Activity of Polish unifloral honeys against pathogenic bacteria and its correlation with colour, phenolic content, antioxidant capacity and other parameters.

UNLABELLED: 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.

Molecular diversity of volatile compounds in rare willow (Salix spp.) honeydew honey: identification of chemical biomarkers.

Salix spp. honeydew honey volatiles were analyzed for the first time by headspace solid-phase microextraction (HS-SPME) and ultrasonic solvent extraction (USE) followed by gas chromatography and mass spectrometry (GC, GC-MS). The use of HS-SPME and USE had advantageous results over the use of one single technique, as it provided different complementary chromatographic profiles for a comprehensive screening of the honeydew volatile composition. The volatiles with different functionality, molecular weight, and polarity were extracted and identified. High percentages of benzoic acid, phenylacetic acid, 2-hydroxybenzoic acid, 4-hydroxyphenylacetic acid with minor percentages of 4-methoxybenzoic acid, 4-hydroxyphenylethanol, and 4-hydroxybenzoic acid from USE extracts can be emphasized as volatile biomarkers of this honeydew that probably originated from Salix spp., as well as methyl salicylate identified only by HS-SPME. The application of heat treatment at 80 degrees C for 2 h did not change significantly the volatile composition of this honeydew.

Residues of azoxystrobin, fenhexamid and pyrimethanil in strawberry following field treatments and the effect of domestic washing.

Residues of the pesticides azoxystrobin, fenhexamid and pyrimethanil were determined in strawberry after field treatment. The effect of 'home' washing with tap water and a commercially available vegetable detergent on residue levels was also studied. After treatment, azoxystrobin and pyrimethanil residues on strawberry were on average 0.55 and 2.98 mg kg(-1), respectively, values below the maximum residue level (MRL) fixed by the European Union (2.0 and 5 mg kg(-1), respectively), while fenhexamid residues were on average 2.99 mg kg(-1), which is very close to the MRL of 3.0 mg kg(-1), but some samples were over the MRL. Thereafter, all residues declined, with a half-life of about 8 days (azoxystrobin and fenhexamid) and 4.8 days (pyrimethanil). Washing the fruit with tap water reduced the residues of azoxystrobin and fenhexamid but did not affect pyrimethanil residues. Finally, when fruits were washed with a commercial detergent, greater amounts were removed (about 45% of azoxystrobin and pyrimethanil and 60% of fenhexamid).