Preparation, characterization and photostability assessment of curcumin microencapsulated within methacrylic copolymers

Microencapsulated curcumin (CUR) was obtained by coevaporation with polymethacrylate polymers (blends at various percent ratios of Eudragit® RS100 and RL100 resins). The suspensions were freeze-dried to produce free flowing microparticles, which were sieved in the 420-90 μm range. They were characterized in the solid state for micromeritic properties and drug loading, and by FT-IR, powder X-ray diffractometry and differential scanning calorimetry for physical state. Encapsulation efficiency largely varied from 35 to 95%, mainly depending on the copolymer composition and to a less extent from drug-to-polymer ratio. Solid-state characterization confirmed the chemical stability of CUR in microparticles, and suggested that the drug was in a microcrystalline form within the polymer matrix; microscopy analysis confirmed the latter statement. In vitro release and dissolution profile of neat and encapsulated CUR were assessed in simulated gastric and intestinal fluids: from these studies, it was however found that the microencapsulation of CUR in these polymers did not improve the solubility of this very poorly soluble compound in simulated gastric and intestinal aqueous media. Interestingly, photostability experiments showed that the dispersion of CUR in the polymer matrix effectively protects the drug from light-induced chemical degradation, with an effect dependent on the drug-to-polymer ratio