The Aggregation Behavior and Antioxidative Activity of Amphiphilic Surfactants Based on Quinuclidin‐3‐ol

The self-aggregation and thermodynamic properties of three cationic surfactants as quaternary ammonium salts have been investigated. The physicochemical properties of compounds containing quinuclidin-3-ol with even-number of carbon atoms (10, 12 and 14) in the hydrophobic tail were measured by conductivity, dynamic light scattering (DLS) and Zeta-potential measurements. DLS and Zeta- potential measurements show similar size distribution for all surfactants with excellent uniformity, and Zeta-potential increases significantly with increase in the size of hydrocarbon tail. The critical micellar concentration (c.m.c.) and the degree of micelle ionization () were determined using conductivity measurements. The c.m.c. values of surfactants were found to be between 3.4 to 23.8.10-3 M. The standard Gibbs free energy (∆G_mic^o) was derived from conductivity measurements and suggests that surfactants containing longer chains spontaneously form micelles. The antioxidative properties of these cationic surfactants were evaluated using the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC) assays. Among tested samples, N-tetradecyl-3- hydroxyquinuclidinium bromide (QOH-C14) exhibited the highest antioxidative potential (388.30 nmol (TE) equivalents mL-1), which was further investigated by the DNA nicking assay.