How Honey Kills Bacteria: Antibacterial, Antimicrobial and Antioxidant Properties of Honey

In particular, depending on the source of nectar, the organic substances in it form an antimicrobial and antioxidant system in honey. Due to this feature, it has been determined that honey has a lethal effect on many pathogenic bacteria, fungi, and viruses. Furthermore, the suppressive and exterminating effect of honey on antibiotic-resistant bacteria caused by nosocomial infections is of interest to scientists.

High bioactivity honey has been found to kill more than 20 species of pathogenic bacteria and antibiotic-resistant bacteria in a short time. Antibacterial, antimicrobial and antioxidant properties are the main causes of honey killing bacteria.

The Antibacterial Property of Honey

Since honey has an antibacterial property, microorganisms cannot survive and proliferate. In recent years, apitherapy, which is called treatment with rapidly developing bee products all over the world, uses bee venom, propolis, royal jelly, and pollen as well as honey. All bee products have general health and body resistance as well as therapeutic properties. The antibacterial properties of honey are due to its acidic structure, to a great extent due to the dry matter (sugar) and also the hydrogen peroxide, an antiseptic substance formed by the breakdown of glucose by enzymes. Honey, which contains high levels of sugar, shows an antibacterial effect by causing the water-borne microorganism to lose or die by losing water.

The high sugar concentration combined with the low water content causes osmotic stress, which prevents the deterioration of honey by micro-organisms. Slight dilution of honey may result in the growth of some yeasts, but even about 30-40% dilution of the sugar composition of the honey is sufficient to maintain its antibacterial activity. At higher dilution, the antibacterial activity results from other compounds rather than sugar. In the 1960s, hydrogen peroxide (H 2 O 2) was identified as an important antibacterial compound in honey. The glycosidase enzyme introduced by the honey bee into the nectars collected during the production of honey enables the conversion of glucose to H2O2 and glycolic acid. However, various honey has significant antibacterial properties due to their non-peroxide components. Recently, methylglyoxal and bee defensin-1 have been discovered as antibacterial compounds in honey in Manuka and RS honey, respectively. The pH of honey is usually between 3.5-4.5. This relatively acidic pH prevents many bacteria from growing in the environment of honey. In short, the antibacterial properties of honey are the result of low water content which causes osmosis, hydrogen peroxide effect, and high acidity.

Total phenol (TFI) in honey has shown to affect both antibacterial and antioxidant activity potential. Thus, the presence and amount of these compounds determine the antibacterial properties and thus the medicinal properties of honey. Therefore, the characterization of these organic compounds is important and necessary for the classification and price of honey according to the medical properties. This is very important as it will enable producers to make products based on this classification.

The antibacterial effect of honey is mainly due to the osmotic pressure generated by sugar which is approximately 76% in honey and the low pH (av. 3,9) caused by organic acids such as gluconic, butyric, acetic, formic, lactic, succinic, malic, citric and oxalic acids contained in honey (Özmen and Alkin, 2006; Anonymous, 2003). Hydrogen peroxide, which is formed as a result of oxidation of the glucose produced by the oxidase enzyme produced in the hypoferangial glands of bees, is defined as an inhibitor and stands out as one of the antibacterial compounds in honey (Gauhe, 1941). The level of hydrogen peroxide varies depending on the catalase activity from plants in honey.

While hydrogen peroxide is produced by glucose oxide in the honey or its fractions, the catalase enzyme in the medium breaks down hydrogen peroxide. Thus, it reduces the antibacterial effect caused by hydrogen peroxide (Snow and Manley-Harris, 2004). Polyphenols, phenolic acids (caffeic acid, ferulic acid, coumaric acid, ellagic acid, etc.) and their derivatives (methyl Syringate), aromatic acids, flavonoids, and recently Maillard reaction products have also been shown to be effective in the antibacterial activity of honey (Gauhe, 1941; White et al., 1962; Dustman, 1971; Molan, 1995; Bogdanow, 1997; Erdoğrul and Erbilir, 2007; Kwakman and Zaat, 2012). This explains the higher antibacterial activity of dark honey types containing high phenolic compounds compared to light honey types (Sarıkaya, 2009).

Honey has been shown to show inhibitory properties on the bacteria such as Escherichia coli, Staphylococcus aureus, Salmonella Enterica, Ser. Typhimurium, Bacillus subtilis, Pseudomonas Aeruginosa, Enterobacter cloaca, Micrococcus Luteus, and Klebsiella Pneomoniae with studies (Tomoi and Miyata, 2000). The effect of honey antibacterial activity on human health is due to the fact that it does not allow the development of these pathogens and deteriorating microorganisms and helps to heal infections (Özmen and Alkın, 2006). With this feature, honey is used in various ulcer treatments and treatments of wounds, burns, mouth, throat and bronchial infections (Krell, 1996).

