29 research outputs found
Physical and Chemical Stability of Curcumin in Aqueous Solutions and Emulsions: Impact of pH, Temperature, and Molecular Environment
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, <i>d</i><sub>32</sub> ≈ 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