Development and characterization of monoterpene loaded microemulsions as novel scolicidal agents

Cystic echinococcosis (CE) is one of the most important zoonotic diseases. The primary treatment is surgery and chemical sterilization of the parasitic layers by injection of a scolicidal agent. Available scolicidals possess side effects, and may cause postoperative complications. Several studies reported the scolicidal properties of monoterpene phenols and alcohols such as carvacrol, thymol, and geraniol. The present study aimed to develop, characterize, and assess monoterpene loaded microemulsions as novel green scolicidals products. For this purpose, microemulsions composing 0.37%, 0.75%, and 1.5% of monoterpenoid(s), thymol, carvacrol, and geraniol, alone or in binary or ternary mixtures were formulated. Samples were analyzed by visual inspection, polarizing optical microscope, and dynamic light scattering (DLS). The stability of the samples was evaluated up to a 3-month storage. For the scolicidal bioassay, samples at different concentrations of 200, 100, 50, 25, and 10 μg/ml were added to wells containing 10⁴ viable protoscoleces and mortality rates were recorded at 2, 5, 10, and 20 min after exposure. Results of the present study showed that microemulsions formulated with 0.75% of pure carvacrol or the binary mixture of thymol and carvacrol at 0.375% are promising scolicidal agents.