Synergistic Antioxidant Activity and Enhanced Stability of Curcumin Encapsulated in Vegetal Oil-Based Microemulsion and Gel Microemulsions

Abstract

Curcumin, due to its antioxidant, antibacterial, anti-inflammatory, and antitumoral activity, has attracted huge attention in applications in many fields such as pharmacy, medicine, nutrition, cosmetics, and biotechnology. The stability of curcumin-based products and preservation of antioxidant properties are still challenges in practical applications. Stability and antioxidant properties were studied for curcumin encapsulated in O/W microemulsion systems and three related gel microemulsions. Only biodegradable and biocompatible ingredients were used for carriers: grape seed oil as oily phase, Tween 80, and Plurol^® Diisostearique CG as a surfactant mix, and ethanol as a co-solvent. For the gel microemulsions, water-soluble polymers, namely Carbopol^® 980 NF, chitosan, and sodium hyaluronate were used. The influence of UVC irradiation and heat treatment on the degradation kinetics of curcumin in the formulations was studied. Because of the antioxidant character of the microemulsion oily phase, the possibility of a synergistic effect between grape seed oil and curcumin was explored. In this study, the high efficiency of the studied drug delivery systems to ensure protection from external degradative factors was confirmed. Also, the influence of the encapsulation in microemulsion and derived gel microemulsion systems on the antioxidant capacity curcumin was studied, and a synergistic effect with vegetal oil was demonstrated.

Keywords: antioxidant activity; curcumin; grape seed oil; microemulsion; synergism.

Figure 1

Visual aspect of microemulsion and gel microemulsion with sodium hyaluronate (see Table 1) with and without encapsulated CURC.

Figure 2

Size and size distribution for void microemulsion (a) and curcumin encapsulating microemulsion (b).

Figure 3

Evolution of the DPPH solution absorbance for CURC encapsulated in various microemulsion systems and reference solvent mixtures (sample denoted in Table 1).

Figure 4

IC₅₀ values of CURC encapsulated in microemulsion, gel microemulsions systems, and reference solvent mixtures (sample denoted in Table 1). (*) statisticaly significant (p < 0.05).

Figure 5

Reduced amount of DPPH, for CURC encapsulated in various microemulsion systems (at 1% concentration) and reference solvent mixtures (sample denoted in Table 1) determined at equilibrium (time = 900 s). (*) statisticaly significant (p < 0.05).

Figure 6

Variation of the % ESC for individual components Grape seed oil (a) and for curcumin (b) at various concentrations equivalent to concentrations at the selected grape seed oil-curcumin mixtures investigated for synergistic effect, at different ratio (v/v): C1 corresponds to 10:1 (v/v) ratio; C2 corresponds to 4.5:10 (v/v) ratio; C3 corresponds to 1:1 (v/v) ratio; C4 corresponds to 1:5 (v/v) ratio; C5 corresponds to 1:10 (v/v) ratio.

Figure 7

Variation of experimental scavenging activity toward DPPH with antioxidant concentration (solid lines represent the best fit of Equation (5) to experimental data).