Honey: Chemical Components. Actions

Historical Note

Honey has been used since ancient times as a healing agent for wounds and a treatment for gastric complaints. In ancient Greece, Hippocrates recommended honey and vinegar for pain and honey combinations for fever. It is also recommended by the Bible and Koran as a medicinal agent. Over the past few decades, scientific research has confirmed its role as a successful wound treatment. It is also known as honig and miel blanc.

Chemical Components

Caffeic acids, benzoic acid and its esters, phenolic acid and its esters, flavanoids, beeswax, inhibin, glucose oxidase and catalase, although other as yet unidentified constituents also exist.

The composition of a particular honey greatly depends on the composition of the nectar it originated from, and therefore the plant species involved in its production.

Main Actions

ANTIBACTERIAL

The type of plant species involved in honey production is significant, as some confer greater antibacterial properties than others. Currently, evidence suggests honey produced from the tea trees Leptospermum scoparium (New Zealand manuka) and Lipolygalifolium (Australian jelly bush) are the most effective, but batch testing is still required to verify the antibacterial activity of commercially produced preparations. However, other honeys, not specifically promoted for their anti-bacterial qualities, may still have antibacterial activity.

Several mechanisms of action account for the antibacterial effect of honey.

Hydrogen peroxide content

Hydrogen peroxide has antiseptic properties and is naturally produced in honey. The relative levels of two enzymes, glucose oxidase and catalase, within honey influence the amount of hydrogen peroxide produced. Additionally, diluting full-density honey encourages greater hydrogen peroxide and gluconic acid production from glucose. Differences in antimicrobial activity among honeys from various floral sources may, in part, be a reflection of these natural variations.

High osmolarity

Honey has a high sugar and low water content, with sugar concentration reaching up to 80% in some seasons. Its high osmolarity is considered important because sugar molecules bind existing water molecules, thereby reducing the amount of water available to bacteria.

Low pH Honey is an acidic substance and therefore unfavourable to the growth of certain bacteria. In vitro testing shows that Leptospermum honey can inhibit the growth of several important bacterial pathogens, including Escherichia coli, Salmonella typhimurium, Shigella sonnei, Listeria monocytogenes, Staphylococcus aureus, Bacillus cereusand Streptococcus mutans.

Honey has also been tested for efficacy against a range of drug-resistant bacteria, with positive results. Eighteen strains of methicillin-resistant Staphylococcus aureus and 27 strains of vancomycin-sensitive and resistant enterococci isolated from infected wounds and hospital surfaces were sensitive to concentrations below 10% w/v of manuka honey and pasture honey. Artificial honey was also effective, but concentrations three times greater were required to produce similar results.

Phenolic compounds

The antioxidant activity of honey has been associated with the levels of phenolic compounds found in a range of floral honeys, with antioxidant activity varying between 43.0% and 95.7%. The responsible compounds suggested include p-coumaric acid, kaempferol, chrysin and apigenin. The variation in the concentration of the phenolic compounds between different floral honeys is further confirmed through another study, which found millefiori honey highest in polyphenols, flavonoids, and a corresponding high antioxidant activity, when compared with Acacia honey.

DEODORISES WOUNDS

Bacteria use the glucose found in honey in preference to amino acids, thereby producing lactic acid instead of malodorous products.

DEBRIDING

The topical application of honey to a wound tends to lift debris to the surface, allowing for easier cleaning, which may be related to its high osmolarity. Honey does not adhere to the surface, allowing for easier and less painful wound dressing changes.

ENHANCES WOUND HEALING

Clinical evidence suggests that the application of honey hastens granulation and epithelialisation of necrotic tissue by various mechanisms. It appears to stimulate the growth of new blood capillaries and cytokine production, thereby stimulating tissue regeneration. The high viscosity of honey and its hygroscopic character allows it to form a physical barrier, creating a moist environment and a reduction in local oedema. Clinically, it appears that epithelialisation is accelerated between day 6 and 9, and that honey is more beneficial than EUSOL as a wound dressing agent.

ANTIOXIDANT

The phenolic compounds found in honey, namely the flavonoids, render it a good source of antioxidants. In vitro tests have confirmed a significant link between absorbance and antioxidant power, with darker, more opaque honeys having stronger antioxidant power than lighter, clearer honeys. More specifically, manuka honey has been identified to be a specific scavenger of superoxideanions.

IMMUNOMODULA TION

An animal study has shown that both immunocompetent and immunodeficient mice had increased humoral immunity following administration with honey.

Other Actions

An in vitro study showed that honey prevented binding of Salmonella interiditis to intestinal epithelial cells at dilutions of up to 1:8.

Preliminary studies suggest honey may have an impact on reducing the intoxicating effects of alcohol; however, that research was of questionable quality, and a better standard of research is required to validate this effect.

Honey may also have an antimutagenic activity against a common food carcinogen and mutagen Trp-p-1.