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Hydrotropic solubilization--mechanistic studies
1Purdue University, West Lafayette, Indiana 47907, USA.
Pharmaceutical Research
|October 1, 1996
Summary
Hydrotropic solubilization of riboflavin by nicotinamide does not involve complexation. Instead, nicotinamide self-association, which decreases with increasing temperature, is key to its hydrotropic ability.
Area of Science:
- Physical Chemistry
- Pharmaceutical Sciences
Background:
- Hydrotropic solubilization enhances the solubility of poorly soluble compounds.
- The riboflavin-nicotinamide system is a model for studying hydrotropic mechanisms.
- Complexation and self-association are proposed mechanisms for hydrotropic agents.
Purpose of the Study:
- To investigate the mechanism of hydrotropic solubilization using the riboflavin-nicotinamide system.
- To determine if complexation between riboflavin and nicotinamide is the primary mechanism.
- To assess the role of nicotinamide self-association in hydrotropic ability by examining temperature effects.
Main Methods:
- Tested complexation by measuring riboflavin fluorescence quenching and UV/Vis spectral changes upon nicotinamide addition.
- Determined riboflavin solubility in nicotinamide solutions at varying temperatures to evaluate the impact of self-association.
Main Results:
- Nicotinamide did not quench riboflavin fluorescence, and no significant spectral changes indicating complexation were observed.
- Increasing temperature decreased the solubilizing capacity of nicotinamide, indicating temperature dependence of hydrotropic ability.
Conclusions:
- Complexation between riboflavin and nicotinamide is not the mechanism of hydrotropic solubilization.
- The temperature-dependent decrease in nicotinamide's hydrotropic ability suggests that nicotinamide self-association plays a significant role in the mechanism.