Honey as antimicrobial agent

Introduction

Antimicrobial agents (Greek anti, “against”; micro “tiny”, bio “life”) are chemical compounds used to eliminate or inhibit the growth of infectious microbes. The term antibiotics could be used instead of antimicrobial agents. The term antibiotic referred to only compounds from organic source (produced by bacteria or molds), which are toxic to other. In the latest development, the term is now used loosely to for both synthetic and semisynthetic organic compounds. Antibiotic generally refers to antibacterial agent; however, its loosely defined. It is preferable to specify compounds based on their target organism for example antimalarial, antiviral, or antiprotozoal.

_{By Doc. RNDr. Josef Reischig, CSc. - Author's archive, CC BY-SA 3.0, Link}

The base line for all antibiotics is selective toxicity: They are highly toxic to an invading organism than they are to an animal or human host. The first antibiotic was penicillin. Amoxicillin, ampicillin and benzylpenicilllin are examples of penicillin-derivative antibiotics widely used to treating enormous microbial infections.

Antimicrobial agents are very crucial and essential to combat the global burden of infectious diseases. However, the development and spread of bacteria resistance reduce the potency of antimicrobial agent especially antibiotics used as last resort. This consequently poses a serious threat to public health. Therefore, alternative strategies such as folklore medicine are of paramount importance and thus this situation has led to a re-evaluation of the therapeutic use of ancient remedies, such as plants and plant-based products.

Honey as an Antimicrobial Agent

Honey is a product produced naturally by honeybees. Production is usually from flower nectars or other secretions from living parts of plants. The nectars are collected, biologically transformed and combined with some gut materials. Thereafter, the resulting product is stored in the honeycomb where maturation takes place.

Currently, many researchers have reported that the antimicrobial property of honey with natural honey proven to poses broad spectrum activity when tested against infectious bacteria and other microbes especially in the treatment of wounds and food spoilage.

The use of honey as a therapeutic substance has been rediscovered and accepted as an antibacterial agent for treatment of different illnesses including ulcers, bed sore and surface wound infection, bacterial gastroenteritis especially in infants and liver disease.

_{Honey: image taken using infix X510}

Honey can be categorise based on colour, taste, viscosity etc. The Colour of honey forms a continuous range from very pale yellow through amber to darkish red amber to nearly black. The taste of honey also varies from sweet to bitter, depending largely on floral source (Nectar). The viscosity of honey is also a function of the condition of the climate at the time of the formation by the honeybees. For example, honeybees that fed on bitter kola (flora source) are expected to produce a bitter taste and black colouration. It is also expected that honey produced by the bees during the dry season are expected to be highly viscous while those produced during the rainy season are expected to be less viscous.

Mechanisms of Action

The mechanism behind the antimicrobial properties of honey has been studied by different researchers. Some of the active components in the substance that have been implicated in the antimicrobial properties of honey include hydrogen peroxide (H₂O₂), bee defensin-1, flavonoids, and a relatively low pH property. The different active components in honey have been isolated by neutralizing each one individually and observing the effect on its antimicrobial activity. Not all of the factors could be present in all types of honey, and these compounds have been recommended to be tested for and considered for clinical applications.

_{Flavonoid By Christian Becker - Own work using: BKChem & Inkscape, Public Domain, Link}

In addition to the active components and low pH, the osmolarity of honey is very high and has also been found to contribute to the inhibition of growth of organism, although this is true of sugar solutions as well. Honey has about 70 to 80% sugar and this high concentration could cause hypertonic conditions and consequently leading to lysis of microbial cell walls.

The hydrogen peroxide components is produced as bye-product through the action of an enzyme known as glucose oxidase. On dilution of honey, the enzyme breaks down the glucose in the honey to simpler product namely gluconic acid and hydrogen peroxide. Due to the slow release of H₂O₂, there is much less cytotoxic damage to the patient’s cells, providing a better method than applying H₂O₂ directly to wounds.

Bee defensin-1 was recently discovered in honey and is the only cationic bactericidal compound currently identified. When bee defensin-1 was also neutralized, the bactericidal activity was strongly reduced at 20% but was not affected at 30 and 40% honey solutions. This peptide is secreted by the hypopharyngeal gland of worker bees into collected nectar along with carbohydrate-metabolizing enzymes and bee defensin-1 presumably contributes to protection of royal jelly and honey against microbial spoilage.

Generally, flavonoids are a group of pigments usually produced by plants along with other pigments such as chlorophyll and xanthophyll. The presence of flavonoids has been hypothesized to contribute to the antimicrobial properties of honey. The mechanism of action of the pigment has been researched and found to include suppression of bacterial virulence, direct antibacterial activity as well as synergism with antibiotics. The direct antibacterial activity of flavonoids may be attributable to several tested mechanisms: cytoplasmic membrane damage (caused by perforation and/or a reduction in membrane fluidity possibly by generating hydrogen peroxide). There are 14 classes of flavonoids in total, categorized by their chemical nature and structure.

The low pH of honey has been attributed to the conversion of glucose into hydrogen peroxide and gluconic acid through the actions of glucose oxidase. The low pH has also been hypothesized to contribute to the bactericidal activity of honey.

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