NATURAL ESSENTIAL OILS FROM EXTRACTION TO …

www.wjpps.com Vol 6, Issue 7, 2017.

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Thakur et al. World Journal of Pharmacy and Pharmaceutical Sciences

NATURAL ESSENTIAL OILS FROM EXTRACTION TO

ENCAPSULATION

Thakur P.*, Kapila P., Sharma R.B., Agarwal S. and Vashist H.

LR Institute of Pharmacy, Solan (H.P.), 173223.

ABSTRACT

Essential oils are natural products which have many interesting

applications. Extraction of essential oils from plants is performed by

classical and innovative methods and that are obtained from various

parts of the plants such as flowers, leaves, or bark by steam

distillation, expression, or extraction, that are usually mixtures

of compounds such as aldehydes or esters, and that are used

often in the form of essences in perfumes, flavorings and

pharmaceutical preparations. Many encapsulation processes have

been developed and reported in the literature in order to encapsulate biomolecules, active

molecules, nanocrystals, oils and also essential oils for various applications such as in vitro

diagnosis, therapy, cosmetic, textile, food etc. Essential oils encapsulation led to various new

formulations with new applications. This maintains the protection of the oil and controlled

release. The most commonly prepared carriers are polymer particles, liposomes and solid

lipid nanoparticles.

KEYWORDS: Essential oils are nanocrystals, solid lipid nanoparticles.

INTRODUCTION

Essential oils are highly concentrated substances extracted from flowers, leaves, stems, roots,

seeds, barks, resins, or fruit rinds. These oils are often used for their flavor and their

therapeutic or odoriferous properties, in a wide selection of products such as foods, medicines

and cosmetics. Extraction of essential oils is one of the most time- and effort-consuming

processes.[1]

Essential oils are largely composed of terpenes and aromatic polypropanoid

compounds derived from the acetate-mevalonic acid and the shikimic acid pathways,

respectively. Essential oil composition of plants varies and is due to genetic and

environmental factors that influence genetic expression.[2]

Essential Oils have added a lot of

WORLD JOURNAL OF PHARMACY AND PHARMACEUTICAL SCIENCES

SJIF Impact Factor 6.647

Volume 6, Issue 7, 488-518 Review Article ISSN 2278 – 4357

Article Received on

16 May 2017,

Revised on 06 June 2017, Accepted on 26 June 2017,

DOI: 10.20959/wjpps20177-9626

*Corresponding Author

Thakur P.

LR Institute of Pharmacy,

Solan (H.P.), 173223.


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value to the growth of flavor and fragrance industry as well as agriculture. The economy of

the country being agriculture based, its farmers were engaged in traditional agriculture

growing mostly food crops, which has caused them low returns. Imperative need has,

therefore, been felt of growing essential oil bearing crops for a long time past, under

diversified farming programme which have proved to be cash crops offering much better

returns to the farmers. In our country, some 1300 species are known to contain Aromas, but

only about 50 of these plants and oils derived from them are in consistent demand in trade &

industry.[3]

The therapeutic potential of essential oils, like other plant-derived remedies, has

yet to be fully realized. Although numerous medical herbs have been utilized since antiquity,

many of which have been exploited to provide the biologically active compounds which form

the basis for most of our modern drugs (such as quinine and cocaine), there is still a great

deal to be learnt about their precise pharmacology. This is particularly true of aromatic oils,

which by their very nature have such a concentrated yet multifaceted make-up. In addition,

„only a small proportion of the world flora has been examined for pharmacologically active

compounds, but with the ever-increasing danger of plants becoming extinct, there is a real

risk that many important plant sources may be lost.[4]

The essential oil content of plant tissue

also varies with developmental stage and can vary by extraction methods.[2]

Essential oils are

also known as volatile oils, ethereal oils, aetherolea, or simply as the oil of the plant from

which they were extracted. An oil is "essential" in the sense that it contains the "essence of"

the plant's fragrance-the characteristic fragrance of the plant from which it is derived.[5]

Essential oils are composed by lipophilic substances, containing the volatile aroma

components of the vegetal matter, which are also involved in the defense mechanisms of the

plants. The essential oil represent a small fraction of plant composition and is comprised

mainly by monoterpenes and sesquiterpenes and their oxygenated derivatives such as

alcohols, aldehydes, ketones, acids, phenols, ethers, esters, etc.[6]

Techniques commonly

employed for extracting essential oils include hydrodistillation, steam distillation, solvent

extraction head space analysis and liquid CO2 extraction. The composition of the extracted

oil may vary from one extraction method to another.[2]

The power of herbals and essential oils

lies in the combination of their elements and the trace components are every bit as important

as their main constituents. In fact, it seems to be that the minor constituents have a controlling

and strengthening effect on the main constituents. Many of these trace elements enable the

herbal or oil to heal more efficiently and without the nasty side effects experienced when

using the synthetic reconstructions (drugs or oils) that do not contain the trace elements.

