Green silver nanoparticle and Tween-20 modulated pro-oxidant to antioxidant curcumin transformation in aqueous CTAB stabilized peanut oil emulsions

This study reports the preparation, characterization and in vitro antioxidant activity of curcumin (curc) encapsulated oil-in-water (o/w) nano and micro emulsions. Formulations for curc loading were made via room temperature (RT) stirring, using peanut oil with cetyltrimethylammonium bromide (CTAB, cationic surfactant), 1:1 and 1:3 (CTAB + Tween-20 (Tw-20)) molal stoichiometries. Besides these combinations, 1:1 mixtures of CTAB formulations and Tw-20 dispersed Syzygium cumini leaf extract capped Ag nanoparticles, were also made. Ethanol and glycerol were included as co-solvent and cosurfactant to equilibrate the hydrophilic and hydrophobic proximities. Amongst all combinations, the CTAB caused weakest curc dispersion indicated by (839.91-2452.58) nm sizes and abysmal (21.80-53.90)% 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activities (FRSA). Contrary to this, the (CTAB + Tw-20) and 1:1 mixtures with Tw-20 dispersed Ag NPs displayed finer curc dispersion inferred via (9.30-60.35)%, (12.34-70.53), (59.47-73.09)% size decrements and (103.88-298.30), (85.51-206.44), (59.28-265.08)% FRSA increments. The findings are supported by (1.643-10.381)% surface tension (eta) increments and (4.0161-14.367)% viscosity (gamma) decrements compared to CTAB formulations, depicting binding force (BF) moderation enabled >100% FRSA enhancements. Dispersion variations of curc with (CTAB + Tw-20) and Tw-20 dispersed Ag NPs moderated the CTAB N+ - and Br- hydration sphere activities, facilitating enhanced thermodynamic stability through a progressive replacement of stronger Columbic electrostatic forces by hydrophobic-hydrophilic, hydrophilic-hydrophilic, van der Waal and hydrogen bonded interactions. (C) 2019 Elsevier B.V. All rights reserved.