Essential oils

Essential oils posses a distinct odour and are isolated from many different parts of the plant including the leaf, root, bark, flower, bud etc and are normally extracted by steam or hydro-distillation . These oils usually evaporate in the presence of air at moderate temperatures, thus explaining the use of the terms volatile or ertheral oils to describe such “essential” oils.

The term Essential was selected to describe these oils because they represent the “essence” i.e. the characteristic odour of the plant. (tanker et al 1990)

They have been around for thousands of years and have found a wide range of uses in society ranging from their use as aphrodisiacs to their use as an antibacterial. Traditionally plant extracts have been used in food preservation and are also widely used in the perfume industry. Interestingly plant extracts have also been used for the production of many drugs and

It has been documented by xxx that 98% of all drugs on the market are derived from plants (ref xx find)

Recently, many novel drugs such as the anti-malarial drug artemisin have been extracted from the artermisia plant (ref x)

And plant extracts have also been used to create novel cancer drugs aswell as new HIV drugs. (ref2)

With regards to essential oils, they have been used for their antiseptic i.e antibacterial/antifungal properties and therapeutic properties aswell as their aromatic properties. Fast tracking to the present day their uses remain the same, however with technological advancements in analytical chemistry much more is now understood in relation to their mechanism of action, particularly at the antimicrobial level. (Ref 2)

Long before the discovery of microorganisms, it was acknowledged that plants had certain therapeutic and healing properties especially the fact that they possessed antibacterial activity. This dates back to the time of the prophet muhammed (PBUh) who has mentioned that in black seed oil (an essential oil extracted from nigella seeds) has the cure for every illness except death (ref x) and thus certain oils have been used in the middles eastern subcontinent for many years.

However it is only in recent times that these properties have been understood and studied. (ref 3 and 4) Their preservative properties, however have been demonstrated and used for thousands of years.

The discovery of antibiotics such as penicillin from fungal sources and other more effective synthetic chemical drugs lead to a dramatic decline in the use of plant products for its antibiotic properties, but they are nevertheless still and sometimes exclusively used by some populations, furthermore there are many traditional herbalists who deal only in natural, herbal products.

We are now however witnessing a resurgence into the research of plant products as antimicrobials, as it is now widely understood that any antibiotic has a limited lifespan and due to the overreliance on such drugs and consequently over and unnecessary prescribing of antibiotics; antibiotic resistance has become a huge problem worldwide. There is a therefore a constant requirement to discover new antimicrobials to stop the spread of multi-drug resistant pathogens.

There has been a huge increase in to the research of traditional folk medicine in order to identify leads to develop novel therapeutic drugs more specifically antibiotics. Recent studies have suggested that numerous plant species have antimicrobial properties, and such plant based antibiotics have a huge therapeutic potential as they can help with the problem of antibiotic resistance and also exert their effects with fewer side effects that are often associated with synthetic antibiotics (ref 7)

Furthermore the interest in aromatherapy a branch of alternative medicine has made it a financially lucrative market for pharmaceutical companies to tap in to.

This rise in interest from pharmaceutical companies has had the effect of raising the profile of plant products as drugs as these companies pay particular attention to quality control, testing and are also subject to stringent regulation as are conventional drugs thus such drugs are deemed as “safe”

The therapeutic properties of essential oils have been well documented; results have been varied, with toxicity and side effects being very frequently implicated, and thus a possible explanation for their decline in use (REF 1) however due to reasons mentioned above we are now experiencing a rise in their use.

Extraction

The oils are extracted from various aromatic plants, in the main localized in temperature to warm countries such as those in the Middle East where they form a major part of the traditional pharmacopeia. They a numerous methods of extraction, which may include the use of liquid carob dioxide or microwaves, or more commonly distillation with use of steam or boiling water. Different methods are employed depending on the nature of the oil being extracted and the species from which it is being extracted from. For example in the extraction of Citrus oil steam distillation is preferred. However in other cases such as for use in the perfume industry the oil is extracted with lipophillic solvents.

Depending on the method used for extraction the chemical profile of the essential oil obtained will vary, and the method of extraction used will vary according to the purpose for which the essential oil wil be used eg in food preservation or perfume etc. (Ref 2)

The quality, quantity and composition of the essential oil extracted can vary according to the climate, composition of the soil, age of the plant and also the part of the plant from which it is extracted. (ref 2 Masotti et al 2003) so therefore in order to obtain an oil with a consistent composition it is imperative that the oil is extracted under the same conditions from the same part of the plant, that has been grown in the same soil under the same temperature. The majority of the essential oils used in industry are analysed using a combination of gas chromatography and mass spectrometry and analytical monographs can be obtained.

Chemical composition

Essential oils are naturally occurring complex mixtures which can contain anything from 20 -60 components at relatively different concentrations. However most essential oils have been identified as contain 2 or 3 major components that make up the bulk of the oil with the components being present in trace amounts. ( ref 2) For example geraniol and geranyl acetate have been found to be the main components of palmaros essential oil and citronelleol and geraniol are the major components of geranium essential oil. At it is usually these major components that are responsible for the biological properties of these oils.

In relation to the components that are associated with the antibacterial properties of these oils

The primary reason for choosing to study geranium oil is the fact that they has not been much research carried out on this particular oil, also the fact that this oil contains reasonable concentrations of terpeniods which generally posses antimicrobial properties. Furthermore recent studies have shown that geranium oil has showed prmosing antibacterial acivity against P-aerugios.

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