With pure essential oils and herbal medicines in their complete state.


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You can heal and nourish without the traditional side effects of drugs![7]

Essential oil is used in perfumery, aromatherapy, cosmetics, incense, medicine, household

cleaning products and for flavoring food and drink. They are valuable commodities in the

fragrance and food industries. More than 250 types of essential oils. A number of countries

produce different kinds of essential oils. India ranks second in the world trade of essential oil.

Essential oils are derived from various sections of plants. An essential oil is usually separated

from the aqueous phase by a physical method that does not lead to significant change in its

chemical composition. Essential oils could be then subjected to an appropriate further

treatment. Essential oils are oily aromatic liquids extracted from aromatic plant materials.

They could be biosynthesized in different plant organs as secondary metabolites.[8]

Literature Review

Sukhdev Swami Handa et al. 2008. reviewed on the extraction technologies for medicinal

and aromatic plants. A wide range of technologies is available for the extraction of active

components and essential oils from medicinal and aromatic plants. The choice depends on the

economic feasibility and suitability of the process to the particular situation. The various

processes of production of medicinal plant extracts and essential oils are reviewed in this

paper.

Virendra P. S. Rao et al., 2006-7. reviewed on Extraction of Essential oils and its

Applications. Essential oils are highly concentrated substances extracted from flowers,

leaves, stems, roots, seeds, barks, resins, or fruit rinds. These oils are often used for their

flavor and their therapeutic or odoriferous properties, in a wide selection of products such as

foods, medicines, and cosmetics. Extraction of essential oils is one of the most time- and

effort-consuming processes. The way in which oils are extracted from plants is important

because some processes use solvents that can destroy the therapeutic properties. There are

wide number of ways to extract the Essential oil but the quality never remains the same. Here

we are using the “Steam Distillation” method for extraction which is the cheapest way for the

extraction of Oils from the different parts of the plants.

Farid Chemat et al., 2012. reviewed on Green Extraction of Natural Products: Concept and

Principles. The design of green and sustainable extraction methods of natural products is

currently a hot research topic in the multidisciplinary area of applied chemistry, biology and

technology. Here in we aimed to introduce the six principles of green-extraction, describing a


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multifaceted strategy to apply this concept at research and industrial level. The mainstay of

this working protocol are new and innovative technologies, process intensification, agro-

solvents and energy saving. The concept, principles and examples of green extraction here

discussed, offer an updated glimpse of the huge technological effort that is being made and

the diverse applications that are being developed.

Opender Koul et al., 2008. has done study on Essential oil as Green Pesticides: Potential and

Contraints. Plant pathogenic fungi ranging from insecticidal, antifeedant, repellent,

oviposition deterrent, growth regulatory and antivector activities. These oils also have a long

tradition of use in the protection of stored products. Recent investigations indicate that some

chemical constituents of these oils interfere with the octopaminergic nervous system in

insects. As this target site is not shared with mammals, most essential oil chemicals are

relatively non-toxic to mammals and fish in toxicological tests and meet the criteria for

“reduced risk” pesticides. Some of these oils and their constituent chemicals are widely used

as flavoring agents in foods and beverages and are even exempt from pesticide registration.

Essential oils and their volatile constituents are used widely to prevent and treat human

disease. The possible role and mode of action of these natural products is discussed with

regard to the prevention and treatment of cancer, cardiovascular diseases including

atherosclerosis and thrombosis, as well as their bioactivity as antibac-terial, antiviral,

antioxidants and antidiabetic agents. Their application as natural skin penetration enhancers

for transdermal drug delivery and the therapeutic properties of essential oils in aroma and

massage therapy will also be outlined.

J. Azmir et al., 2013. experimented on Techniques for extraction of bioactive compounds

from plant materials. The use of bioactive compounds in different commercial sectors such as

pharmaceutical, food and chemical industries signifies the need of the most appropriate and

standard method to extract these active components from plant materials. Along with

conventional methods, numerous new methods have been established but till now no single

method is regarded as standard for extracting bioactive compounds from plants. The

efficiencies of conventional and non-conventional extraction methods mostly depend on the

critical input parameters; understanding the nature of plant matrix; chemistry of bioactive

compounds and scientific expertise. This review is aimed to discuss different extraction

techniques along with their basic mechanism for extracting bioactive compounds from

medicinal plants.


