Interaction of Bisdemethoxycurcumin with Sodium Dodecyl Sarcosine + Tween 20/tween 60 Mixed Surfactants: Insights from Multispectral Analysis and Solubilization Effect

The low aqueous solubility of curcuminoids, including bisdemethoxycurcumin (BDMC), severely limits their applications in the food and pharmaceutical industries. This improvement is expected to be achieved by encapsulating them with mixed surfactant micellar systems. In this study, the interaction of BDMC with sodium dodecyl sarcosine (SDDS) + Tween 20/Tween 60 mixed micelles was studied at the molecular level. The molar ratio of Tween 20/Tween 60 to SDDS in the mixed micelles was optimized using response surface methodology. The binding parameters of BDMC to the mixed micelles were determined by fluorescence and UV–vis absorption spectroscopy. Thermodynamic analysis showed that the hydrophobic interaction was dominant in the binding process. The longer hydrophobic chain of Tween 60 was responsible for the stronger interaction of BDMC with SDDS + Tween 60. The binding site of BDMC in the hydrophobic alkyl chains of the mixed micelles was analyzed by copper ion fluorescence quenching analysis, fluorescence polarization analysis, 1H nuclear magnetic resonance spectroscopy, and time-resolved fluorescence spectroscopy. The solubility of BDMC in the mixed micelles was enhanced and SDDS + Tween 60 had more significant solubilization capacity. Therefore, the mixed micellar systems may provide a feasible solution for the application of BDMC in functional food and medicine fields.