Effect of supromolecular interactions with cationic surfactant decamethoxine on adsorption of curcumine on highly dispersed silica

Curcumin, a sparingly soluble polyphenol of plant origin, has antitumor, anti-inflammatory, antithrombotic, antidiabetic and antimicrobial properties. Currently, an important task is the development of medicinal composites based on curcumin, which provide an increase in its solubility and, accordingly, bioavailability. The aim of the work is to determine the optimal conditions for the adsorption of curcumin on the surface of a silica enterosorbent as soluble supramolecular complexes with a cationic dimeric surfactant decamethoxine. The UV/Vis spectroscopy data indicate that supramolecular interactions with decamethoxine lead to changes in the spectral characteristics of curcumin in solutions and on silica surface. The bathochromic shift of the absorption spectrum of curcumin in decamethoxine solutions characterizes the polarization of its carbonyl group in supramolecular complexes. The hypsochromic shift in the absorption spectra of curcumin adsorbed from decamethoxine solutions on silica is explained by the violation of its conjugated π-bond system, resulted probably from the change in the spatial orientation of the curcumin molecule at the adsorption of its complexes on the sorbent surface. Curcumin is adsorbed on highly dispersed silica much more effectively from decamethoxine solutions than from aqueous solutions. The adsorption of curcumin is maximal (92 %) at a concentration of decamethoxine 0.002 M, and decreases sharply to 9 % in the micellar region of concentrations (≥ 0.008 M). The dependence of curcumin adsorption on decamethoxine concentration is described by a domed curve, which indicates a significant contribution of hydrophobic interactions to the formation of supramolecular complexes of curcumin with cationic surfactant and their adsorption on silica surface. The results obtained are of practical importance and can be used in the development of new, more effective medicines containing bioactive curcumin, antiseptic decamethoxine and silica enterosorbent.