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Tiziana Fornari et al., reviewed on Isolation of essential oil from different plants and herbs

by supercritical fluid extraction. Supercritical fluid extraction (SFE) is an innovative, clean

and environmental friendly technology with particular interest for the extraction of essential

oil from plants and herbs. Supercritical CO2 is selective, there is no associated waste

treatment of a toxic solvent, and extraction times are moderate. Further supercritical extracts

were often recognized of superior quality when compared with those produced by hydro-

distillation or liquid-solid extraction. This review provides a comprehensive and updated

discussion of the developments and applications of SFE in the isolation of essential oils from

plant matrices. SFE is normally performed with pure CO2 or using a cosolvent; fractionation

of the extract is commonly accomplished in order to isolate the volatile oil compounds from

other co-extracted substances.

Lili Xu et al. 2011. experimented on Recent advances on supercritical fluid extraction of

essential oils. Supercritical fluid extraction (SFE) is one of the most commonly used

extraction techniques in the course of analysis or preparation. It is environmentally friendly

and has some advantages over other conventional extraction methods. This review covers the

recent developments of SFE in the extraction of essential oils from the plant materials during

the period 2005 to 2011, in particular some factors influencing SFE extraction yield, its

characteristics and applications.

Muhammad Syarhabil Ahmad et al. 2014. experimented on Novel Closed System

Extraction of Essential Oil: Impact on Yield and Physical Characterization. We have

developed an extraction technique derived from the purification technique of bulb to bulb

distillation, a novel and green approach for the extraction of essential oil from fresh plant

materials. This solvent and water free approach is based on a simple principle involving the

application of vacuum system in a closed system under a reduced pressure and temperature to

extract essential oils. The extraction has been compared with a conventional technique, hydro

distillation. Essential oil isolated by solvent free extraction were quantitatively (yield) and

qualitatively (aromatic profile) better to those obtained by hydro distillation. The present

apparatus permits fast and efficient extraction, avoids water and solvent consumption, less

contamination, lesser processes and allows substantial energy savings. The results showed

that by using this solvent free extraction technique, the essential oil produced is lighter in

color, higher yield, contains cleaner and distinguishable peaks in GC representing better


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purity and produced a stronger aroma compared to the essential oil produced from hydro

distillation.

Phakawat Tongnuanchan et al. 2014. reviewed on Essential Oils: Extraction, Bioactivities,

and Their Uses for Food Preservation. Essential oils are concentrated liquids of complex

mixtures of volatile compounds and can be extracted from several plant organs. Essential oils

are a good source of several bioactive compounds, which possess antioxidative and

antimicrobial properties. In addition, some essential oils have been used as medicine.

Furthermore, the uses of essential oils have received increasing attention as the natural

additives for the shelf-life extension of food products, due to the risk in using synthetic

preservatives. Essential oils can be incorporated into packaging, in which they can provide

multifunctions termed “active or smart packaging.” Those essential oils are able to modify

the matrix of packaging materials, thereby rendering the improved properties. This review

covers up-to-date literatures on essential oils including sources, chemical composition,

extraction methods, bioactivities, and their applications, particularly with the emphasis on

preservation and the shelf-life extension of food products.

Sources of natural essential oils

Essential Oils are derived from various parts of Plants:[15]

Leaves

Basil Bay leaf Cinnamon

Eucalyptus Lemon grass Melaleuca


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Oregano Patchouli Peppermint

Pines Rosemary Spearmint

Tea tree Wintergreen Thyme

Flowers

Chamomile Clary sage Clove

Geranium Hyssop Jasmine


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Lavender Manuka Marjoram

Rose Ylang – Ylang

Peel

Bergamot Grape fruit Lemon

Orange Tangerine


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Seeds

Almond Anise Celery

Cumin Nutmeg

Wood

Camphor Cedar Rosewood

Sandalwood


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Berries

Allspice Juniper

Barks

Cassia Cinnamon

Resins

Frankincense Myrrh


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Rhizomes

Ginger Calamus

Curcuma

Roots

Valerian Angelica

Vetiver


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Pharmacological Properties of Essential Oils

Antiseptics

Essential oils have antiseptic properties and are active against a wide range of bacteria as well

as on antibio-resistant strains. Moreover, they are also known to be active against fungi and

yeasts (Candida).The most common sources of essential oils used as antiseptics are:

Cinnamon, Thyme; Clover; Eucalyptus; Culin savory; Lavender. Citral, geraniol, linalool and

thymol are much more potent than phenol.[1]

Expectorants and diuretics

When used externally, essential oils like (L‟essence de terebenthine) increase

microcirculation and provide a slight local anaesthetic action. Till now, essential oils are used

in a number of ointments, cream and gels, whereby they are known to be very effective in

relieving sprains and other articular pains. Oral administration of essential oils like

eucalyptus or pin oils, stimulate ciliated epithelial cells to secrete mucus. On the renal

system, these are known to increase vasodilation and in consequence bring about a diuretic

effect.[1]

Spasmolytic and sedative

Essential oils from the Umbellifereae family, Mentha species and verbena are reputed to

decrease or eliminate gastrointestinal spasms. These essential oils increase secretion of

gastric juices. In other cases, they are known to be effective against insomnia.[1]

Others

Cholagogue; anti-inflammatory; cicatrizing.

