Polyphenols Needed for Honey Antibacterial Effect

Why does honey heal wounds? Its antibacterial activity is due to its ability to produce Hydrogen Peroxide and now this Canadian study identifies the cause. Thanks to honeybees collecting nectar from flowers, these important polyphenols remain in honey, eliminating the notion that artificial honey is just as good...

Unraveling a Mechanism of Honey Antibacterial Action: Polyphenol/H2O2-Induced Oxidative Effect on Bacterial Cell Growth and on DNA Degradation

FoodChemistry, 24 January 2012

Several compounds with antibacterial activities were identified in honey. However, a mechanism by which they lead to bacterial growth inhibition and bacterial death remains still unknown.

We recently found that honeys possess DNA degrading activity mediated by honey hydrogen peroxide and an unknown honey component(s). Here we provide evidence that active honeys (MIC90 of 6.25% to 12.5% v/v) possessed significantly higher levels of phenolics (p<0.02) of higher radical scavenging activities (p<0.005) than honeys of average activity.

Removal of H2O2 by catalase eliminated bacteriostatic activities caused by both phenolics and H2O2 suggesting that the growth inhibition resulted from the coupling chemistry between these compounds. Both phenolics and H2O2 were involved in DNA degradation by honeys. Treatment of plasmid DNA with H2O2 alone did not affect the DNA integrity but H2O2 removal from honey by catalase prevented DNA degradation. Polyphenols extracted from honeys degraded plasmid DNA in the presence of H2O2 and Cu (II) in the Fenton-type reaction. The extent of DNA degradation was inversely related to the polyphenol concentration in this system as well as in honeys. At low content, honey polyphenols exerted pro-oxidant activity damaging to DNA.

In conclusion, honey phenolics with pro-oxidant activities were necessary intermediates that conferred oxidative action of H2O2. Phenolic/H2O2-induced oxidative stress constituted the mechanism of honey bacteriostatic and DNA damaging activities.

Highlights: 

► A coupling chemistry between polyphenols and H2O2 was the mechanism underlying DNA degradation by honey. 
► Honey polyphenols emerged as active intermediates that were necessary to confer oxidative action of hydrogen peroxide. 
► The antioxidant/prooxidant properties of honey polyphenols play a critical role in bacterial DNA degradation. 

Mexican Honeys Prove Antioxidant, Antibacterial Action

It's reassuring to see Mexican researchers contributing to the body of science confirming the antibacterial and antioxidant properties in honey. Nutritionally speaking, I've often found Mexican Honey to be very flavorful, aromatic and with lots of tropical notes.  

Quality Parameters and Antioxidant and Antibacterial Properties of Some Mexican Honeys

J Food Science, 2011 Dec 2

A total of 14 Mexican honeys were screened for quality parameters including color, moisture, proline, and acidity. Antioxidant properties of complete honey and its methanolic extracts were evaluated by the DPPH, ABTS, and FRAP assays. In addition, the antimicrobial activity of complete honeys against Bacillus cereus ATCC 10876, Listeria monocytogenes Scott A, Salmonella Typhimurium ATCC 14028, and Sthapylococcus aureus ATCC 6538 was determined.

Most of honeys analyzed showed values within quality parameters established by the Codex Alimentarius Commission in 2001. Eucalyptus flower honey and orange blossom honey showed the highest phenolic contents and antioxidant capacity. Bell flower, orange blossom, and eucalyptus flower honeys inhibited the growth of the 4 evaluated microorganisms. The remaining honeys affected at least 1 of the estimated growth parameters (increased lag phase, decreased growth rate, and/or maximum population density). Microorganism sensitivity to the antimicrobial activity of honeys followed the order B. cereus; L. monocytogenes; Salmonella Typhimurium; S. aureus.

The monofloral honey samples from orange blossoms, and eucalyptus flowers demonstrated to be good sources of antioxidant and antimicrobial compounds. All the Mexican honey samples examined proved to be good sources of antioxidants and antimicrobial agents that might serve to maintain health and protect against several diseases. 

Practical Application: 

The results of the study showed that Mexican honeys display good quality parameters and antioxidant and antimicrobial activities. Mexican honey can be used as an additive in the food industry to increase the nutraceutical value of products.

Basque Propolis Has Strong Activity Against Microbial Strains

Exciting new results of propolis antimicrobial and antifungal action against Staphylococcus aureus, Candida albicans and Salmonella enterica ...

The Antimicrobial Effects of Propolis Collected in Different Regions in the Basque Country (Northern Spain)

WorldJournal of Microbiology and Biotechnology, Nov 2011

The antimicrobial activity of 19 propolis extracts prepared in different solvents (ethanol and propylene glycol) (EEP/PEP), was evaluated against some bacterial and fungal isolates using the agar-well diffusion method.

It was verified that all the samples tested showed antimicrobial activity, although results varied considerably between samples. Results revealed that both types of propolis extracts showed highly sensitive antimicrobial action against Gram-positive bacteria and fungi at a concentration of 20% (Staphylococcus aureus, Streptococcus mutans, Candida albicans and Saccharomyces cerevisae) with a minimal inhibitory concentration (MIC) ranging from 0.5 to 1.5 mg/ml, with a moderate effect against Streptococcus pyogenes (MIC from 17 to 26 mg/ml).

To our knowledge, this is the first study showing elevated antimicrobial activity against Gram-negative bacteria [Salmonella enterica (MIC from 0.6 to 1.4 mg/ml)] and lesser activity against Helicobacter pylori (MIC from 6 to 14 mg/ml), while Escherichia coli was resistant.

This concluded that the Basque propolis had a strong and dose-dependent activity against most of the microbial strains tested, while database comparison revealed that phenolic substances were responsible for this inhibition, regardless of their geographical origin and the solvent employed for extraction. Statistical analysis showed no significant differences between EEP and PEP extracts.