Physical and Chemical Stability of Curcumin in Aqueous Solutions and Emulsions: Impact of pH, Temperature, and Molecular Environment

Abstract

The utilization of curcumin as a nutraceutical in food and supplement products is often limited because of its low water solubility, poor chemical stability, and low oral bioavailability. This study examined the impact of pH, storage temperature, and molecular environment on the physical and chemical stability of pure curcumin in aqueous solutions and in oil-in-water emulsions. Unlike naturally occurring curcuminoid mixtures (that contain curcumin, demethoxy-curcumin, and bisdemethoxy-curcumin), pure curcumin was highly unstable to chemical degradation in alkaline aqueous solutions (pH ≥7.0) and tended to crystallize out of aqueous acidic solutions (pH <7). These effects were attributed to changes in the molecular structure of curcumin under different pH conditions. The curcumin crystals formed were relatively large (10-50 μm), which made them prone to rapid sedimentation. The incorporation of curcumin into oil-in-water emulsions (30% MCT, 1 mg curcumin/g MCT, d ≈ 298 nm) improved its water dispersibility and chemical stability. After incubation at 37 °C for 1 month, >85% of curcumin was retained by emulsions stored under acidic conditions (pH <7), whereas 62, 60, and 53% was retained by emulsions stored at pH 7.0, 7.4, and 8.0, respectively. There was little change in the color of curcumin-loaded emulsions when stored under acidic conditions, but their yellow color faded when stored under alkaline conditions. There was no evidence of droplet aggregation or creaming in emulsions stored for 31 days at ambient temperature. These results suggest that emulsion-based delivery systems may be suitable for improving the water dispersibility and chemical stability of curcumin, which would facilitate its application in foods and supplements.

Characteristics of Curcumin-Loaded Bacterial Cellulose Films and Anticancer Properties against Malignant Melanoma Skin Cancer Cells

“…Therefore, the concentrations of curcumin released from BCC films into the acetate buffer were higher than those in the PBS buffer. Degradation should occur very slowly at pH 1-6, whereas degradation could occur at a significantly higher rate in PBS at pH 7.4 due to the instability of curcumin at this pH [18,39]. This degradation could cause the decrease in the concentration of curcumin in the solution that was seen in the release assay after 10 h. This result demonstrates that BC is a good candidate matrix for the controlled release of curcumin.…”

Recent Updates in Curcumin Pyrazole and Isoxazole Derivatives: Synthesis and Biological Application

“…Pyrazole curcumin, synthesized by using microwave, was found to be more potent inhibitor of CaMKII than curcumin. Molecular docking revealed that hydroxy, carbonyl and pyrazole ring of curcumin, pyrazole and isoxazole derivatives form hydrogen bonds with the protein residues (Table 14). Thus, acute inhibition of CaMKII may be a potential strategy for providing neuroprotection as shown by two independent groups using the CaMKII inhibitor tat-CN21 peptide.…”

Molluscicidal and cercaricidal activities of curcumin on Biomphalaria glabrata and Schistosoma mansoni cercariae

“…As expected for hydrophobic compounds, CUR has poor solubility in water at ambient pressure and temperature conditions, and its log P value is between 2.5 and 3.6 . Furthermore, it is soluble in polar organic solvents, such as DMSO . Other molluscicidals, such as niclosamide, are recommended by the WHO for snail control and are also poorly soluble in water …”