Chemical Constituents of Essential Oils

Pure essential oils are mixtures of more than 200 components, normally mixtures of terpenes

or phenylpropanic derivatives, in which the chemical and structural differences between

compounds are minimal. They can be essentially classified into two groups:

Volatile fraction: Essential oil constituting of 90–95% of the oil in weight, containing the

monoterpene and sesquiterpene hydrocarbons, as well as their oxygenated derivatives along

with aliphatic aldehydes, alcohols and esters.


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Nonvolatile residue: that comprises 1–10% of the oil, containing hydrocarbons, fatty acids,

sterols, carotenoids, waxes and flavonoids.[14]

1. Hydrocarbons

Essential Oils consist of Chemical Compounds that have hydrogen and carbon as their

building blocks. Basic Hydrocarbon found in plants is isoprene having the following

structure.

(Isoprene)

2. Terpenes

Generally have names ending in “ene.”

For examples: Limonene, Pinene, Piperene, Camphene, etc. Terpenes are anti-inflammatory,

antiseptic, antiviral, and bactericidal. Terpenes can be further categorized in monoterpenes,

sesquiterpenes and diterpenes. Referring back to isoprene units under the Hydrocarbon

heading, when two of these isoprene units join head to tail, the result is a monoterpene, when

three join, it‟s a sesquiterpene and four linked isoprene units are diterpenes.[14]

2.a. Monoterpenes [C10

H16

]

Properties: Analgesic, Bactericidal, Expectorant and Stimulant.

Monoterpenes are naturally occurring compounds, the majority being unsaturated

hydrocarbons (C10

). But some of their oxygenated derivatives such as alcohols, Ketones and

carboxylic acids known as monoterpenoids.

(Limonene) (Menthol)


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The branched-chain C10

hydrocarbons comprises of two isoprene units and is widely

distributed in nature with more than 400 naturally occurring monoterpenes identified.

Moreover, besides being linear derivatives (Geraniol, Citronellol), the monoterpenes can be

cyclic molecules (Menthol – Monocyclic; Camphor – bicyclic; Pinenes (α and β) – Pine

genera as well. Thujone (a monoterpene) is the toxic agent found in Artemisia absinthium

(wormwood) from which the liqueur, absinthe, is made. Borneol and camphor are two

common monoterpenes. Borneol, derived from pine oil, is used as a disinfectant and

deodorant. Camphor is used as a counterirritant, anesthetic, expectorant, and antipruritic,

among many other uses.[14]

Example

Camphene and pinene in cypress oil.

Camphene, pinene and thujhene in black pepper.

2.b. Sesquiterpenes

Properties: anti-inflammatory, anti-septic, analgesic, anti-allergic.

Sesquiterpenes are biogenetically derived from farensyl pyrophosphate and in structure may

be linear, monocyclic or bicyclic. They constitute a very large group of secondary

metabolites, some having been shown to be stress compounds formed as a result of disease or

injury. Sesquiterpene Lactones:

Over 500 compounds of this group are known; they are particularly characteristics of the

Composite but do occur sporadically in other families. Not only have they proved to be of

interest from chemical and chemotaxonomic viewpoints, but also possess many antitumor,

anti-leukemia, cytotoxic and antimicrobial activities. They can be responsible for skin

allergies in humans and they can also act as insect feeding deterrents. Chemically the

compounds can be classified according to their carboxylic skeletons; thus, from the

germacranolides can be derived the guaianolides, pseudoguaianolides, eudesmanolides,

eremophilanolides, xanthanolides, etc.[14]


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A structural feature of all these compounds, which appears to be associated with much of the

biological activity, is the α, β -unsaturated- γ- lactones.

Example

Farnesene in chamomile and lavender.

Beta-caryophyllene in basil and black pepper.

2.c. Diterpenes

Properties: anti-fungal, expectorant, hormonal balancers, hypotensive.

Diterpenes are made of up four isoprene units. This molecule is too heavy to allow for

evaporation with steam in the distillation process, so is rarely found in distilled essential oils.

Diterpenes occur in all plant families and consist of compounds having a C20 skeleton. There

are about 2500 known diterpenes that belong to 20 major structural types. Plant hormones

Gibberellins and phytol occurring as a side chain on chlorophyll are diterpenic derivatives.

The biosynthesis occurs in plastids and interestingly mixtures of monoterpenes and

diterpenes are the major constituents of plant resins. In a similar manner to monoterpenes,

diterpenes arise from metabolism of geranyl geranyl pyrophosphate (GGPP).

