The purpose of this study was to investigate the potential of a saponin-rich extract of Quillaja saponaria to replace bile salts in the surfactant formulations for stabilization of nanostructured lipid carriers (NLC). The influence of Quillaja extract and/or high-melting lecithin at different concentrations on physical and oxidative stability was evaluated in (i) NLC containing tristearin and ω-3 fish oil, (ii) ω-3 fish oil-in-water emulsion, and (iii) solid lipid nanoparticles (SLN) containing tristearin. Best physical, polymorphic and oxidative stability of NLC were achieved with a surfactant combination of 2.4% (w/w) Quillaja extract and 0.6% (w/w) high-melting lecithin. The results showed that encapsulation of ω-3 fish oil into NLC inhibited the formation of lipid hydroperoxides, propanal and hexanal by 72, 53 and 57%, respectively, compared to the fish oil-in-water emulsion prepared with the same surfactants. This indicated that the low oxidation observed in NLC cannot be due to potential antioxidative effects of the surfactant combination itself. Evidence is accumulating that tristearin is able to form a protective shell around the ω-3 fish oil, when crystallization is induced via high-melting phospholipids in the solidified interfacial layer.
Keywords: Crystallization; Lipid oxidation; Nanostructured lipid carriers; Polymorphic transition; Quillaja saponins; Solid lipid nanoparticles.
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