I thought I smelled something wrong when I read this passage from the abstract that Juanse posted:
"In most honey types, antimicrobial activity is due to the generation of hydrogen peroxide (H2O2)"
...as I posted before, I thought that the hygroscopic properties of honey were the most significant, not the peroxide content.
...so I downloaded the full study (for free):
http://www.frontiersin.org/Antimicrobials,_Resistance_and_Chemotherapy/10.3389/fmicb.2012.00265/full
...looking at the data, it showed ZERO antibacterial activity from the "osmotically equivalent" fake honey (17% water, the rest a mix of sugars). ...this can't be right, can it?
So, we look at the procedures, and find that for all the assays, the honey (including the fake honey/sugar solution) is diluted to 25% in water.
Obviously, this completely eliminates hygroscopic properties of all the samples.
"Fifty percent (w/v) of each honey sample, including the Comvita and the artificial honey, were prepared fresh for each assay in sterile deionized water, and incubated at 37°C with shaking at 200 rpm for 30 min to aid mixing. Diluted honey samples were then filter sterilized through 0.2 μm pore filters (Millipore) and mixed with equal volumes of either sterile deionized water for total activity testing, or freshly prepared 5600 U/mL catalase solution (Sigma-Aldrich, USA) for non-peroxide activity testing, to give a final concentration of 25% (w/v) honey. Aliquots of 100 μL of each solution were placed into wells of the assay plates."
So, when we look at this carefully, what we see is:
1. A claim that H2O2 is the source of antimicrobial activity in honey (it is a source of the antimicrobial activity, but I think it's orders of magnitude below that of the hygroscopic properties).
2. Methods were used to assay the antimicrobial properties of the honey that are designed to specifically eliminate any effect from the hygroscopic properties (no mention of this is made except when one reads the procedures...this is something that should have been noted conspicuously).
3. The claim in the abstract:
" all samples were significantly more active than an osmotically equivalent sugar solution."
...is misleading (I'm being kind here....it's dishonest). Yes, when you dilute the honey (and sugar syrup) to be 92% water, they are osmitically equivialant to each other, but none of this has anything to do with the properties of actual honey. Honey (or sugar syrup of 17% moisture) IS hygroscopic, and it does negatively affect bacterial growth. A 25% solution of honey (75% water) IS NOT HONEY.
So they have (without bothering to mention it) eliminated the most significant mechanism by which honey (or sugar syrup) inhibits bacterial growth, not mentioned that this mechanism is significant (or even exists at all):
"The primary antimicrobial component in most honeys is hydrogen peroxide (H2O2)...Certain honey types contain additional antimicrobial activity, which has been attributed to various different components including methylglyoxal (MGO), bee defensin-1, and other bee-derived compounds, florally derived phenolics, lysozyme, and other yet undetermined compounds"
...then used their data to claim that:
"Honey produced from native Australian flora has the potential for therapeutic use"
I don't know these researchers, and I don't know their work....but they claim no competing interests...yet, obviously, this whole study is the Austrailian equivalent to some of the manuka research (designed to help market manuka honey)...using Austrailain honey.
The data is actually interesting, and perhaps useful.
BUT
It is dishonest to completely ignore the hygroscopic properties of honey in the write up.
What a waste.
I can't even tell if this is peer reviewed...the information about the quality of the content of the journal is almost impossible to understand:
http://www.frontiersin.org/Antimicrobials,_Resistance_and_Chemotherapy/about
deknow
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