Citrus sinensis essential oil-based microemulsions: green synthesis, characterization, and antibacterial and larvicide activities

Abstract

The aim of this study was the development and characterization of a new microemulsion composed of sweet orange (Citrus sinensis L.) essential oils (EOCs) and evaluate its antibacterial and larvicide profiles. The optimal combination of EOCs, surfactant (Kolliphor EL), and water was achieved using a ternary phase diagram. EOCs were obtained from orange peel by steam-distillation and analyzed by gas chromatographmass spectrometer (GC-MS). A total of 25 compounds were identified, among which 90 wt % was d-limonene. In order to determine antimicrobial activity of the formulation, minimum inhibitory concentration (MIC) assay was done. d-Limonene, limonene 1,2-epoxide, and -mircene showed a high antibacterial activity. Cell viability studies were performed in L929 murine fibroblast as a cellular line, using the MTT assay. A cell viability of 118% for EOCs and 117.7% for microemulsion after 72 h was recorded indicating no relevant cytotoxic effect. In vivo studies, based on a wax moth, Galleria mellonella (G. mellonella), larvae as a model system showed 100% of larvae mortality under the influence of the microemulsion with EOCs, while a second efficiency rating of 45% for larvae mortality was reached for pure EOCs. These tests confirm a strong larvicide activity for the essential oil, characterized by the highest concentration of limonene as the larvicide agent. The loading of EOCs into microemulsions offered an improved approach for the delivery of this oil which retained its bioactivity, as shown in vitro and in vivo.