Diterpenes have limited therapeutical importance and are used in certain sedatives (coughs)

as well as in antispasmodics and antoxiolytics.[14]


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Example

Sclareol in clary sage is an example of a diterpene alcohol.

3. Alcohols

Properties: anti-septic, anti-viral, bactericidal and germicidal.

Alcohols are the compounds which contains Hydroxyl compounds. Alcohols exist naturally,

either as a free compound, or combined with a terpenes or ester. When terpenes are attached

to an oxygen atom, and hydrogen atom, the result is an alcohol. When the terpene is

monoterpene, the resulting alcohol is called a monoterpenol. Alcohols have a very low or

totally absent toxic reaction in the body or on the skin. Therefore, they are considered safe to

use.[16]

Example

Linalool found in ylang-ylang and lavender.

Geraniol in geranium and rose.

Nerol in neroli.

4. Aldehydes

Properties: anti-fungal, anti-inflammatory, anti-septic, anti-viral, bactericidal, disinfectant,

sedative.

Medicinally, essential oils containing aldehydes are effective in treating Candida and other

fungal infections.

Example

Citral in lemon.

5. Acids

Properties: anti-inflammatory.

Organic acids in their free state are generally found in very small quantities within Essential

oils. Plant acids act as components or buffer systems to control acidity.[15]

Example

Cinnamic and benzoic acid in benzoin.

Citric and lactic.


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6. Esters

Esters are formed through the reaction of alcohols with acids. Essential oils containing esters

are used for their soothing, balancing effects. Because of the presence of alcohol, they are

effective antimicrobial agents. Medicinally, esters are characterized as antifungal and

sedative, with a balancing action on the nervous system. They generally are free from

precautions with the exception of methyl salicylate found in birch and wintergreen which is

toxic within the system.[14]

Example

Linlyl acetate in bergamot and lavender.

Geranyl formate in geranium.

7. Ketones

Properties: anti-catarrhal, cell proliferant, expectorant, vulnery.

Ketones often are found in plants that are used for upper respiratory complaints. They assist

the flow of mucus and ease congestion. Essential oils containing ketones are beneficial for

promoting wound healing and encouraging the formation of scar tissue. Ketones are usually

(not always) very toxic. The most toxic ketone is Thujone found in mugwort, sage, tansy,

thuja and wormwood oils. Other toxic ketones found in essential oils are pulegone in

pennyroyal, and pinocamphone in hyssops. Some non-toxic ketones are jasmone in jasmine

oil, fenchone in fennel oil, carvone in spearmint and dill oil and menthone in peppermint

oil.[12]

Example

fenchone in fennel, carvone in spearmint and dill

Menthone in peppermint.

8. Lactones

Properties: anti-inflammatory, antiphlogistic, expectorant, febrifuge.

Lactones are known to be particularly effective for their anti-inflammatory action, possibly

by their role in the reduction of prostaglandin synthesis and expectorant actions. Lactones

have an even stronger expectorant action then ketones.


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Methods of Extracting Essential Oils

Extraction, as the term is used pharmaceutically, involves the separation of medicinally active

portions of plant or animal tissues from the inactive or inert components by using selective

solvents in standard extraction procedures. The products so obtained from plants are

relatively impure liquids, semisolids or powders intended only for oral or external use. These

include classes of preparations known as decoctions, infusions, fluid extracts, tinctures,

pilular (semisolid) extracts and powdered extracts.[16]

General Methods of Extraction of Essential Oils

1. Hydrodistillation

Hydro distillation is used in the manufacture and extraction of essential oil. This is the

simplest and usually the cheapest process of distillation. Hydro distillation seems to work

best for powders and very tough materials like roots, wood, or nuts. The main advantages of

this method are that less steam is used, shorter processing time and a higher oil yield. In

distillation, the plant material is heated, either by placing it in water which is brought to the

boil or by passing steam through it. The heat and steam cause the cell structure of the plant

material to burst and break down, thus freeing the essential oils. The essential oil molecules

and steam are carried along a pipe and channeled through a cooling tank, where they return to

the liquid form and are collected in a vat. The emerging liquid is a mixture of oil and water,

and since essential oils are not water soluble they can be easily separated from the water and

siphoned off. Essential oils which are lighter than water will float on the surface.[14]

The schematic subsidize apparatus for hydrodistillation.

Mechanism of Distillation

Hydrodistillation of plant material involves the following main physicochemical processes:

i) Hydrodiffusion


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ii) Hydrolysis

iii) Decomposition by heat

Three Types of Hydrodistillation

Three are three types of hydrodistillation for isolating essential oils from plant materials:

1. Water distillation

2. Water and steam distillation

3. Direct steam distillation

Water Distillation

In this method, the material is completely immersed in water, which is boiled by applying

heat by direct fire, steam jacket, closed steam jacket, closed steam coil or open steam coil.

