Antioxidant activity of vitamin E enhanced by cyclodextrin inclusion complex

Abstract

PurposeThe study aims to find potential method to enhance the stability and antioxidant activity of vitamins.Design/methodology/approachVitamin E (VE) and β-cyclodextrin (CD) were used to prepare the VE-β-CD inclusion complex via a solution method. The yielded VE-β-CD obtained from optimal experimental conditions was characterized. The mechanism of complex formation and the properties of the complex was investigated by steady-state and time-resolved fluorescence techniques. The antioxidant activity of VE-β-CD was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and compared with pure VE.FindingsThree experimental factors – reaction temperature (T), molar ratio of VE to β-CD (rm) and inclusion time (t) – were studied for the preparation of VE-β-CD. At experimental conditions of T = 60°C, rm = 1:3 and t = 3 h, a maximum inclusion rate of VE (78.62%) was obtained. The Fourier-transform infrared spectroscopy (FTIR) shows that VE molecule was physically encapsulated by β-CD in the yielded product. Subsequentially, the steady-state fluorescence intensity of VE was found to increase upon encapsulation by β-CD due to the hindrance of fluorescence quenching of VE molecules inside the hydrophobic cavity of β-CD, and an inclusion constant K was determined to equal 3.58 × 103 L/mol from the fluorescence results. The fluorescent observation was confirmed by time-resolved fluorescence experiment as the lifetime of VE increased with an increase in β-CD concentration.Originality/valueThe ability of removing radicals by VE was significantly enhanced after the formation of inclusion complex with β-CD.