Essential Oils: Sources, Production and Applications 9783110791594

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Rajendra Chandra Padalia, Dakeshwar Kumar Verma, Charu Arora and Pramod Kumar Mahish (Eds.) Essential Oils

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Essential Oils

Sources, Production and Applications Edited by Rajendra Chandra Padalia, Dakeshwar Kumar Verma, Charu Arora and Pramod Kumar Mahish

Editors Dr. Rajendra Chandra Padalia CSIR-Central Institute of Medicinal and Aromatic Plants (CIMAP) Pantnagar 263 149 Uttarakhand India Email: [email protected] Dr. Charu Arora Department of Chemistry Ghasidas University Bilaspur Chhattisgarh 495009 India Email: [email protected]

Dakeshwar Kumar Verma, Ph.D. Department of Chemistry Govt. Digvijay Autonomous Postgraduate College Rajnandgaon 491441 Chhattisgarh India Email: [email protected] Dr. Pramod Kumar Mahish Department of Biotechnology Govt. Digvijay Autonomous Postgraduate College Rajnandgaon 491441 Chhattisgarh India Email: [email protected]

ISBN 978-3-11-079159-4 e-ISBN (PDF) 978-3-11-079160-0 e-ISBN (EPUB) 978-3-11-079161-7 Library of Congress Control Number: 2022947370 Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the internet at http://dnb.dnb.de. © 2023 Walter de Gruyter GmbH, Berlin/Boston Cover image: egal/iStock/Getty Images Plus Typesetting: Integra Software Services Pvt. Ltd. Printing and binding: CPI books GmbH, Leck www.degruyter.com

Contents Author list

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Meenakshi Sharma, Dipti Bharti, Vatsala Soni, Vaishali Soni and Charu Arora Chapter 1 Introduction and general properties of essential oils 1 Sushma Kholiya, Amit Chauhan, Dipender Kumar, Venkatesha KT, R. K. Upadhyay and R. C. Padalia Chapter 2 Essential oils, applications, and different extraction methods 25 Shekhar Verma, Sonam Soni, Nagendra Chandrawanshi and Shivendra Singh Dewhare Chapter 3 Sources and raw materials of essential oils 47 R Rushendran, Anuragh Singh, Kumar B Siva and K Ilango Chapter 4 Chemical composition of essential oils – fatty acids 65 Saeed Mollaei, Poopak Farnia and Saeid Hazrati Chapter 5 Essential oils and their constituents 89 Shivendra Singh Dewhare, Nagendra Kumar Chandrawanshi, Shekhar Verma, Sonam Soni and Pramod Kumar Mahish Chapter 6 Extraction, production, and encapsulation of essential oils 121 Nagendra Kumar Chandrawanshi, Deepali, Anjali Kosre, Shivendra Singh Dewhare, Shekhar Verma, Pramod Kumar Mahish and Ashish Kumar Chapter 7 Bioactivity of essential oils – anticancer, anti-HIV, antiparasitic, anti-inflammatory, and other activities 133

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Contents

V. Shanthi and Shubha Diwan Chapter 8 Application of essential oils in industries and daily usage Joshua H. Santos and Mark Lloyd G. Dapar Chapter 9 Application of essential oils in pharmaceutical industry Siham Abdulrazzaq Salim Chapter 10 Application of essential oils in agriculture and veterinary

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Deepali Koreti, Anjali Kosre, Pramod Kumar Mahish, Nagendra Kumar Chandrawanshi and Shri Ram Kunjam Chapter 11 Application of essential oils in alternative medicine 237 Vatsala Soni, Dipti Bharti, Meenakshi Bharadwaj, Vaishali Soni, Richa Saxena and Charu Arora Chapter 12 Toxicity of essential oils 253 Himanshu Pandey, Sushma Kholiya, RC Padalia, Priyanka Tiwari and Ameeta Tiwari Chapter 13 Essential oil screening and bioactive potential of some selected trees from temperate zone of Kumaun Himalaya Uttarakhand 269 Index

