Temperature-dependent stability and DPPH scavenging activity of liposomal curcumin at pH 7.0.

This paper investigated the influences of temperature on the stability and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of curcumin encapsulated in liposome at pH 7.0. Liposomal curcumin showed higher stability and DPPH scavenging activity than free curcumin at 25°C. When temperature increased from 25 to 80°C, liposomal curcumin degraded more pronouncedly above the phase transition temperature (T(m)=45.7°C) of liposome than lower temperatures, suggesting a weaker curcumin protection from the liquid crystalline phase of phospholipid bilayer than that from the gel phase. Moreover, the presence of remarkable "jump" increases around T(m) in the values of observed pseudo-first-order rate constant and the percent of DPPH scavenging activity of liposomal curcumin indicated that the liquid crystalline phase of phospholipid bilayer is more beneficial for curcumin to reduce DPPH. This study reveals that changing the microstructure of encapsulation carrier may effectively control the properties of phytochemicals like curcumin.