Propolis is a honeybee product known for its antioxidant, anti-inflammatory, anticancer, and antimicrobial effects. It is rich in bioactive molecules whose content varies depending on the botanical and geographical origin of propolis. These bioactive molecules have been studied individually and as a part of propolis extracts, as they can be used as representative markers for propolis standardization. Here, we compare the pharmacological effects of representative polyphenols and whole propolis extracts. Based on the literature data, polyphenols and extracts act by suppressing similar targets, from pro-inflammatory TNF/NF-κB to the pro-proliferative MAPK/ERK pathway. In addition, they activate similar antioxidant mechanisms of action, like Nrf2-ARE intracellular antioxidant pathway, and they all have antimicrobial activity. These similarities do not imply that we should attribute the action of propolis solely to the most representative compounds. Moreover, its pharmacological effects will depend on the efficacy of these compounds’ extraction. Thus, we also give an overview of different propolis extraction technologies, from traditional to modern ones, which are environmentally friendlier. These technologies belong to an open research area that needs further effective solutions in terms of well-standardized liquid and solid extracts, which would be reliable in their pharmacological effects, environmentally friendly, and sustainable for production.

We compared the chemical composition, antioxidant and antimicrobial activity of two propolis extracts: one obtained with nonaqueous polyethylene glycol, PEG 400 (PgEP), and the other obtained with ethanol (EEP). We analyzed the total phenolic content (TPC) and the concentrations of ten markers of propolis antioxidant activity with HPLC-UV: caffeic acid, p-coumaric acid, trans-ferulic acid, trans-cinnamic acid, kaempferol, apigenin, pinocembrin, chrysin, CAPE, and galangin. Antioxidant activity was tested using DPPH and FRAP assay, and antimicrobial activity was assessed through minimum inhibitory concentrations (MICs) and minimum biofilm eradication concentration (MBEC) determination. Maceration gave the yield of propolis of 25.2 ± 0.08% in EEP, and 21.5 ± 0.24% in PgEP. All ten markers of antioxidant activity were found in both extracts, with all marker concentrations, except kaempferol, higher in EEP. There was no significant difference between the TPC and antioxidant activity of the PgEP and the EEP extract; TPC of PgEP was 16.78 ± 0.23 mg/mL, while EEP had TPC of 15.92 ± 0.78 mg/mL. Both extracts had antimicrobial activity against most investigated pathogens and Staphylococcus aureus, Acinetobacter baumannii, and Escherichia coli biofilms. EEP was more effective against all tested susceptible pathogens, except E. coli, possibly due to higher content of kaempferol in PgEP relative to other polyphenols. Nonaqueous PEG 400 could be used for propolis extraction. It gives extracts with comparable concentrations of antioxidants and has a good antioxidant and antimicrobial activity. It is a safe excipient, convenient for pediatric and veterinary formulations.

The aim of this research was to assess the degree of heavy metal (cadmium, lead and mercury) contamination of wild boars from central Croatia and thereby conduct further tests to connect the contamination to oxidative stress occurrence. The highest cadmium concentration was noticed in the kidneys of older boars, the lead concentration was approximately the same in the liver and kidneys, but it was much higher than the concentration in the muscles, while the highest mercury concentration was measured in the kidneys of all wild boars. The correlation between the malondialdehyde (MDA) and the heavy metal concentrations was higher in tissue samples taken from younger animals (1 to 3 years of age) than in the tissue samples taken from older animals (5 to 6 years of age). In the kidneys of all wild boars there was a statistically significant connection between the MDA and cadmium concentration; in the kidneys of younger wild boars there was a statistically significant connection between the MDA and lead concentration. Further research on this topic should focus on MDA potential to find its use, not only as a contamination biomarker in the area of ecotoxicology, but also in the evaluation of the hygienic acceptability of animal products.