Pharmaceutical strategies of improving oral systemic bioavailability of curcumin for clinical application

Curcumin (Cur), a natural compound from Curcuma longa Linn, has various of pharmacological activities such as anti-cancer, anti-inflammatory, anti-oxidant, anti-Alzheimer, anti-microbial and more. Curcumin also has nephroprotective, hepatoprotective, neuroprotective, antirheumatic and cardioprotective effects. However, its low aqueous solubility inhibits the oral bioavailability of curcumin. As well, curcumin can be metabolized rapidly by intestinal tract which can also result in low oral bioavailability. In fact, the bioavailability of curcumin is low even through intraveneous administration routes. Various of pharmaceutical strategies for oral administration including solid dispersions, nano/microparticles, polymeric micelles, nanosuspensions, lipid-based nanocarriers, cyclodextrins, conjugates, polymorphs have been developed in order to improve the oral bioavailability of curcumin. These pharmaceutical strategies can increase the solubility of curcumin, improve the intestinal stability of curcumin, change the absorption route of curcumin and allow for coadministration with other adjuvants. Here we discuss efficacy studies in vitro and in vivo of curcumin nanoformulations, as well as human clinical trials.