Formulation of anti-larval nanoemulsion: Impact of droplet size on larvicidal activity against malaria vectors in Chhattisgarh, India

Abstract

Mentha piperita (peppermint) essential oil nanoemulsion was prepared by low energy spontaneous emulsification method. GC-MS analysis revealed the composition of peppermint essential oil and menthol (45.2%) was the major bioactive compound along with menthone (15.39%), neomethol (8.1%), menthyl acetate (7.7%) and isomenthone (7.4%). Optimization of the nanoemulsion preparation process was done by Response Surface Methodology (RSM) with Central Composite Design (CCD). The droplet diameter and polydispersity index at optimized conditions (15% oil concentration, 25% surfactant concentration and Tween80 as surfactant) were 39.2 nm and 0.22 respectively. Optimized peppermint oil nanoemulsion (OPNE) was optically transparent, spherical in morphology and was stable for 6 months. OPNE formulation demonstrated dose, time and size-dependent larvicidal activity against malaria vectors with LC50 value of 48 ppm and 123 ppm against Anopheles culicifacies and Anopheles stephensi respectively. The LC50 values were 90 ppm and 163 ppm against Anopheles culicifacies and Anopheles stephensi correspondingly for the bigger droplet size formulation (PNE, droplet diameter: 129.6 nm) confirming the droplet size-dependent larvicidal activity of the nanoemulsion. The results of this study propose that peppermint oil-based nanoemulsion possibly be used as an eco-friendly larvicide for mosquito vector control strategies.