There is no systematic report about propolis chemical biodiversity from the Adriatic Sea islands affecting its antioxidant capacity. Therefore, the samples from the islands Krk, Rab, Pag, Biševo and Korčula were collected. Comprehensive methods were used to unlock their chemical biodiversity: headspace solid-phase microextraction (HS-SPME) and hydrodistillation (HD) followed by gas chromatography and mass spectrometry (GC-MS); Fourier transform mid-infrared spectroscopy (FT-MIR); ultra high performance liquid chromatography with diode array detector and quadrupole time-of-flight mass spectrometry (UHPLC-DAD-QqTOF-MS) and DPPH and FRAP assay. The volatiles variability enabled differentiation of the samples in 2 groups of Mediterranean propolis: non-poplar type (dominated by α-pinene) and polar type (characterized by cadinane type sesquiterpenes). Spectral variations (FT-MIR) associated with phenolics and other balsam-related components were significant among the samples. The UHPLC profiles allowed to track compounds related to the different botanical sources such as poplar (pinobanksin esters, esters and glycerides of phenolic acids, including prenyl derivatives), coniferous trees (labdane, abietane diterpenes) and Cistus spp. (clerodane and labdane diterpenes, methylated myricetin derivatives). The antioxidant potential determined by DPPH ranged 2.6–81.6 mg GAE/g and in FRAP assay 0.1–0.8 mmol Fe²⁺/g. The highest activity was observed for the samples of Populus spp. origin. The antioxidant potential and phenolic/flavonoid content was positively, significantly correlated.

The major developments and concepts in the study of terpenes (mainly monoterpenes) as well as C₉-, C₁₀-, C₁₃-, C₁₄- and C₁₅- norisoprenoids in honey are summarized. Their occurrence and biosynthetic correlations (terpene transformations, particularly the generation of linalool derivatives as well as carotenoid degradation and the corresponding variety of norisoprenoids) are discussed considering the plant/nectar/bee-stomach composition and hive conditions (e.g. warm and acidic conditions that can lead to oxidative degradation of compounds). Terpenes up to C₁₅ have been found as major compounds of the essential oils, but honeys from the same plant sources exhibit only partial similarity to the oil composition (e.g. lavender, sage or citrus essential oils/honeys). The formation of heat-derived or prolonged storage artefacts in honey (mainly the products of Maillard reactions and Strecker degradation reactions) influence the honey composition, and hotrienol is particularly labile among the chemical groups discussed. Stimulated by the challenges of fingerprinting methods and structure identification, exploratory studies (including our published results) on terpenes and norisoprenoids are summarized with emphasis on identifying specific or nonspecific chemical markers of the botanical origin of honey. In general, nonspecific biomarkers dominate in different honey types (e.g. monoterpenes: linalool, linalool oxide isomers or lilac alcohol/aldehyde isomers; norisoprenoids: isophorone and vomifoliol derivatives) while only a few specific biomarkers are found (e.g. anhydrolinalool oxide isomers, 3,4-dihydro-3-oxoedulan isomers, 3-oxo-retro-α-ionol isomers, kamahine A-C or meliracemoic acid).

The use of honey as an antimicrobial agent gains importance due to often ineffectiveness of conventional treatment. However, activity of honey depends mainly on its botanical and geographical origin. To date, antimicrobial potential of Polish honeys has not yet been entirely investigated. In this study, 37 unifloral samples of 14 honey types (including rare varieties) from Poland were analysed and compared with manuka honey. The most active were cornflower, thyme and buckwheat honeys. Their MICs ranged from 3·12 to 25·00%, (depending on tested micro‐organism) and often were lower than for manuka honey. Additionally, colour, antioxidant activity, total phenols, pH and conductivity were assessed and significant correlations (P < 0·05) of MICs with several parameters were found. The most active were darker honeys, with strong yellow colour component, rich in phenolics, with high conductivity and water content. The honey antibacterial properties depended mainly on peroxide mechanism and were vulnerable to excessive heating, but quite stable during storage in cold. A number of honey samples showed potential as effective antimicrobial agents. The observed correlations of MICs and physical–chemical parameters help to understand better the factors impacting the antibacterial activity. Significance and Impact of the Study Honey is a promising agent in the treatment of non‐healing infected wounds. Thirty‐seven unifloral samples of 14 honey varieties from Poland were analysed for their antimicrobial activity and compared with manuka honey. Several honey types exert even higher antimicrobial potential and could be introduced to wound therapy. Additionally, positive correlations of the antimicrobial activity were found, especially with yellow colour and could be important in the search and screening of the honey active against Escherichia coli.

The antimicrobial activity of 144 samples of honeys including 95 products from apiaries located in Northern Poland was evaluated. The antibacterial activity of those natural products, their thermal stability, and activity in the presence of catalase was investigated by microdilution assays in titration plates. The MTT assay was performed for the determination of anti-biofilm activity. Spectrophotometric assays were used for the determination of antioxidant potential, total phenolic content, and ability to generate hydrogen peroxide. Some of the investigated honeys exhibited surprisingly high antimicrobial, especially anti-staphylococcal, potential, with Minimal Inhibitory Concentration (MIC) values of only 1.56% (v/v). Much higher resistance was observed in the case of staphylococci growing as biofilms. Lower concentrations of the product, up to 12.5% (v/v) stimulated its growth and effective eradication of biofilm required concentration of at least 25% (v/v). Hydrogen peroxide has been identified as a crucial contributor to the antimicrobial activity of honeys supplied by Polish beekeepers. However, some of the results suggest that phytochemicals, especially polyphenols, play an important role depending on botanical source (both positive, e.g., in the case of buckwheat honeys as well as negative, e.g., in the case of some rapeseed honeys) in their antimicrobial potential.