The Protective effect of aqueous and non-aqueous propolis extracts in primary rat brain cell culture against hypoxia

Abstract

Introduction: Propolis is one of the most fascinating honey bee (Apis mellifera L.) products. The constituents of propolis are flavonoids, phenolic acids, terpenes, aromatic acids and others, most of them are soluble in ethanol and that is why propolis is commonly used as ethanolic extract. Water-based propolis extracts are more biocompatible and could be applied more safely but they have significantly smaller range and quantity of active substances (1). Propolis is known to have antioxidative, anti-inflammatory, antimicrobial, immunomodulatory, neuroprotective and other effects (2). The aim of this study is to determine the effect of different propolis extracts to the primary rat brain cell culture after 24 hours hypoxia. Materials and methods: Crude propolis was grounded into powder and macerated in different solvents (water, 20% polyethylenglycol/water and 70% ethanol) by shaking. Extraction time - 5 hours in room temperature. Propolis sample-to-solvent ratio was 1:10 (w/v). After extraction, extracts of propolis were filtered through paper filter and stored at 4 °C (1). The primary rat brain cell culture was incubated for 24 hours in hypoxic conditions. The vitality of cell culture was measured using Propidium Iodide/Hoechst method. Results: After 24 hours of hypoxia, control group had 21,7% necrotic cells and 1,2% apoptotic cells. Different concentrations of ethanolic extracts and the lowest concentrations of aqueous extracts (3 μg/ml of phenolic compounds (PC) and 6 μg/ml PC) had no protective effect. The tendency to protect cells against hypoxia was seen when the concentration of aqueous extracts was higher (12 μg/ml PC; 18 μg/ml PC) – count of necrotic cells was 9,7% and 7,7%, apoptotic cells - 1,8% and 1,1%. The highest protective effect was achieved using 5 μg/ml PC – 32 μg/ml PC concentration aqueous-polyethylenglycolic extracts (necrotic cells – 2,4-11,85%, apoptotic cells – 0,6-1,65%). Conclusions: Aqueous and aqueous-polyethyleng