The bioactivity of a product can be quantitatively measured and analyzed by assessing its ability to protect, retain normal moisture and delay the aging process of skin. O/W emulsions are commonly used cosmetic delivery systems that supply moisture to skin and improve its condition by forming an occlusive barrier on the skin surface.1 In recent years, scientists have been looking at utilizing natural resources in cosmetic products, as natural vegetal oils are readily available at affordable costs and have excellent cosmetic and skin care application properties such as soothing, moisturizing and skin penetrating. Vegetal oils such as soybean oil, corn oil, safflower oil and linseed oil are used for cosmeceutical purposes as w/o emulsions using single or mixed surfactants.2–4
Prunus dulcis (almond) oil, Carthamus tinctorius (safflower) oil and Passiflora aincarnata (palm) oil share oleic acid as a major fatty acid and are rich in tocopherols and tocotrienols. The added benefits of these oils are moisturizing, emollient and soothing properties that make them an alternative for a topical skin treatment. A literature survey revealed that few oils are explored in the form of o/w cosmetic formulation. Reports on rheological properties are scarce, and hence this study was conducted.
Cosmetic emulsions with phosphate-based surfactants derived from the long-chain Guerbet alcohols and a polymeric thickener were characterized by rheological measurements, particle size distribution and stability test.5, 6 Emulsifying agents play a vital role in emulsion stabilization, either by reducing the interfacial tension of the system and/or by forming an interfacial film with electrostatic properties around the dispersed globules. The proper concentration of surfactants and their mixtures give synergistic effect with respect to the stability of the emulsion by the proper matching of hydrophilic-lipophilic balance (HLB) numbers of dispersed phase and surfactant used.7