HLB value, an important parameter for the development of essential oil phytopharmaceuticals

Abstract

Essential oils are used primarily as natural preservatives, fl avourants and fragrances in cosmetic products. Several pharmacopeias possess monographs of plants which are good sources of essential oils, such as Brazilian Pharmacopeia, including Illicium verum Hook. f., Schisandraceae and Rosmarinus officinalis. Since determination of Hydrophile-Lipophile Balance (HLB) value of essential oils appears as a critical step for development of emulsions and other semi-solid formulations, evaluation of required HLB values for I. verum and R. officinalis essential oils is the aim of this study. They were obtained by hydrodistillation and several emulsions were prepared by changing emulsifiers. The couple sorbitan oleate/polysorbate 20 provided best emulsions and was used at different ratios, at a total blend concentration of 5% w/w. The lowest mean droplet diameters for R. officinalis and I. verum emulsions were obtained at HLB 16.5 (97.12 nm) and 16.7 (246.6 nm), respectively. Moreover, emulsions with R. officinlis were finer and presented some bluish reflection, characteristic of nanoemulsions. The lowest turbidity value for R. officinalis emulsion was also obtained at HLB 16.5 (0.33). Thus, the present study describes for the first time HLB values for R. officinalis (16.5) and I. verum (16.7) essential oils, contributing to their physicochemical characterization and technology development of phytopharmaceuticals.