Abstract
BackgroundPropolis is multicomponent substance collected by honeybees from various plants. It is known for numerous biological effects and is commonly used as ethanolic extract because most of active substances of propolis are ethanol-soluble. However, water-based propolis extracts could be applied more safely, as this solvent is more biocompatible. On the other hand, water extracts has significantly smaller range and quantity of active compounds. The extraction power of water could be enhanced by adding co-solvent which increases both solubility and penetration of propolis compounds. However, variation of solvents results in different composition of active substances that might have distinct effects. The majority of biological effects of propolis are attributed to the antioxidant properties of its active compounds. Antioxidant effect might be a result of either direct scavenging of ROS or modulation of ROS producing organelle activity. Therefore, the aim of this study was to investigate and compare chemical composition, antioxidant properties and effects on mitochondrial respiration of aqueous (AqEP), polyethylene glycol-aqueous (Pg-AqEP) and ethanolic (EEP) propolis extracts.MethodsChemical composition of propolis extracts was determined using HPLC and Folin-Ciocalteu method. Ability to neutralize H2O2 and intracellular ROS concentration in C6 glioma cells were determined fluorometrically by using 10-acetyl-3,7-dihydroxyphenoxazine and 2′,7′-dichlorofluorescein diacetate, respectively. Mitochondrial superoxide generation was assessed under fluorescent microscope by using MitoSOX Red. Oxygen uptake rates of mitochondria were recorded by high-resolution respirometer Oxygraph-2 k.ResultsOur data revealed that phenolic acids and aldehydes make up 40–42% of all extracted and identified compounds in AqEP and Pg-AqEP and only 16% in EEP. All preparations revealed similar antioxidant activity in cell culture medium but Pg-AqEP and EEP demonstrated better mitochondrial superoxide and total intracellular ROS decreasing properties. At higher concentrations, AqEP and EEP inhibited mitochondrial respiration, but Pg-AqEP had concentration-dependent mitochondria-uncoupling effect.ConclusionsAqueous and non-aqueous propolis extracts differ by composition, but all of them possess antioxidant properties and neutralize H2O2 in solution at similar efficiency. However, both Pg-AqEP and EEP were more effective in decreasing intracellular and intramitochondrial ROS compared to AqEP. At higher concentrations, these preparations affect mitochondrial functions and change energy production in C6 cells.
Highlights
Propolis is multicomponent substance collected by honeybees from various plants
Aqueous and non-aqueous propolis extracts differ by composition, but all of them possess antioxidant properties and neutralize H2O2 in solution at similar efficiency
Both Polyethylene glycol (Pg)-Aqueous extract of propolis (AqEP) and ethanolic extract of propolis (EEP) were more effective in decreasing intracellular and intramitochondrial reactive oxygen species (ROS) compared to AqEP
Summary
Propolis is multicomponent substance collected by honeybees from various plants It is known for numerous biological effects and is commonly used as ethanolic extract because most of active substances of propolis are ethanol-soluble. Variation of solvents results in different composition of active substances that might have distinct effects. The majority of biological effects of propolis are attributed to the antioxidant properties of its active compounds. Numerous combinations of chemical compounds and concentrations of propolis examples result in a large and diverse biological activity [3]. For these properties, propolis was well-known in folk medicine and effectively used for treatment of various human diseases [4]. The amount of research done on propolis during last decades demonstrates a vast spectrum of its’ biological activity, such as antiseptic, anti-inflammatory, antioxidant, antibacterial, antifungal, antineoplastic, hepatoprotective, cardioprotective and immunomodulatory [5, 6]
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