Unravelling the nature of intra-molecular hydrogen bonds in curcumin using in-situ low temperature spectroscopic studies

Aromas: Lovely to Smell and Nice Solvents for Polyphenols? Curcumin Solubilisation Power of Fragrances and Flavours

Natural aromas like cinnamaldehyde are suitable solvents to extract curcuminoids, the active ingredients found in the rhizomes of Curcuma longa L. In a pursuit to find other nature-based solvents, capable of solving curcumin, forty fragrances and flavours were investigated in terms of their solubilisation power. Aroma compounds were selected according to their molecular structure and functional groups. Their capabilities of solving curcumin were examined by UV-Vis spectroscopy and COSMO-RS calculations. The trends of these calculations were in accordance with the experimental solubilisation trend of the solubility screening and a list with the respective curcumin concentrations is given; σ-profiles and Gibbs free energy were considered to further investigate the solubilisation process of curcumin, which was found to be based on hydrogen bonding. High curcumin solubility was achieved in the presence of solvent (mixtures) with high hydrogen-bond-acceptor and low hydrogen-bond-donor abilities, like γ- and δ-lactones. The special case of DMSO was also examined, as the highest curcumin solubility was observed with it. Possible specific interactions of selected aroma compounds (citral and δ-hexalactone) with curcumin were investigated via 1H NMR and NOESY experiments. The tested flavours and fragrances were evaluated regarding their potential as green alternative solvents.

Curcumin Accelerates the Lateral Motion of DPPC Membranes

Curcumin, the main ingredient in turmeric, has attracted attention due to its potential anti-inflammatory, anticancer, wound-healing, and antioxidant properties. Though curcumin efficacy is related to its interaction with biomembranes, there are few reports on the effects of curcumin on the lateral motion of lipids, a fundamental process in the cell membrane. Employing the quasielastic neutron scattering technique, we explore the effects of curcumin on the lateral diffusion of the dipalmotylphosphatidylcholine (DPPC) membrane. Our investigation is also supported by Fourier transform infrared spectroscopy, dynamic light scattering, and calorimetry to understand the interaction between curcumin and the DPPC membrane. It is found that curcumin significantly modulates the packing arrangement and conformations of DPPC lipid, leading to enhanced membrane dynamics. In particular, we find that the presence of curcumin substantially accelerates the DPPC lateral motion in both ordered and fluid phases. The effects are more pronounced in the ordered phase where the lateral diffusion coefficient increases by 23% in comparison to 9% in the fluid phase. Our measurements provide critical insights into molecular mechanisms underlying increased lateral diffusion. In contrast, the localized internal motions of DPPC are barely altered, except for a marginal enhancement observed in the ordered phase. In essence, these findings indicate that curcumin is favorably located at the membrane interface rather than in a transbilayer configuration. Further, the unambiguous evidence that curcumin modulates the membrane dynamics at a molecular level supports a possible action mechanism in which curcumin can act as an allosteric regulator of membrane functionality.

Influence of molecular interactions on structure, controlled release and cytotoxicity of curcumin encapsulated chitosan - Silica nanostructured microspheres

Curcumin possesses numerous medicinal benefits including anti-cancer and anti-viral properties. However, its wide scale use as a drug is often hindered owing to the dearth of suitable drug-delivery systems which can solubilise it for long-term sustained-release and safeguard its beneficial properties. In this work, a fast, one-step method, employing evaporation induced assembly of colloids, has been employed for the synthesis of curcumin encapsulated organic-inorganic hybrid micron-sized spheres. Detailed physical properties of the microspheres, with scaffolds of silica nanoparticles (∼8.5 nm) cross linked by chitosan, are studied to trace the underlying mechanism of structural assembly in such systems, by tuning the polymer matrix with solubilizing agents, DMSO and Tween 20. A systematic modification in the hydrogen bonding network, conformations and interactions between macromolecules is revealed upon tuning the organic matrix. This in turn is found to control the assembly vis-à-vis the granular morphology, drug entrapment and packing fraction of nanoparticles in the microspheres, which have direct influence on the biological properties. Consequently, the microspheres are found to follow a first order drug release kinetics with a tunable rate constant which follows the ordering of packing fraction of silica nanoparticles in the micro-granules. A sustained curcumin release for a period extending up to 24 h has been achieved. Further studies using human lung and cervical cancer cell lines assert good anti-cancer properties of these nanostructured microspheres in cancer cells, while showing no toxicity towards normal cells. Thus, such hybrid organic-inorganic formulations achieved using multi-component colloidal assembly approach, with enhanced stability against degradation, are promising candidates for future clinical applications of water-insoluble drugs.