The main characteristic of this process is that there is direct contact between boiling water

and plant material.[17]

Advantages

It permits processing of finely powdered material or plant parts that, by contact with live

steam, would otherwise form lumps through which the steam cannot penetrate.

The stills are inexpensive, easy to construct and suitable for field operation.


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Disadvantages

complete extraction is not possible.

requires a greater number of stills, more space and more fuel.

Water distillation is a slower process than either water and steam distillation or direct

steam distillation.

Water and Steam Distillation

In water and steam distillation, the steam can be generated either in a satellite boiler or within

the still, although separated from the plant material. Like water distillation, water and steam

distillation is widely used in rural areas. Moreover, it does not require a great deal more

capital expenditure than water distillation. Also, the equipment used is generally similar to

that used in water distillation, but the plant material is supported above the boiling water on a

perforated grid. In fact, it is common that persons performing water distillation eventually

progress to water and steam distillation.[17]

Advantages of Water and Steam Distillation

Higher oil yield.

Components of the volatile oil are less susceptible to hydrolysis and polymerization.

Oil quality produced by steam and water distillation is more reproducible.

Disadvantages of Water and Steam Distillation

Due to the low pressure of rising steam, oils of high-boiling range require a greater

quantity of steam for vaporization -hence longer hours of distillation.


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The plant material becomes wet, which slows down distillation as the steam has to

vaporize the water to allow it to condense further up the still.

Direct Steam Distillation

As the name suggests, direct steam distillation is the process of distilling plant material with

steam generated outside the still in a satellite steam generator generally referred to as a boiler.

As in water and steam distillation, the plant material is supported on a perforated grid above

the steam inlet. A real advantage of satellite steam generation is that the amount of steam can

be readily controlled. Because steam is generated in a satellite boiler, the plant material is

heated no higher than 100° C and, consequently, it should not undergo thermal degradation.

Steam distillation is the most widely accepted process for the production of essential oils on

large scale.[19]

Advantages of Direct Steam Distillation

Amount of steam can be readily controlled.

No thermal decomposition of oil constituents.

Most widely accepted process for large-scale oil production, superior to the other two

processes.

Disadvantage of Direct Steam Distillation

Much higher capital expenditure needed to establish this activity than for the other two

processes.[19]

Essential Oil Extraction by Hydrolytic Maceration Distillation

Certain plant materials require maceration in warm water before they release their essential

oils, as their volatile components are glycosidically bound. For example, leaves of


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wintergreen (Gaultheria procumbens) contain the precursor gaultherin and the enzyme

primeverosidase; when the leaves are macerated in warm water, the enzyme acts on the

gaultherin and liberates free methyl salicylate and primeverose. Other similar examples

include brown mustard (sinigrin), bitter almonds (amygdalin) and garlic (alliin).[18]

Essential Oil Extraction by Expression

Expression or cold pressing, as it is also known, is only used in the production of citrus oils.

The term expression refers to any physical process in which the essential oil glands in the

peel are crushed or broken to release the oil. One method that was practiced many years ago,

particularly in Sicily (spugna method), commenced with halving the citrus fruit followed by

pulp removal with the aid of sharpened spoon-knife (known as a rastrello).[15]

The oil was

removed from the peel either by pressing the peel against a hard object of baked clay

(concolina) which was placed under a large natural sponge or by bending the peel into the

sponge. The oil emulsion absorbed by the sponge was removed by squeezing it into the

concolina or some other container. It is reported that oil produced this way contains more of

the fruit odor character than oil produced by any other method.[16]

A second method known as equaling (or the scodella method), uses a shallow bowl of copper

(or sometimes brass) with a hollow central tube; the equaling tool is similar in shape to

ashallow funnel. The bowl is equipped with brass points with blunt ends across which the

whole citrus fruit is rolled by hand with some pressure until all of the oil glands have burst.

The oil andaqueous cell contents are allowed to dribble down the hollow tube into a container

from which the oil is separated by decantation.[17]

Pelatrice Process

In the pelatrice process, citrus fruits are fed from a hopper into the abrasive shell of the

machine. The fruits are rotated against the abrasive shell by a slow-moving Archimedian

screw whose surface rasps the fruit surfaces causing some of the essential oil cavities on the

peel to burst and release their oil-water emulsion. This screw further transports the fruit into a

hopper in which rollers covered with abrasive spikes burst the remaining oil cavities. The oil

and water emulsion is washed away from the fruit by a fine spray of water. The emulsion

next passes through a separator where any solids are removed, after which it passes through

two centrifugal separators working in series to yield the pure oil. Most bergamot oil and some

lemon oil are produced this way in Italy.[15]


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“Pelatrice” for the extraction of citrus essential oil

