7th edition of European Pharmacopeia

 7^th edition of European Pharmacopeia

Introduction

According to the 7^th edition of European Pharmacopeia [1], Essential oils are described as “fragrant compounds, which have a complex composition and taken from the extraction of raw plant material. This extraction can be done either by dry distillation, steam distillation, or an appropriate mechanical method without heat application”. Commonly, a physical method is applied for the partition of essential oil from the aqueous phase that has no momentous alteration in its chemical structure. Various plant parts are used for the extraction of these oils, including vegetative and non-vegetative plant structures. Different techniques are applied for the extraction of these constituents [2]. These oils have lipophilic character, and because of low density and hydrophobic nature, these are organic solvents soluble. The yields of extracted oil is dependent on the plant species as well as on the part used. A very minimum yield as 1% indicates the extraction of a very rare but valuable component [1]. There are approximately 17,000 plant species; among them, about 10% belong to families of aromatic plants. [3]. Moreover, numerous essential oil genres are classified in several families, including Asteraceae, Cupressaceae, Lauraceae, Lamiaceae, Myrtaceae, Piperaceae, Poaceae, and Rutaceae [4]. The dissimilarities among chemical properties of essential oils are based on type and number and stereochemical structures of molecules. The chosen extraction process technique can assort these properties. The composition, quantity, and quality of extracted oils can be changed because of any factors including; age, cycle stage of plant life, plant organ, climate change, and composition of soil [5]. Furthermore, these essential oils are also known as secondary metabolites of plants having complicated mixtures of volatile organic compounds.

These natural compounds are hydrocarbon groups (sesquiterpenes, terpenes) and oxygenated groups (phenol ethers, lactones, phenols, aldehydes, ketones, esters, ethers, and alcohols) [6]. Usually, all types of essential oils have at least two to three vital constituents having the maximum concentrations (20-70%) contrasted to the other constituents existed in trace quantity. Such as, in Oraginum species, the essential oil comprises 27% of thymol and 30% of carvacol as main constituents. These constituents decide the biological features of these essential oils, while each of these constituents is placed in distinguishing groups having a distinct bio-synthetic origin. Derivatives of short-chain aliphatic hydrocarbon, phenylpropanoids, and terpenoids, are the most essential particular groups for some components in aromatic oils [6].

Attention in the appliance of these aromatic oils in different fields is continuously progressing. With their momentous pharmacological properties, these essential medicinal plants are being applied in pharmaceutical manufacturing as antifungal, antiviral, anti-inflammatory, antibacterial agents. Different researches have been done to evaluate the antimicrobial properties of these oils against different bacteria [1-3]. Additionally, psychiatrists also use these oils for psychic patients because of the affable odor produced by the essential plant’s oils [7]. Moreover, they insist on aromatic oils as food preservatives is expanding due to their biological property against foodborne pathogens, for example, Clostridium perfringens, Listeria monocytogenes, Pseudomonas putida, Salmonella typhimurium, and Staphylococcus aureus [8]. The issue of pathogens in meat and food products has been tackled by little dosage implementation of aromatic oils, as verified by several types of research [9]. There has been an amplified demand for the utilization of natural plants as a substitute for conventional antibiotics in the animal diet.  It is because of the expansion of antibiotic-resistant bacteria and their probable spreading from livestock to human beings. Indeed, the utility of synthetic antibiotics in the diet of animals has been banned by the European Union to encourage the healthy animal’s growth [10]. In pharmaceutical manufacturing, drugs in the form of sprays, creams, ointments, syrups, and capsules enclose some formulations of aromatic oils, and their manufacturing count is continuously increasing. Therefore, the utility of aromatic oils in various industries; cosmetics, pharmaceutical, and food are still under investigation to produce and formulate more competent products based on the essential oil. This review surrounds a detail of various extraction techniques involved in the extraction of essential oils and their constituents.

Extraction Techniques for Essential Oils

Various parts of different essential aromatic plants can be extracted and produce essential oils that consequently have many utilities in food safety, pharmaceutical, and cosmetics fields. The method used for extraction and manufacturing procedure for the extraction of essential oils is dependent on nature and constituent needed in the botanical extract. The significant aspect of ensuring the aromatic oil’s quality is the method applied for extraction since improper procedures for mining can be a source of destruction and diverge phytochemical’s action exists in fragrant oils. The consequential effects are capable of beings, such as the pharmacological component loss, stain effect, odor/off-flavor, and physical alteration of aromatic oils [2].

These oil extraction methods can be classified into two distinct classes: classical techniques and innovative techniques. The utilization of innovative approaches, for example, microwave and ultrasonic enhanced methods, has improved the competence of extraction methods in terms of time needed for extraction of the aromatic oil and energy indulgence, as well as upgrading in yield of production, and better quality of aromatic oils [1].