Characterization of cyclodextrin complexes with turmeric oleoresin

Turmeric rhizome oleoresin (TRO) was successfully solubilised in aqueous solution by forming inclusion complexes with β-cyclodextrin (BCD) and γ-cyclodextrin (GCD). To investigate molecular associations of BCD and/or GCD with the oleoresin, phase solubility studies were undertaken, using 1,8-cineole (C10H18O) and ar-tumerone (C15H20O) as marker compounds to represent turmeric oleoresin. In the presence of cyclodextrins, the solubility of 1,8-cineole and ar-tumerone were enhanced. Based on the stability constant, k1:1, the GCD-complex was at least twice effective than BCD. Solid state inclusion complexes were also prepared, using kneading (K) and co-precipitation (CP) methods, and analysed using Fourier transform infrared (FTIR) spectrometry and scanning electron microscopy (SEM). The shift of CO stretching to higher wavenumbers and strengthening of the CO stretching band indicated the formation of a complex between CD and TRO. The new solid phase formed using the co-precipitation method, had a crystal structure which was completely different from the original morphology of oleoresin and cyclodextrins.