calixarenes and caffeic-acid

In this work the inclusion complex formation of Caffeic acid (CA) with p-sulfonatocalix[n]arenes (SCXn, n=4, 6, 8) is reported aiming to improve the antioxidant activity, thermal stability and photostability properties of CA. Evidence for the formation was obtained using fluorescence spectroscopy, nuclear magnetic resonance spectroscopy (NMR), pulsed field gradient NMR (PFG-NMR), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and scanning electron microphotographs (SEM). Experimental conditions including concentrations of SCXn and pH were investigated for the inclusion formation in detail. The results showed that CA was able to form inclusion complexes with SCXn in a molar ratio of 1:1, and the formation constants were varied with the pH conditions. NMR spectroscopy indicated that both the aromatic ring and the vinyl group of CA were partially covered by SCXn.

Topics: Antioxidants; Biphenyl Compounds; Caffeic Acids; Calixarenes; Calorimetry, Differential Scanning; Free Radical Scavengers; Hydrogen-Ion Concentration; Microscopy, Electron, Scanning; Picrates; Proton Magnetic Resonance Spectroscopy; Solutions; Spectrometry, Fluorescence; Spectroscopy, Fourier Transform Infrared; Temperature; Time Factors