The interaction between the hydrophobic indolinonic nitroxide radical, 1,2-dihydro-2-methyl-2-phenyl-3H-indole-3-one-1-oxyl and hydrophilic α-, β- and γ-cyclodextrin derivatives was investigated in water by phase-solubility analysis. Among the studied cyclodextrins, random methyl-β-cyclodextrin (RM-β-CD) had the greatest solubilizing activity (1312-fold increase in the intrinsic aqueous solubility). Solid complexes were prepared by the freeze-drying method and characterized by powder X-ray diffractometry and thermal analysis. Complexation of the nitroxide with RM-β-CD was also confirmed in solution by electron paramagnetic resonance (EPR) spectroscopy. Photodegradation of the nitroxide was reduced by complexation with RM-β-CD, this effect being more pronounced in the solid-state (the extent of degradation was 28.0% for the complex vs. 78.8% for uncomplexed nitroxide) than in solution (41.2 vs. 69.1% for uncomplexed nitroxide). The antioxidant activity of the complex was also investigat...
Effect of complexation with randomly methylated beta-cyclodextrin on the aqueous solubility, photostability and antioxidant activity of an indolinonic nitroxide radical
SCALIA, Santo
2005
Abstract
The interaction between the hydrophobic indolinonic nitroxide radical, 1,2-dihydro-2-methyl-2-phenyl-3H-indole-3-one-1-oxyl and hydrophilic α-, β- and γ-cyclodextrin derivatives was investigated in water by phase-solubility analysis. Among the studied cyclodextrins, random methyl-β-cyclodextrin (RM-β-CD) had the greatest solubilizing activity (1312-fold increase in the intrinsic aqueous solubility). Solid complexes were prepared by the freeze-drying method and characterized by powder X-ray diffractometry and thermal analysis. Complexation of the nitroxide with RM-β-CD was also confirmed in solution by electron paramagnetic resonance (EPR) spectroscopy. Photodegradation of the nitroxide was reduced by complexation with RM-β-CD, this effect being more pronounced in the solid-state (the extent of degradation was 28.0% for the complex vs. 78.8% for uncomplexed nitroxide) than in solution (41.2 vs. 69.1% for uncomplexed nitroxide). The antioxidant activity of the complex was also investigat...I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
