Formulation and characterization of Lyophilizated aqueous extracts of propolis

Abstract

Introduction. Freeze – drying, also known as lyophilization, is a method, in which water from frozen materials is removing by sublimation of ice crystals (primary drying) and desorbtion (secondary drying) [1,2]. Advantages of lyophilization: rapid reconstitution time, long preservation period owing to 95%-99.5% water removal, minimal changes in the properties because microbe growth and enzyme effect can not be exerted under low temperature, etc [2]. Freeze drying can be used in the formulation of aqueous extracts of poorly soluble in water substances. For this property, propolis was choosen to make its aqueous extract, instead usual ethanolic. The aim of the study. To formulate lyophilizated aqueous extracts of propolis powder and characterize formulation quality: powder loss of drying, angle of repose, flow, tap density. Materials and methods. Four formulations of 10% aqueous extracts of propolis with 10% bulking agents (Dsorbitol, D-mannitol, sucrose and D(+)-glucose anhydrous) were developed. The extracts were frozen at -80°C in freezer and lyophilized in a lyophilizator under 0,5-0,1 mm-Hg pressure at -50 °C. The quantitative composition of lyophilized powder was investigated with HPLC. Loss of drying was measured by electronic moisture analyzer KERN MLS, angle of repose and flow was measured by flow tester ERWEKA AG, tap density – by tap density tester TD1. A ratio of released and adsorbed heat of developed formulations was determined by microcalorimetry. Mean values and standard deviations of the results were calculated using Microsoft Office Excel 2007 software. Results. The highest amount of fenolic acids and the most appropriate loss of drying was detected in lyophilizated powders with mannitol – respectively 15,28 μg/ml and 0,81%. Excellent flow – 12,5 g/s, angle of repose – 26,5° and tap density – 524,5 kg/m3 was observed of powder with sorbitol. Formulation with mannitol as bulking agent