Recent advances to improve curcumin oral bioavailability

It has widely been agreed that the oral delivery of curcumin, a highly acknowledged health-promoting bioactive compound, is limited mostly due to its low water solubility, low bioaccessibility, and fast degradation throughout the gastrointestinal tract. However, curcumin oral bioavailability may be boosted via a new generation of delivery systems, resulting in the most recent advances in this field. This review summarizes the recent advances in the five key points that restrict curcumin overall bioavailability; bioaccessibility, absorption, transformation, distribution, and excretion. Emphasis is given to the approaches that eliminate the transformation of curcumin; whereas, the advances in the mucoadhesive delivery systems of this bioactive have been highlighted. The interactions between curcumin and gastrointestinal constituents, the epithelium cells enhancers, and efflux inhibitors have also been reviewed. Promoting curcumin towards its transport to the systemic circulation through the lymphatic system, and not the portal vein, inhibits the metabolic transformation of curcumin. This can be achieved by the curcumin-lipid conjugate approach. An appropriate mucoadhesive delivery system can be used to achieve prolonged curcumin delivery. Loading curcumin in the oil phase and decreasing its presence at the oil-water interface, can significantly avoid its chemical transformation. The solubility of curcumin in oil should be increased up to an optimum concentration, where its health benefits can be achieved without affecting its solubility in gastrointestinal fluid. The size of the oil droplets and the characteristics of their interface, the interactions between curcumin and biopolymer(s) present in the delivery system, and the gastrointestinal tract can also change curcumin bioavailability.