Indeed, medicinal importance of honey has been documented in the world's oldest medical literatures, and since the ancient times, it has been known to possess antimicrobial property as well as wound-healing activity. The healing property of honey is due to the fact that it offers antibacterial activity, maintains a moist wound condition, and its high viscosity helps to provide a protective barrier to prevent infection. Its immunomodulatory property is relevant to wound repair too. The antimicrobial activity in most honeys is due to the enzymatic production of hydrogen peroxide. However, another kind of honey, called non-peroxide honey (viz., manuka honey), displays significant antibacterial effects even when the hydrogen peroxide activity is blocked. Its mechanism may be related to the low pH level of honey and its high sugar content (high osmolarity) that is enough to hinder the growth of microbes. The medical grade honeys have potent in vitro bactericidal activity against antibiotic-resistant bacteria causing several life-threatening infections to humans. But, there is a large variation in the antimicrobial activity of some natural honeys, which is due to spatial and temporal variation in sources of nectar. Thus, identification and characterization of the active principle(s) may provide valuable information on the quality and possible therapeutic potential of honeys (against several health disorders of humans), and hence we discussed the medicinal property of honeys with emphasis on their antibacterial activities.
Keywords: Honey, Antibacterial activity, Wound healing property, Glucose oxidase, Non-peroxide effect, Medical-grade honey, Antimicrobial agents, Medicinal property, Antimicrobial property, Immunomodulatory property
Antimicrobial agents are essentially important in reducing the global burden of infectious diseases. However, as resistant pathogens develop and spread, the effectiveness of the antibiotics is diminished. This type of bacterial resistance to the antimicrobial agents poses a very serious threat to public health, and for all kinds of antibiotics, including the major last-resort drugs, the frequencies of resistance are increasing worldwide,. Therefore, alternative antimicrobial strategies are urgently needed, and thus this situation has led to a re-evaluation of the therapeutic use of ancient remedies, such as plants and plant-based products, including honey–.
The use of traditional medicine to treat infection has been practiced since the origin of mankind, and honey produced by Apis mellifera (A. mellifera) is one of the oldest traditional medicines considered to be important in the treatment of several human ailments. Currently, many researchers have reported the antibacterial activity of honey and found that natural unheated honey has some broad-spectrum antibacterial activity when tested against pathogenic bacteria, oral bacteria as well as food spoilage bacteria,. In most ancient cultures honey has been used for both nutritional and medical purposes. The belief that honey is a nutrient, a drug and an ointment has been carried into our days, and thus, an alternative medicine branch, called apitherapy, has been developed in recent years, offering treatments based on honey and other bee products against many diseases including bacterial infections. At present a number of honeys are sold with standardized levels of antibacterial activity. The Leptospermum scoparium(L. scoparium) honey,the best known of the honeys, has been reported to have an inhibitory effect on around 60 species of bacteria, including aerobes and anaerobes, gram-positives and gram-negatives. Tanet al reported that Tualang honey has variable but broad-spectrum activities against many different kinds of wound and enteric bacteria. Unlike glucose oxidase, the antibacterial properties fromLeptospermum spp. honeys are light- and heat-stable. Natural honey of other sources can vary as much as 100-fold in the potency of their antibacterial activities, which is due to hydrogen peroxide,. In addition, honey is hygroscopic, which means that it can draw moisture out of the environment and dehydrate bacteria, and its high sugar content and low level pH can also prevent the microbes from growth.
Based upon the extensive searches in several biomedical science journals and web-based reports, we discussed the updated facts and phenomena related to the medicinal property of honeys with emphasis on their antibacterial activities in this review.
2. Medicinal property
Honey is an ancient remedy for the treatment of infected wounds, which has recently been ‘rediscovered’ by the medical profession, particularly where conventional modern therapeutic agents fail. The first written reference to honey, a Sumerian tablet writing, dating back to 2100-2000 BC, mentions honey's use as a drug and an ointment. Aristotle (384-322 BC), when discussing different honeys, referred to pale honey as being “good as a salve for sore eyes and wounds”. Manuka honey has been reported to exhibit antimicrobial activity against pathogenic bacteria such as Staphylococcus aureus (S. aureus) andHelicobacter pylori (H. pylori) making this honey a promising functional food for the treatment of wounds or stomach ulcers.
The honey has been used from ancient times as a method of accelerating wound healing, and the potential of honey to assist with wound healing has been demonstrated repeatedly,. Honey is gaining acceptance as an agent for the treatment of ulcers, bed sores and other skin infections resulting from burns and wounds,. The healing properties of honey can be ascribed to the fact that it offers antibacterial activity, maintains a moist wound environment that promotes healing, and has a high viscosity which helps to provide a protective barrier to prevent infection. There are many reports of honey being very effective as dressing of wounds, burns, skin ulcers and inflammations; the antibacterial properties of honey speed up the growth of new tissue to heal the wound. The medihoney and manuka honey have been shown to have in vivo activity and are suitable for the treatment of ulcers, infected wounds and burns,.
The honey, when applied topically, rapidly clears wound infection to facilitate healing of deep surgical wounds with infection. The application of honey can promote the healing in infected wounds that do not respond to the conventional therapy, i.e., antibiotics and antiseptics, including wounds infected with methicillin-resistant S. aureus,. Moreover, it can be used on skin grafts and infected skin graft donor sites successfully.
The manuka, jelly bush and pasture honeys are capable of stimulating the monocytes, the precursors of macrophages, to secrete TNF-α,. On the other hand, glycosylated proteins can induce TNF-α secretion by macrophages, and this cytokine is known to induce the mechanism of wound repairing.Furthermore, the ability of honey to reduce ‘reactive intermediates release’ may well limit tissue damage by activated macrophages during wound healing. Thus, the immunomodulatory property of honey is relevant to wound repair.
The support for using honey as a treatment regimen for peptic ulcers and gastritis comes from traditional folklore as well as from reports in modern times. Honey may promote the repair of damaged intestinal mucosa, stimulate the growth of new tissues and work as an anti-inflammatory agent,. Raw honey contains copious amounts of compounds such as flavonoids and other polyphenols which may function as antioxidants. Clinical observations have been reported of reduced symptoms of inflammation when honey is applied to wounds. The removal of exudate in wounds dressed with honey is of help in managing inflamed wounds.
3. Antibacterial activity
3.1. Potential antibacterial agent
The use of honey as a traditional remedy for microbial infections dates back to ancient times. Research has been conducted on manuka (L. scoparium) honey, which has been demonstrated to be effective against several human pathogens, including Escherichia coli (E. coli), Enterobacter aerogenes, Salmonella typhimurium, S. aureus,. Laboratory studies have revealed that the honey is effective against methicillin-resistant S. aureus (MRSA), β-haemolytic streptococci and vancomycin-resistant Enterococci(VRE),. However, the newly identified honeys may have advantages over or similarities with manuka honey due to enhanced antimicrobial activity, local production (thus availability), and greater selectivity against medically important organisms. The coagulase-negative staphylococci are very similar to S. aureus, in their susceptibility to honey of similar antibacterial potency and more susceptible than Pseudomonas aeruginosa (P. aeruginosa) and Enterococcus species.
The disc diffusion method is mainly a qualitative test for detecting the susceptibility of bacteria to antimicrobial substances; however, the minimum inhibitory concentration (MIC) reflects the quantity needed for bacterial inhibition. Following the in vitro methods, several bacteria (mostly multidrug resistant; MDR) causing human infections that were found susceptible to honeys are presented in Table 1.