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.

Selenium is a trace element of vital importance for ecosystem functioning and human health mainly due to its antioxidant and protective properties. Since both selenium deficiency and excess can have harmful effects on living organisms, monitoring its distribution in biological systems and the environment is of significant scientific and public health interest. This study systematically assessed selenium concentrations in biological (urine, serum, and hair) and environmental (soil and dandelion) samples in eastern Croatia. Selenium concentrations were determined using the inductively coupled plasma mass spectrometry method. In biological samples, median selenium concentrations were from 15.02 to 37.15 μg·L⁻¹ in urine, from 80.76 to 114.05 μg·L⁻¹ in serum, and from 0.21 to 0.46 µg·g⁻¹ in hair. In environmental samples, median selenium concentrations varied depending on location, ranging from 0.32 to 0.51 mg·kg⁻¹ in soil and from 6.55 to 84.41 µg·kg⁻¹ in dandelion. PCA was applied to identify overall patterns and groupings among biological and environmental samples, showing that dandelion samples from urban locations exhibited the highest selenium concentrations, indicating the influences of urban environmental conditions on selenium accumulation.