Technological Evaluation of Emulsions Containing The Volatile Oil from Leaves of Plectranthus Amboinicus Lour

BACKGROUND: Plectranthus amboinicus Lour is a species which is widespread throughout tropical countries where it is widely used against respiratory tract disorders such as bronchodilator, antitussive, and expectorant conditions. OBJECTIVE: This study aims to characterize the essential oil of P. amboinicus (PaEO) and produce and evaluate emulsions containing PaEO. MATERIALS AND METHODS: The essential oil was characterized by physical-chemical analyses for density, refractive index, 90% ethanol solubility, color, appearance, and identification by gas chromatography coupled to mass spectrometry detection. The emulsions were prepared following a hydrophile-lipophile balance [HLB] spreadsheet design from two nonionic surfactants (Span 80(®) and Tween 20(®)) producing HLB values ranging from 4.3 to 16.7. The products were stored at room temperature at 5°C. The emulsion stabilities were tested both in the long and short-term. RESULTS: The PaEO was obtained by steam distillation and the total extraction was reached after 3 hours yielding of 0.2% (w/w). This essential oil was characterized by physicochemical analyses for density [1.5 g.ml(-1)], refraction index [0.9167], ethanol 90% solubility [1:2], color, and appearance (yellow/clear). Nineteen components were identified in the oil, among them the sesquiterpenes: carvacrol [33.50%], p-cymene [28.20%] and γ-terpinene [14.77%]. The emulsions obtained successfully showed, for the first time, HLB values for essential oils from Plectranthus amboinicus [15.7]. CONCLUSION: The experimental data shows a relationship between HLB values of the surfactant mixtures contributing to the emulsified systems production containing phytopharmaceuticals. Such an approach is of great importance to the development of lipid carriers for therapeutic drugs. SUMMARY: The essential oil from leaves of Plectranthus amboinicus was extracted by steam distillation and characterized. The emulsions containing essential oil were produced and the stability was performed in the short and long term. The critical hydrophilic-lipophilic balance (HLB) of the essential oil was 15.7 and was achieved by the combination of surfactants (Tween 80(®) and Span 20(®)). Abbreviations used: PaEO: essential oil of P. amboinicus, HLB: hydrophilic-lipophilic balance, CI: Creaming Index, MET: micro-emultocrit technique