Sfumatrice Process

The sfumatrice equipment consists of a metallic chain that is drawn by two horizontal ribbed

rollers. The peels are conveyed through these rollers during which time they are pressed and

bent to release their oil. As in pelatrice, the oil is washed away from the sfumatrice rollers by

fi ne sprays of water. Again, the oil is initially passed through a separator prior to being sent

to two centrifuges in series, so that purified oil can be produced. At one time, sfumatrice was

the most popular process for citrus oil isolation in Italy; however, today the pelatrice method

appears more popular.[17]

Essential Oil Extraction with Cold Fat (Enfleurage)

Enfleurage is a process that uses odorless fats that are solid at room temperature to capture

the fragrant compounds exuded by plants. The process can be "cold" enfleurage or "hot"

enfleurage.[5]


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There are two types of processes

In cold enfleurage, a large framed plate of glass, called a chassis, is smeared with a layer

of animal fat, usually lard or tallow (from pork or beef, respectively) and allowed to set.

Botanical matter, usually petals or whole flowers, is then placed on the fat and its scent is

allowed to diffuse into the fat over the course of 1-3 days. The process is then repeated by

replacing the spent botanicals with fresh ones until the fat has reached a desired degree of

fragrance saturation. This procedure was developed in southern France in the 18th

century for the production of high-grade concentrates.

In hot enfleurage, solid fats are heated and botanical matter is stirred into the fat. Spent

botanicals are repeatedly strained from the fat and replaced with fresh material until the

fat is saturated with fragrance. This method is considered the oldest known procedure for

preserving plant fragrance substances.[5]

Modern (Non-traditional) Methods of Extraction of Essential Oils

Traditional methods of extraction of essential oils have been discussed and these are the

methods most widely used on commercial scale. However, with technological advancement,

new techniques have been developed which may not necessarily be widely used for

commercial production of essential oils but are considered valuable in certain situations, such

as the production of costly essential oils in a natural state without any alteration of their

thermosensitive components or the extraction of essential oils for micro-analysis. These

techniques are as follows:[15]


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Headspace trapping techniques

Static headspace technique

Vacuum headspace technique

Dynamic headspace technique

Solid phase micro-extraction (SPME)

Supercritical fluid extraction (SFE)

Phytosol (phytol) extraction

Protoplast technique

Simultaneous distillation extraction (SDE)

Microwave distillation

Controlled instantaneous decomposition (CID)

Thermomicrodistillation

Microdistillation

Molecular spinning band distillation

Membrane extraction

Encapsulation of Essential oils

Essential oils are natural products which have many interesting applications. Extraction of

essential oils from plants is performed by classical and innovative methods. Numerous

encapsulation processes have been developed and reported in the literature in order to

encapsulate biomolecules, active molecules, nanocrystals, oils and also essential oils for

various applications such as in vitro diagnosis, therapy, cosmetic, textile, food etc. Essential

oils encapsulation led to numerous new formulations with new applications. This insures the

protection of the fragile oil and controlled release. The most commonly prepared carriers are

polymer particles, liposomes and solid lipid nanoparticles.[21]


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Reason for Encapsulation

The reasons for microencapsulation are countless. It is mainly used to increase the stability

and life of the product being encapsulated, facilitate the manipulation of the product and

control its liberation in an adequate time and space. In some cases, the core must be isolated

from its surroundings, as in isolating vitamins from the deteriorating effects of oxygen,

retarding evaporation of a volatile core, improving the handling properties of a sticky

material, or isolating a reactive core from chemical attack. In other cases, the objective is not

to isolate the core completely but to control the rate at which it leaves the microcapsule, as in

the controlled release of drugs or pesticides. The problem may be as simple as masking the

taste or odor of the core, or as complex as increasing the selectivity of

an adsorption or extraction process. In environmental science, a pesticide may be

microencapsulated to minimize leaching or volatilization risks.[22]

Techniques of Encapsulation

Physical methods

Pan coating

The pan coating process, widely used in the pharmaceutical industry, is among the oldest

industrial procedures for forming small, coated particles or tablets. The particles are tumbled

in a pan or other device while the coating material is applied slowly.[21]

Air-suspension coating

Air-suspension coating gives improved control and flexibility compared to pan coating. In

this process the particulate core material, which is solid, is dispersed into the supporting air

stream and these suspended particles are coated with polymers in a volatile solvent leaving a

very thin layer of polymer on them. This process is repeated several hundred times until the

required parameters such as coating thickness, etc., are achieved.[21]

Centrifugal extrusion

Liquids are encapsulated using a rotating extrusion head containing concentric nozzles. In

this process, a jet of core liquid is surrounded by a sheath of wall solution or melt. As the jet

moves through the air it breaks, owing to Rayleigh instability, into droplets of core, each

coated with the wall solution. While the droplets are in flight, the molten wall may be

hardened or a solvent may be evaporated from the wall solution.[22]


