Low-surfactant microemulsion, a smart strategy intended for curcumin oral delivery

This study aimed to develop a low surfactant concentration curcumin-loaded microemulsion (Curc-ME) having a gastrointestinal pH resistance, intended to prospect its oral use for further curcumin release. The effect of excipients on the apparent solubility of curcumin was assessed and a pseudo ternary phase diagram was designed to produce a low-surfactant microemulsion (ME) system. Curcumin was incorporated into the ME (Curc-ME), and the system was further physicochemically and physically characterized. The entrapment efficiency (EE) was determined by UHPLC. The systems’ stability under storage, and its stability and curcumin release in simulated gastrointestinal fluids (SGIF) were evaluated. The excipients of the ME improved curcumin’s apparent solubility. Curc-ME, stabilized with 15% of surfactants, displayed spherical droplets (sized of 21.81 ± 0.20 nm), polydispersity index of 0.07 ± 0.01, viscosity of 5.33 × 10−3 ± 0.01 Pa.s, conductivity of 160 ± 3 μS cm−1, surface tension of 40.37 ± 0.48 dynes/cm and EE of 98 ± 0.73%. Thermal analyses confirmed curcumin entrapment in the core of the system. The system remained stable over 90 days under storage and under SGIF conditions. Curc-ME revealed a modified and complex kinetics release of curcumin in the SGIF. Overall, the results demonstrate that Curc-ME increased the solubility of curcumin, was produced with a remarkable low surfactant concentration, and showed stability and modified curcumin release at the gastrointestinal tract pHs. Therefore, Curc-ME revealed to be a promising candidate to be further explored as a therapeutic agent.