Preparation and characterization of [6]-gingerol/β-cyclodextrin inclusion complexes

Six-gingerol, the most abundant secondary metabolite present in ginger oleoresin, is a bioactive compound with antioxidant, anti-inflammatory and anticancer activities. This compound presented great cytotoxic potential in several cancer cell lines, and an increment in its activity can be achieved through complexation with cyclodextrins. In addition, the 6G complexation can modify its physical state from liquid to solid and mask its pungent taste, unpleasant for some people. The [6]-gingerol/β-cyclodextrin binary inclusion complex (6G/βCD) and [6]-gingerol/β-cyclodextrin/chitosan (6G/βCD/chitosan) ternary inclusion complex were successfully prepared in the solid state with the coprecipitation method, and characterized by 1D and 2D Nuclear Magnetic Nuclear, Fourier transform-infrared spectroscopy, Differential Scanning Calorimetry, Scanning Electronic Microscopy and Molecular Modelling Studies. Analysis of phase solubility indicated that the inclusion complexes presented a B-type curve and stability constant values suitable for practical applications. NMR analysis, dissolution test and molecular modelling indicated that 6G can form total 1:2 inclusion complex with βCD, with the aromatic ring and alkyl chain of 6G located in the narrow side of the hydrophobic cavity of the two βCDs. The dissolution test showed a faster dissolution for inclusion complexes when compared to free 6G. Furthermore, the cytotoxicity activity of the 6G/βCD binary inclusion complex was examined to determine whether the bioactivities of 6G were affected by its inclusion. The cytotoxicity assays revealed that 6G/βCD had a slightly higher bioactivity than the free 6G, corroborating the slight increase in the solubility of 6G in the inclusion complex.