala, even despite the presence of a highly hydrophilic amino acid-derived anion in the case of the latter two. In contrast, compounds with a short butyl substituent show significant hydrophilicity (log KOW < -0.5). The introduction of a hydroxyl group into the short alkyl chain does not increase the hydrophilicity of 4Br compared to 1Br, although both 4Asp and 4Ala are characterized by lower log KOW values (-1.18 and -1.34, respectively) compared to 1Asp (-0.91) and 1Ala (-0.90). In all analyzed cases, the exchange of the bromide anion for the proteinogenic amino acid anion resulted in a significant reduction in log KOW. It should also be noted that quinine-based QASs have significantly higher hydrophilicity compared to quinine free base (log KOW = 3.44) . This phenomenon confirms that the strategy of transferring biologically active substances into an ionic form with favorable properties can improve their hydrophilicity and bioavailability .