Cyclodextrin - Essential Oil Complexes Studied by Thermal Gravimetry Analysis - Differential Scanning Calorimetry

Abstract

Background: The structural features allow cyclodextrins to form solid inclusion complexes (host–guest complexes) with wide variety of solid, liquid, and gaseous compounds as a guest. It is the utmost an astounding property of the cyclodextrins, and is commonly termed as molecular recognition. The process of formation of an inclusion complex of the cyclodextrins has been associated with the substitution of the water inside the hydrophobic cavity and the non–covalent bonding interactions of the guest in the hydrophobic host cavity. Objective: To study the thermal gravimetry analysis behaviour for α–cyclodextrin–clove oil, α–cyclodextrin–neem oil and β–cyclodextrin–clove oil adducts using TGA–DSC. : To compute specific heat capacity at constant pressure, as a function of temperature for the studied systems. Methods: The thermal gravimetry analysis and differential scanning calorimetry techniques are used. Results: It is observed that the calculated Cp values from DSC curves are of low magnitude for α–CD–neem oil adduct as compared to that of individual constituents over the temperature range studied. An interesting pattern for the Cp values is found to emerge in case of α– CD–clove oil and β–CD–clove oil adducts wherein the calculated Cp values are higher in magnitude than for pure clove oil but are lower than that of the pure cyclodextrins. Conclusion: Using thermal methods, the attempt to understand the possibilities of molecular complex formation between cyclodextrins and medicinally important neem oil and clove oil is described. The crystals of inclusion compounds for clove oil and neem oil with α–CD and β–CD are synthesized. The results of TGA–DSC for the crystals are presented and analysed. Other: The results of neem oil–adducts have been explained in terms of binding of part of tri–glyceride linkages by 2–3 cyclodextrin molecules as neem oil is tri–glyceride and the adduct is having lower stability.