Department of Food Science, University of Massachusetts-Amherst , Amherst, Massachusetts 01003, United States.
Department of Biochemistry, Faculty of Science, King Abdulaziz University , P.O. Box 80203, Jeddah 21589, Saudi Arabia.
J Agric Food Chem. 2017 Mar 1;65(8):1525-1532. doi: 10.1021/acs.jafc.6b04815. Epub 2017 Feb 16.
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.
姜黄素作为一种营养保健品在食品和补充剂产品中的应用常常受到限制，这是因为它的水溶性低、化学稳定性差、口服生物利用度低。本研究考察了 pH 值、储存温度和分子环境对纯姜黄素在水溶液和油包水乳液中的物理和化学稳定性的影响。与天然存在的姜黄素类混合物（含有姜黄素、脱甲氧基姜黄素和双脱甲氧基姜黄素）不同，纯姜黄素在碱性水溶液（pH≥7.0）中极易发生化学降解，而且在酸性水溶液（pH<7）中容易结晶析出。这些影响归因于不同 pH 条件下姜黄素分子结构的变化。形成的姜黄素晶体相对较大（10-50μm），容易快速沉降。将姜黄素掺入油包水乳液（30% MCT，1mg 姜黄素/g MCT，d≈298nm）可提高其在水中的分散性和化学稳定性。在 37°C 孵育 1 个月后，在酸性条件（pH<7）下储存的乳液中保留了超过 85%的姜黄素，而在 pH 7.0、7.4 和 8.0 下储存的乳液中分别保留了 62%、60%和 53%的姜黄素。在酸性条件下储存时，载有姜黄素的乳液颜色几乎没有变化，但在碱性条件下储存时，其黄色会褪去。在环境温度下储存 31 天，乳液中没有观察到液滴聚集或分层的现象。这些结果表明，基于乳液的递送系统可能适合提高姜黄素的水分散性和化学稳定性，从而促进其在食品和补充剂中的应用。
