Modelling and biopharmaceutical evaluation of microemulsions containing propolis phenolic compounds

V. Greičiūnaitė‘s final thesis for masters’s degree ,,Modelling and biopharmaceutical evaluation of microemulsions containing propolis phenolic compounds‘‘/ scientific supervisor lect. dr. Modestas Žilius; Lithuanian University of Health Sciences, Faculty of Pharmacy, department of Clinical Pharmacy. – Kaunas. The aim of work: to formulate oil-in-water type microemulsions and to evaluate propolis phenolic acids (vanillic, caffeic, p-coumaric, ferulic acids) and vanillin release in vitro from modelled microemulsions. Main tasks: to evaluate solubility of propolis phenolic coumpounds in the components of microemulsions; to formulate oil-in-water type microemulsions and to evaluate thermodynamic stability and physicochemical properties of microemulsions; to optimize the composition of selected microemulsions; to evaluate physicochemical properties of microemulsions containing propolis phenolic compounds; to evaluate the release of propolis phenolic acids and vanillin from the optimal composition of microemulsions. Methods: identification and quantification of propolis phenolic compounds was performed by validated HPLC method. The particles sizes and values of polydispersity indexes of microemulsions were determined by dynamic light scattering method. Biopharmaceutical in vitro release studies were performed by modified Franz type diffusions cells system. Results: the average particle size of oil-in-water type optimal composition microemulsions containing propolis phenolic compounds was from 171.3 nm to 311.6 nm. The polydispersity index was in the range of 0.077–0.178, pH varies from 4.5 to 5.3, the viscosity was in the range of 48.9–59.2 mPa·s, the conductivity was in the range of 13.2–23.3 μS/cm. After 4 hours the highest amount of released propolis phenolic compounds were 5.28 ± 0.51% and the flux was 75.58 ± 7.23 μg/cm2 from oil-in-water type microemulsion containing 7.0% of isopropyl myristate, 31.0% of purified water, 62.0% of the mixture of surfactant and cosurfactant (5:1 ratio). After the selection of suitable composition, oil-in-water type microemulsion, complied with the requirements of the quality, was modelled. This microemulsion containing 1.1% of isopropyl myristate, 36.9% of purified water, 62.0% of the mixture of labrasol and PEG-400 (5:1 ratio). Conslusions: the largest amount of propolis phenolic compounds (p-coumaric, ferulic, vanillic, caffeic acids and vanillin) was extracted using ethanol. Microemulsion containing 1.1% of isopropyl myristate, 36.9% of water, 62.0% of the mixture of labrasol and PEG-400 (5:1 ratio) complied with the requirements of the quality. The most suitable to release the highest amount of propolis phenolic compounds is microemulsion containing 7.0% of isopropyl myristate, 31.0% of water, 62.0% of the mixture of labrasol and PEG-400 (5:1 ratio)