Alkyl Ethoxylated and Alkylphenol Ethoxylated Nonionic Surfactants: Interaction with Bioactive Compounds and Biological Effects

Nonionic surfactants are amphipathic molecules consisting of a hydrophobic (alkylated phenol derivatives, fatty acids, longchain linear alcohols, etc.) and a hydrophilic part (generally ethylene oxide chains of various length). Although not as important commercially, tertiary amine and various sugar surfactants are also nonionic surfactants. Due to their favorable physicochemical properties, nonionic surfactants are extensively used in many fields of technology and research. The application of nonionic surfactants in various biotechnological processes has been recently reviewed (1). Surfactants have been successfully used to decrease the foaming of fermentation broths during solvent extraction (2), increase the conversion of linoleic acid to its hydroperoxide (3), and enhance the rate of cellulose hydrolysis (4). Nonionic surfactants are an integral part of the majority of pesticide formulations (5). They increase the leaf retention of spray solutions (6), enhance adhesional forces of aqueous droplets on crop leaf surfaces (7), and generally improve the effectiveness of active ingredients (8,9). However, not only do surfactants influence the performance of pesticides, but the pesticides exert some effects on the fate of surfactants; for example, pesticides promote or inhibit the photolytic degradation of nonionic surfactants (10). Nonionic surfactants are also used in pharmaceuticals to increase their stability (11) and to enhance the dissolution rate of active ingredients from suppositories (12) and solid dispersions (13), for example. The pharmaceutical industry also uses nonionic surfactants to facilitate solubilization (14) and to increase the stability of drugcarrier emulsions (15). Surfactants markedly modify the particle size of precipitated drugs, too (16,17. Due to strict regulations, nonionic surfactants have only limited application in the food industry, where they are employed to change the stability of various emulsions (18) and to decrease the retrogradation of amylopectin (19). Nonionic surfactants also have been used in analytical chemistry to increase the fluorescence of dansylated amino acids (20), improve protein separation in capillary zone electrophoresis (21), and mask side effects in spectrophotometry (22). This review presents a critical evaluation of recent results of studies on the interaction of alkyl ethoxylated and alkylphenol ethoxylated nonionic surfactants with various bioactive macromolecules and with organisms. The fate of surfactants in various ecological systems has been extensively studied. Nonionic surfactants are generally easily degradable; however, in some cases the persistence of intermediates has been observed. Due to the limited scope of this review, investigations of intermediates will not be discussed in detail.