Manuka honey
Manuka honey (Leptospermum scoparium) is one of several floral honeys that has been shown by microbiology to have antibacterial activity and antimicrobial potential. The availability of manuka honey in different countries for research and development as a medicinal product has helped in the discovery of its antimicrobial activity.
Antibacterial activity of manuka honey
If manuka honey is to become a credible alternative to antibiotics, then microbiology needs to find the components that give manuka honey its antibacterial activity. Bacteria growth is prevented, in many cases, by the high sugar concentration, low pH and low water content of honey. These factors alone cannot explain fully the antibacterial activity of manuka honey.
Research by Allen, Molan and Reid (1991) surveyed 345 New Zealand honeys including manuka honeys from Leptospermum scoparium. Compared against known phenol standards, an agar diffusion assay for measuring antimicrobial activity in diluted honeys was used. The New Zealand honeys, including manuka honey, were diluted in water to measure hydrogen peroxide-derived activity and were diluted in catalase solution for non-hydrogen peroxide-derived activity. Allen and colleagues found in the laboratory that most honeys had some antibacterial activity plus some of the manuka honey samples (38%) had non-hydrogen peroxide-derived activity. From these results, it was argued that there are antimicrobial factors as well as high sugar concentration, low pH and generation of hydrogen peroxide.
In microbiology, scientific observations, for some time, have noted that there was an antibacterial compound in honey that was sensitive to temperature and light. This was identified as hydrogen peroxide. The effect of hydrogen peroxide on microbial cells was termed hydrogen peroxide-derived activity. Development of the potential of honey as a new antimicrobial agent for human use comes from the discovery that microorganisms are inhibited, without damage to cells and tissues, by the low concentration of hydrogen peroxide released slowly from some diluted honeys.
Composition of honey
Microbiologists are aware of the complexity of honey. Different geographical locations bring different physical characteristics and composition of honey. For example, jellybush honey in Australia is derived from a Leptospermum species like manuka honey in New Zealand. Both manuka honey and jellybush honey are non-hydrogen peroxide honeys. Jellybush honey and manuka honey have been involved in the discovery of new clinical applications of honey.
Identifying the antibacterial components of honey is difficult given how complex the composition of honey is and that the different substances may interact with each other. It is known that hydrogen peroxide, low pH and high sugar content are major components of the antibacterial activity of honey.
Honey-based products
Wound dressings impregnated with manuka honey (Leptospermum scoparium) are one of the growing number of honey-based products that have been approved in certain countries for clinical use. Other honey-based products being developed include hydrophilic gel for chronic and infected wounds, ointments for superficial wounds, honey based cream for irritation and minor wounds caused by eczema and honey-based products for dry or irritated skin.
The potential of manuka honey in the discovery of new antimicrobial agents continues in microbiology research to inform the development of honey-based products for clinical use.
Reference
Allen, KL., Molan, PC., Reid, GM., (1991) A Survey of the antibacterial activity of some New Zealand Honeys. Journal of Pharmacy and Pharmacology, 43:12,817-822
Susan Morris - Susan Morris, Scottish food and drink business manager, organic gardener, author and editor
