Physicochemical and antimicrobial properties of soaps formulated with essential oils of some plant species

Abstract

In recent decades, there has been a growing global interest in natural and sustainable alternatives to synthetic chemical products, particularly in the area of personal hygiene. Conventional soaps often contain synthetic chemicals such as triclosan and parabens, which have been linked to antimicrobial resistance and skin irritation. Essential oils with diverse antimicrobial properties offer a promising alternative for enhancing soap formulations. This study was conducted to evaluate the physicochemical properties and antimicrobial properties of soap formulated with essential oils extracted from plant species. Essential oils from Hyptis suaveolens, Citrus aurantifolia, Curcuma longa, Citrus limon, and Thuja koraiensis were obtained through the hydrodistillation method using a Clavenger apparatus. Soap was prepared using the hot process method and was fortified with essential oils using the standard method. The physicochemical properties of the essential oil (pH, viscosity, specific gravity, and color) were analyzed. The soaps were evaluated for detergency, foaming capacity, and antimicrobial activity against some selected bacterial and fungal isolates. The results showed that the essential oils showed acceptable pH, viscosity, specific gravity, and good lathering properties comparable to conventional soaps. The antimicrobial assays demonstrated that soaps containing essential oils displayed enhanced inhibitory effects compared to the plain soap, with formulated soaps showing the broadest antimicrobial spectrum. The essential oils also demonstrated strong concentration-dependent activity against both bacteria and fungi. These confirm the synergistic antimicrobial effect of the unformulated soap, formulated soap, and essential oils, highlighting their potential for producing safe, effective, and affordable hygiene products. The study concludes that the essential oils and the formulated soaps offer enhanced cleansing, dermatological safety, and antimicrobial effectiveness, making it a promising natural alternative to synthetic soaps.