Abstract
Background: The quality and stability of castor oil emulsions may be influenced by the type and amount of its constituent emulsifiers. To our knowledge, the emulsifying potential of single, double, and triple-emulsifier systems comprising of Tween 20, acacia gum and methyl cellulose have never been compared. The aim of the work was to formulate castor oil emulsions stabilized using natural and/or synthetic emulsifying agents and evaluate their organoleptic, physicochemical, and stability profiles. Methods: Six types of emulsions were prepared using the spontaneous emulsification method, and characterised in terms of their physical properties; centrifugation analysis, and real-time stability profile at 25 ℃ and 40 ℃ for 90 days. Results: FT-IR analysis suggested that castor oil was compatible with all the studied emulsifiers. Tween 20-stabilised formulation (F2) and acacia gum/methyl cellulose-based samples (F5) exhibited unacceptable organoleptic attributes and/or physical properties. The physical properties of the remaining castor oil macroemulsions were satisfactory: pH (6.2 to 7.0); electrical conductivity (2253-4557 µS/cm); spreadability (0.7-2.1 cm); oil globule size (2.73-3.74 µm), and creaming index (9-18 %). The emulsions exhibited varying degree of instability over time and with elevated temperatures. The most promising emulsion was acacia gum/methyl cellulose/tween 20-stabilised sample F7: pH: 6.9, electrical conductivity: 4557 µS/cm, spreadability: 1.37 cm, oil globule size: 3.74 µm, creaming index: 9 %, and satisfactory stability profile at 25 °C and 40 °C. Conclusion: Sample F7 may serve as cream base for dermal and transdermal delivery of active pharmaceutical ingredients intended to treat various local skin problems and systemic diseases.
Highlights
IntroductionEmulsions are colloidal dispersions that consist of at least two immiscible phases (oily and aqueous) in which one of the components (dispersed phase) is dispersed in the other system (continuous phase), and stabilized by emulsifiers/surfactants [1]
FT-IR data The typical absorption bands for pure castor oil are presented in Fig. 1a: 723.1 cm-1, 2851 cm-1, 2922.2 cm-1 (C-H stretch of methyl groups), 1162.9 cm-1, 1740.7 cm-1 (C-O-C ester of carbonyl groups), 1457.4 cm-1, 3004.2 cm-1 (C=C alkenyl groups), 3410.5 cm-1 (O-H bend of primary alcohol) while that of tween 20 was detected at 752.9 cm-1, 2873.8 cm-1 (-CH alkyl groups), 1237.5 cm-1 (C-O-C), and 3369.5 cm-1 (-OH stretch)
The current study revealed that castor oil emulsions containing 35 % of castor oil and stabilised using similar amount of acacia gum and methyl cellulose were 2.9 and 3.7 μm, respectively
Summary
Emulsions are colloidal dispersions that consist of at least two immiscible phases (oily and aqueous) in which one of the components (dispersed phase) is dispersed in the other system (continuous phase), and stabilized by emulsifiers/surfactants [1]. There are various parameters that determine the type of emulsion formed: Proportion of oily phase to aqueous phase, with oil-in-water emulsions formulated when the dispersion phase constitutes more than 45 % of the formulation weight and vice-versa; The hydrophile-lipophile balance (HLB) of emulsifying agents, with emulsifiers exhibiting HLB values between 9 and 12 generating oil-in-water emulsions while water-in-oil emulsions are formed when the HLB range of the emulsifier is between 3 and 6 [4]. Emulsions containing photo-labile ingredients are secured in light resistant containers while anti-oxidants and fungistatic preservatives are included in pharmaceutical emulsions to improve their long term stability [2]. The aim of the work was to formulate castor oil emulsions stabilized using natural and/or synthetic emulsifying agents and evaluate their organoleptic, physicochemical, and stability profiles
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