The Antimicrobial Property of Honey

Researches have shown that mold, yeast, and bacterial spores may be present in low levels of honey, but vegetative bacteria are generally absent. However, honey generally has a low microbial load and long shelf life. Because of its antimicrobial properties, honey is seen as a natural food preservative (Mundo et al 2004). The antimicrobial activity of honey depends on its acidity, pH, osmotic pressure, and enzymatic hydrogen peroxide production via glucose oxidase. As additional honey components, aromatic acids or phenolic components may contribute to the antimicrobial activity as a whole. The cause of antibacterial activity observed in various honey samples was classified into four factors. These are inhibition due to high sugar concentration (low water activity), hydrogen peroxide formation, the presence of protein antimicrobial components and unidentified components (Mundo et al 2004).

The enzyme glucose oxidase contained in honey breaks down glucose into gluconic acid and hydrogen peroxide in the presence of water and oxygen. The resulting hydrogen peroxide and acidic environment protect honey during ripening and impart antimicrobial properties. Subsequently, the enzyme is inactive due to low pH, while hydrogen peroxide is decomposed by ascorbic acid and some ions into water and oxygen, which in turn causes the honey to be watered. Glucose oxidase is also damaged by heat and light. In one study, the loss of hydrogen peroxide production was observed by keeping the honey in the light for 10 minutes. Therefore, honey used for therapeutic purposes is not subjected to heat treatment. The bacterial spores that can be found in these honey are sterilized by gamma rays and their biological activities are protected.

Other properties of honey, except peroxide, are stable to heat and light and have maintained their activity for 6 months at room temperature. Therefore, honey with high phenolic content is more stable in terms of antimicrobial activity. In addition, the catalase enzyme in honey reduces the antimicrobial properties of honey by breaking down hydrogen peroxide (Lusby et al. 2002, Mundo et al. 2004, Snow and Manley-Harris 2004). The level of hydrogen peroxide in honey varies mainly depending on the catalase level from plants in honey. Hydrogen peroxide is produced by glucose oxide in honey or its fractions, and it has been found in laboratory studies that the catalase in the environment decreases its antimicrobial properties by degrading hydrogen peroxide (Snow and Manley-Harris 2004).

In microbiological analyzes conducted on 27 honey samples from different flora and geographical regions, Mundo et al (2004) found that honey showed inhibitory properties on 7 food-spoiling microorganisms (Alcaligenes Faecalis, Aspergillus niger, Bacillus Stearothermophilus, Geotrichum Candidum, Lactobacillus acidophilus, Penicillium Expansum, Pseudomonas Fluorescens) and 5 pathogens (Bacillus cereus, Escherichia coli O157: H7, Listeria monocytogenes, Salmonella Enterica, Ser. Typhimurium, ve Staphylococcus aureus) causing food poisoning. Inhibition effect was observed on Staphylococcus aureus. None of the samples inhibited mold growth. This inhibitory effect of honey is attributed to high sugar concentration (low water activity), production of hydrogen peroxide and protein components present in honey. Some antibacterial activities are linked to other undetectable components. The inhibitory effect of honey on the growth of microorganisms is highly variable. In this study, it was determined that this feature of honey is not related to a specific flora or region. The antimicrobial effect of honey on bacteria is not uniform and varies. In this study, hydrogen peroxide was found to be the most causative agent. Subsequent active substances were thought to be proteinaceous components.

In the study, it was found that the most sensitive microorganism susceptible to antimicrobial activity was B. stearothermophilus, where the least affected microorganisms were S. aureus, P. expansium, A. niger, G. candidum. B. stearothermophilus, a heat-resistant spore bacterium, was highly sensitive both on the surface and inside of the honey. Other susceptible bacteria were identified as A. faecalis and L. acidophilus. A. faecalis, L. acidophilus, and S. aureus ATCC 25923, 8095 and 9144 are sensitive to the antimicrobial activity of honey. The growth of E. coli, S. typhimurium and S. aureus ATCC 8095 honey is reduced due to the high osmotic pressure. Because of E. coli (0.96), Salmonella spp. (0.96), Psedomonas spp. (0.97), and Bacillus subtilis (0.95) may develop in water activities. Water activity in honey was between 0.920–0.945. However, P. fluorescens, B. stearothermophilus and B. cereus do not reduce their development in this water activity. Furthermore, the minimum water activity requirement of S. aureus is 0.86, which is considerably lower. Therefore, other factors are thought to play a role in the development of these bacteria besides water activity.

