The effect of carbomer 934P and different vegetable oils on physical stability, mechanical and rheological properties of emulsion-based systems containing propolis

Semi-solid emulsion systems constitute important platforms for drug delivery, due to the easiness of administration, increasing residence time and also improve the drug availability. They are usually stabilized by emulsifiers and hydrophilic polymers may be used to form a tridimensional network in the hydrophilic phase resulting in a structure than can disperse the hydrophobic phase and the drug. These systems can be administered by oral, parenteral, and topical routes as platforms for delivery of biologically active agents from different origins such as mineral, animal or vegetal. Propolis has a complex chemical composition and displays many important biological activities (antibacterial, fungicidal, antioxidant, antiviral, anti-inflammatory, immunostimulant, anti-cancer, antiulcer, hypotensive and cytostatic). Propolis ethanolic extract (PE) and extract of propolis by-product (BPE) are usually utilized in therapeutics. In this work, three vegetable oils (passion fruit, andiroba and sweet almond oils) were used to develop emulsion-systems composed of Carbopol 934P (C934P) for propolis delivery. The mechanical and rheological properties of formulations were investigated to select potential emulsion systems. A factorial design was employed to determine the influence of C934P concentration and the different vegetable oils on the physicochemical characteristics of systems, considering the presence of PE or BPE. Emulsion systems displayed physicochemical stability and mechanical characteristics dependent of C934P 1% (w/w). Formulations displayed pseudoplastic flow behavior and viscoelasticity dependent of vegetable oil type, temperature and type of propolis extract. The results indicated that the PE resulted in a more structured emulsion system due to the greater content of resin and gum than the BPE. Emulsion systems displayed softness and are worthy of investigation intended the administration on the skin and mucous membranes. (C) 2020 Elsevier B.V. All rights reserved.