Abstract
The influence of heating at a temperature of 50 °C and UV-irradiation of propolis drops and spray on their free radical scavenging activity was determined. The kinetics of interactions of the propolis samples with DPPH free radicals was analyzed. Interactions of propolis drops and propolis spray with free radicals were examined by electron paramagnetic resonance spectroscopy. A spectrometer generating microwaves of 9.3 GHz frequency was used. The EPR spectra of the model DPPH free radicals were compared with the EPR spectra of DPPH in contact with the tested propolis samples. The antioxidative activity of propolis drops and propolis spray decreased after heating at the temperature of 50 °C. A UV-irradiated sample of propolis drops more weakly scavenged free radicals than an untreated sample. The antioxidative activity of propolis spray increased after UV-irradiation. The sample of propolis drops heated at the temperature of 50 °C quenched free radicals faster than the unheated sample. UV-irradiation weakly changed the kinetics of propolis drops or spray interactions with free radicals. EPR analysis indicated that propolis drops and spray should not be stored at a temperature of 50 °C. Propolis drops should not be exposed to UV-irradiation.
Highlights
Propolis is a well-known, complex, resinous, natural material collected by honeybees (Apis mellifera L.) from various plant sources such as leaves, buds, barks and exudates [1,2,3]
Electron paramagnetic resonance spectroscopic studies of the electron paramagnetic resonance (EPR) spectra of model DPPH free radicals illustrated the antioxidative character of both propolis drops and propolis spray
The propolis samples interacted with DPPH free radicals and they quenched DPPH EPR lines as the result of the free radical scavenging activity
Summary
Propolis (bee glue) is a well-known, complex, resinous, natural material collected by honeybees (Apis mellifera L.) from various plant sources such as leaves, buds, barks and exudates [1,2,3]. This natural mixture exhibits a wide variety of botanical sources and chemical compositions, depending on the bee species, location of the production and the collection season [4,5,6]. Poplar propolis, used in the present study, contains 50% of resins and vegetable balms, 30% of wax, 10% of aromatic and essential oils, 5% of pollen, and 5% of additional active substances [10]. The most important of them are the following compounds: phenolic acids (benzoic, cinnamic, caffeic and ferulic acids), phenols
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