Formulation and characterization of oil-in-water microemulsions for enhanced solubility and stability of curcumin Formulación y caracterización de microemulsiones aceite-en-agua para incrementar la solubilidad y estabilidad de curcumina.

abstract

© 2019 Latin American and Caribbean Consortium of Engineering Institutions. All rights reserved.Curcumin is a natural pigment found in turmeric, a perennial member of the Zingiberaceae family cultivated in southeast Asia, where it has been used since ancient times in natural therapies. Turmeric's rhizome, contains a group of natural pigments called curcuminoids, which make up from 2 - 6% of the stem and are responsible its characteristic yellow - orange coloration. The three pigments contained in turmeric are curcumin, demethoxycurcumin and bisdemethoxycurcumin, with curcumin being the most abundant of the three at 77% of the overall average amount of the curcuminoids present in turmeric. These compounds have demonstrated antioxidant, antiinflamatory and anticarcinogenic properties with potential therapeutic applications, but their low solubility in water and rapid metabolization has limited their incorporation in pharmaceutic and nutraceutic formulations. There are three main alternatives proposed to increase curcumin's solubility in water: its administration with adjuvants or compounds that will help increase curcumin's uptake, like piperine or turmeric oil; incorporation in polymeric nanoparticles that can be easily degraded by the body or its incorporation in liquid dispersions where, under the right conditions, preparation costs can be limited only to the dispersion's components. Microemulsions in particular are liquid dispersions with high solubilization potential and are composed of water, oil and a surfactant. They have an average droplet size of 2-50 nm and are thermodynamically stable, meaning they will remain disperse if the remains under the correct conditions. This study contemplates proposing and researching a new pseudoternary system employing an oil and nonionic surfactant already used in nutraceutic or pharmaceutir formulations in order to formulate oil-in-water microemulsions with potential anticarcinogenic activity. The solubility limit of curcumin on those dilution lines was ditermined first, then viscosity and electric conductivity measurements yielded information regarding the compositions where microstructure transitions occur, whereas studying the dispersions' mean droplet size on a set period proved the stability of the system even with curcumin dissolved. Finally, the mixtures were evaluated on their capacity to remain stable on the presence of cell culture medium and their citotoxic activity on a carcinogenic cell line, with the curcumin-loaded microemulsions inhibiting cell growth completely at curcumin concentrations up to 9 ¿g/mL. Summarizing, curcumin-loaded microemulsions were formulated with the ternary system comprised of Water:Butyl (-) lactate:Brij® O10. The pseudoternary system was characterized by studying curcumin's solubility in the microemulsions, their viscosity, electric conductivity, mean droplet size, stability and citotoxic activity on carcinogenic cells in order to incorporate the formulations into future nutraceutic and pharmaceutic therapies that may better harness curcumin's beneficial properties.