In a study, Allen et al. (2000) found that it has antibacterial properties on Methicillin-resistant Staphylococcus aureus and Vancomycin-resistant Escherichia coli.16, which are clinically important. Moreover, the presence of substances such as benzyl alcohol, 1,4-dihydroxybenzene, terpenes, and 2-hydroxybenzoic acid, low protein content and low redox potential also contribute to the antimicrobial properties of honey (Anonymous 2003a). Although it is known that the antimicrobial properties of honey originate from the presence of substances such as benzyl alcohol, 1,4-dihydroxybenzene, terpenes, and 2hydroxybenzoic acid, some scientists state whether the antimicrobial property is passed from honey to bee or nectar (Anonymous 2003b).

Honey is usually produced by honey bees (Apis mellifera). It has been found that honey produced by Melipona and Trigona genus honey bees belonging to Meliponinae subfamily have healing properties in tropical and semi-tropical regions. Honey produced by honeybees belonging to the Trigona family is generally considered to be a highly apitherapic product and is used as a drug against tens of diseases in Ethiopia. The honey of these bees is widely used in the treatment of stomach disorders, tonsillitis, cough, sore throat, stomach and intestinal ulcers, chilling, oral diseases, slimy structures and wound dressings (Garedew et al. 2004). Today, there are two types of honey that are used commercially for treatment purposes. These are Medihoney (Capilano, Australia13) obtained from Leptospermum Polygalifolium trees and Active Manuka Honey (New Zealand) honey from Leptospermum Scoparium trees. This honey typically has a high viscosity and is used as raw without heat treatment (Lusby et al. 2002).

The Antioxidant Property of Honey

Honey is known to have many antioxidant compounds. These compounds are naturally present in honey. Bioactive substances are transported to the honey by bees from plants, which are the main source of the components that synthesize phytochemicals that have antioxidant properties such as the leaves and fruits of fruit trees and destroy free radicals. Generally, honey contains four groups of substances with antioxidant activity such as polyphenols (flavonoids) or phenolic compounds, enzymes, ascorbic acid, and peptides.

Flavonoids exhibit antioxidant properties in many different ways by retaining free oxygen species, reducing radicals such as alkoxy radicals and peroxide radicals, inhibiting enzymes that produce superoxide anions, and inhibiting transition-containing enzymes that produce oxidation reactions. In the study conducted on 3 honey (chestnut, rhododendron, heterofloral) in Anatolia, the amount of phenolic compound of honey was found as chestnut honey, heterofloral and Rhododendron honey, respectively.

Antioxidant capacities of 7 species of honey (Heather, Oak, Chestnut, Pine, Geven, Acacia, Lavender) were examined Copper (II) Ion Reducing Antioxidant Capacity (CUPRAC) method in a study. Oak and chestnut honey show the highest antioxidant capacity, where pine and heather honey follow them. When the total phenolic content was examined, it was observed that the heather honey has the highest content. Acacia honey has the lowest total phenolic content when compared with other honey. While the antioxidant capacity of chestnut and oak honey is the highest, heather honey has the highest total phenolic compound because it has antioxidant properties in non-phenolic compounds besides phenolic compounds.

Antioxidants are compounds that inhibit or prevent free radical oxidation of various organic compounds at low concentrations. In recent years, synthetic antioxidants have been considered carcinogenic and therefore, interest in natural antioxidants of plant origin has increased. Honey, a nutrient obtained from extracts collected from plants, draws attention as a potential antioxidant (Rice-Evans, 1997). Honey, consisting of approximately 200 compounds, average 20% moisture, 76% sugar, 0.18% ash, 1% total polyphenol, protein as well as components such as α-tocopherol, ascorbic acid, flavonoids (chrysin, pinocembrin, quercetin, galantine, kaempferol, hesperetin, mirsetine) and other phenolic acids (caffeic, coumaric, elliptic, ferulic, chlorogenic), glucose oxidase, catalase, and peroxidase include enzymes (White, 1979; Bertoncelj et al., 2007).

There is a positive relationship between antioxidant activity and total phenolic content of honey and antioxidant activity is mainly caused by phenolic compounds. It is known that phenolic compounds abundant in dark honey show stronger antioxidant activity than ascorbic acid or vitamin E (Sarıkaya, 2009). Flavonoids and phenolic acids, which are the most abundant phenolic compounds in honey, have an antibacterial, anti-inflammatory, anti-allergic and anti-thrombotic effect, and have been shown to play an important role in cardiovascular diseases and cancer treatments (Al-Habari et al., 2002; Pyrzynska. and Biesaga, 2009; Miotto, 2010).

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Savaş Ateş

I like eating honey a lot. We have a huge interest in bees and how they make honey. I have visited honey farms. I have talked to a lot of honey sellers. I read a lot of books about them. I want to share my knowledge with you.

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