Spirulina sp. LEB 18-extracted phycocyanin: Effects on liposomes' physicochemical parameters and correlation with antiradical/antioxidant properties.

This study describes the physicochemical properties of soybean asolectin (ASO) liposomes loaded with phycocyanin (Phy) extracted from Spirulina sp. LEB 18. The effects of Phy in the liposomes' properties were investigated by Fourier transform infrared spectroscopy (FTIR), 1H and 31P nuclear magnetic resonance (NMR), zeta (ζ)-potential, dynamic light scattering (DLS) and ultraviolet-visible (UV-vis) techniques. Phy restricted the motion of ASO polar and interface groups and disrupted the package arrangement of the lipid hydrophobic regions, as a likely effect of dipolar and π interactions related to its amino acid residues and pyrrole portions. These interactions were correlated to antiradical/antioxidant Phy responses obtained by 2,2-diphenyl-1-picrylhidrazil (DPPH) assay, thiobarbituric acid reactive substances (TBARS) and ferric reducing antioxidant power (FRAP) methods, and discussed to bring new chemical perspectives about Phy-loaded liposomes-related nutraceutical applications in inflammatory and viral infection processes.

Effects of α-eleostearic acid on asolectin liposomes dynamics: relevance to its antioxidant activity.

In this study, the effect of α-eleostearic acid (α-ESA) on the lipid peroxidation of soybean asolectin (ASO) liposomes was investigated. This effect was correlated to changes caused by the fatty acid in the membrane dynamics. The influence of α-ESA on the dynamic properties of liposomes, such as hydration, mobility and order, were followed by horizontal attenuated total reflection Fourier transform infrared spectroscopy (HATR-FTIR), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and UV-vis techniques. The α-ESA showed an in vitro antioxidant activity against the damage induced by hydroxyl radical (OH) in ASO liposomes. The analysis of HATR-FTIR frequency shifts and bandwidths and (1)H NMR spin-lattice relaxation times, related to specific lipid groups, showed that α-ESA causes an ordering effect on the polar and interfacial regions of ASO liposomes, which may restrict the OH diffusion in the membrane. The DSC enthalpy variation analysis suggested that the fatty acid promoted a disordering effect on lipid hydrophobic regions, which may facilitate interactions between the reactive specie and α-ESA. Turbidity results showed that α-ESA induces a global disordering effect on ASO liposomes, which may be attributed to a change in the lipid geometry and shape. Results of this study may allow a more complete view of α-ESA antioxidant mode of action against OH, considering its influence on the membrane dynamics.