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Vibrational nozzle

Core-shell encapsulation or microgranulation (matrix-encapsulation) can be done using a

laminar flow through a nozzle and an additional vibration of the nozzle or the liquid. The

vibration has to be done in resonance with the Rayleigh instability and leads to very uniform

droplets. The liquid can consist of any liquids with limited viscosities e.g. solutions,

emulsions, suspensions, melt etc. The soldification can be done according to the used gelation

system with an internal gelation (e.g. sol-gel processing, melt) or an external (additional

binder system, e.g. in a slurry).[21]

Spray–drying

Spray drying serves as a microencapsulation technique when an active material is dissolved

or suspended in a melt or polymer solution and becomes trapped in the dried particle. The

main advantages are the ability to handle labile materials because of the short contact time in

the dryer and the operation is economical. In modern spray dryers the viscosity of the

solutions to be sprayed can be as high as 300 mPa·s. Applying this technique, along with the

use of supercritical carbon dioxide, sensitive materials like proteins can be encapsulated.[22]

Physicochemical methods

Ionotropic gelation

Ionotropic gelation occurs when units of uric acid in the chains of the polymer alginate,

crosslink with multivalent cations. These may include, calcium, zinc, iron and aluminium.[22]

Coacervation-phase separation

Coacervation-phase separation consists of three steps carried out under continuous agitation.

1. Formation of three immiscible chemical phases: liquid manufacturing vehicle phase, core

material phase and coating material phase.

2. Deposition of coating: core material is dispersed in the coating polymer solution. Coating

polymer material coated around core. Deposition of liquid polymer coating around core

by polymer adsorbed at the interface formed between core material and vehicle phase.

3. Rigidization of coating: coating material is immiscible in vehicle phase and is made rigid.

This is done by thermal, cross-linking, or dissolution techniques.[21]


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Chemical methods

Interfacial polycondensation

In interfacial polycondensation, the two reactants in a polycondensation meet at an interface

and react rapidly. The basis of this method is the classical Schotten-Baumann

reaction between an acid chloride and a compound containing an active hydrogen atom, such

as an amine or alcohol, polyesters, polyurea, polyurethane.[21]

Interfacial cross-linking

Interfacial cross-linking is derived from interfacial polycondensation, and was developed to

avoid the use of toxic diamines, for pharmaceutical or cosmetic applications. In this method,

the small bifunctional monomer containing active hydrogen atoms is replaced by a

biosourced polymer, like a protein. When the reaction is performed at the interface of an

emulsion, the acid chloride reacts with the various functional groups of the protein, leading to

the formation of a membrane.[22]

In situ polymerization

In a few microencapsulation processes, the direct polymerization of a single monomer is

carried out on the particle surface. In one process, e.g. cellulose fibers are encapsulated

in polyethylene while immersed in dry toluene. Usual deposition rates are about 0.5μm/min.

Coating thickness ranges 0.2–75 µm (0.0079–2.9528 mils). The coating is uniform, even over

sharp projections. Protein microcapsules are biocompatible and biodegradable and the

presence of the protein backbone renders the membrane more resistant and elastic than those

obtained by interfacial polycondensation.[21]

Matrix polymerization

In a number of processes, a core material is imbedded in a polymeric matrix during formation

of the particles. A simple method of this type is spray-drying, in which the particle is formed

by evaporation of the solvent from the matrix material. However, the solidification of the

matrix also can be caused by a chemical change.[21]

CONCLUSION

Some of the major constraints in sustainable industrial exploitation of medicinal and aromatic

plants (MAPs) are due to the fact that the countries of South East Asia have poor agricultural

practices for MAPs, unscientific and indiscriminate gathering practices from the wild, poor

postharvest and post-gathering practices leading to poor quality raw material, lack of research


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for the development of high-yielding varieties of MAPs, poor propagation methods,

inefficient processing techniques, poor quality control procedures, lack of research on process

and product development, difficulty in marketing, non-availability of trained personnel, lack

of facilities and tools to fabricate equipment locally, and finally lack of access to the latest

technologies and market information. This calls for co-operation and coordination among

various institutes and organizations of the region, in order to develop MAPs for sustainable

commercial exploitation.

The process of extracting MAPs determines how efficiently we add value to MAP

bioresources. In the case of essential oils, the extraction process affects the physical as well

as internal composition. External appearance, at times, can result in rejection of the batch

even if the analytical results are within acceptable limits. Furthermore, essential oils are

evaluated internationally for their olfactory properties by experienced perfumers and these

olfactory qualities supersede analytical results. Variations in the chemical constituents of the

extracts of medicinal plants may result by using non-standardized procedures of extraction.

Efforts should be made to produce batches with quality as consistent as possible (within the

narrowest possible range).

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