Hydroxypropyl methycellulose-galactomannan binary complexes achieving 55 wt% curcumin loading capacity: Mechanism and in vitro bioactivity

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Curcumin is a turmeric-derived bioactive flavonoid that is beneficial to human health. Unfortunately, poor water solubility and low bioactivity of curcumin limit its applications. Multiple food-derived curcumin delivery systems have been developed, but their loading capacities still need to be improved. In this work, binary complexes of hydroxypropyl methycellulose-galactomannan (HPMC-GM) with different mannose to galactose (M:G) ratios in GM were manufactured for curcumin delivery. HPMC-GM achieved 40–55 wt% curcumin loading capacity depending on the M:G ratio, which was about twice that of other reported food-derived vehicles. Porous dense networks were observed in HPMC-GM, which were driven by hydrogen bonds and hydrophobic interactions. Curcumin bound tightly to hydrophobic cavities in the amorphous state via hydrophobic interactions and hydrogen bonds. The hydrophilic galactose branches of GM restrict complexation between HPMC and GM. Higher M:G ratios resulted in higher curcumin loading capacities of HPMC-GM. The results of in vitro dissolution and anti-proliferation activity showed that the bioactivity of curcumin loaded in HPMC-GM was superior to unloaded curcumin. This study created delivery systems with high curcumin loading capacities using 100% food-grade materials as vehicles, which circumvents the drawback of using artificial synthetic polymers to achieve high curcumin loading capacity. The HPMC-GM vehicle has great potential in developing curcumin products as dietary supplements as well as for medical purposes.