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Author list Sushma Kholiya CSIR-Central Institute of Medicinal and Aromatic Plants (CIMAP) Research Centre Pantnagar 263 149 Uttarakhand India Amit Chauhan CSIR-Central Institute of Medicinal and Aromatic Plants (CIMAP) Research Centre Pantnagar 263149 Uttarakhand India Dipender Kumar CSIR-Central Institute of Medicinal and Aromatic Plants (CIMAP) Research Centre Pantnagar 263 149 Uttarakhand India Venkatesha KT CSIR-Central Institute of Medicinal and Aromatic Plants (CIMAP) Research Centre Pantnagar 263 149 Uttarakhand India R. K. Upadhyay CSIR-Central Institute of Medicinal and Aromatic Plants (CIMAP) Research Centre Pantnagar 263 149 Uttarakhand India R. C. Padalia CSIR-Central Institute of Medicinal and Aromatic Plants (CIMAP) Research Centre Pantnagar 263 149 Uttarakhand India and https://doi.org/10.1515/9783110791600-203

Academy of Scientific and Innovative Research (AcSIR) CSIR-Human Resource Development Centre (CSIR-HRDC) Postal Staff College Area Sector 19, Kamla Nehru Nagar Ghaziabad 201 002 Uttar Pradesh India E-mail: [email protected] Saeed Mollaei Phytochemical Laboratory Department of Chemistry Faculty of Sciences Azarbaijan Shahid Madani University Tabriz Iran E-mail: [email protected] Poopak Farnia Mycobacteriology Research Centre (MRC) National Research Institute of Tuberculosis and Lung Disease (NRITLD) Shahid Beheshti University of Medical Sciences Tehran Iran Saeid Hazrati Department of Agronomy Faculty of Agriculture Azarbaijan Shahid Madani University Tabriz Iran E-mail: [email protected] Joshua H. Santos Chemicals and Energy Division Department of Science and Technology – Industrial Technology Development Institute DOST Compound General Santos Avenue Bicutan Taguig, Metro Manila Philippines Email: [email protected]

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Author list

Mark Lloyd G. Dapar Department of Biology College of Arts and Sciences and Center for Biodiversity Research and Extension in Mindanao and Microtechnique and Systematics Laboratory Natural Science Research Center Central Mindanao University University Town Musuan Bukidnon 8714 Philippines Email: [email protected] Shekhar Verma University College of Pharmacy Raipur Pandit Deendayal Upadhyay Memorial Health Sciences and Ayush University of Chhattisgarh Chhattisgarh 493661 India Email: [email protected] Sonam Soni University College of Pharmacy Raipur Pandit Deendayal Upadhyay Memorial Health Sciences and Ayush University of Chhattisgarh Chhattisgarh 493661 India Nagendra Chandrawanshi School of Studies in Biotechnology Pandit Ravishankar Shukla University Raipur Chhattisgarh India Shivendra Singh Dewhare School of Studies in Life Science Pandit Ravishankar Shukla University Raipur Chhattisgarh India

Rushendran R Department of Pharmacology SRM College of Pharmacy SRM Institute of Science and Technology Kattankulathur 603 203 Chengalpattu Tamil Nadu India Anuragh Singh Department of Pharmacology SRM College of Pharmacy SRM Institute of Science and Technology Kattankulathur 603 203 Chengalpattu Tamil Nadu India Siva Kumar B Department of Pharmaceutical Chemistry SRM College of Pharmacy SRM Institute of Science and Technology Kattankulathur 603 203 Chengalpattu Tamil Nadu India Ilango K Department of Pharmaceutical Quality Assurance SRM College of Pharmacy SRM Institute of Science and Technology Kattankulathur 603 203 Chengalpattu Tamil Nadu India Email: [email protected] Shivendra Singh Dewhare School of Studies in Life Science Pt. Ravishankar Shukla University Raipur Chhattisgarh India Email: [email protected]

Author list

Nagendra Kumar Chandrawanshi School of Studies in Biotechnology Pt. Ravishankar Shukla University Raipur Chhattisgarh India

Anjali Kosre School of Studies in Biotechnology Pt. Ravishankar Shukla University Raipur Chhattisgarh India

Shekhar Verma University College of Pharmacy Pt. Deendayal Upadhyay Memorial Health Sciences and Ayush University of Chhattisgarh Chhattisgarh India

Shivendra Singh Dewhare School of Studies in Life Science Pt. Ravishankar Shukla University Raipur Chhattisgarh

Sonam Soni University College of Pharmacy Pt. Deendayal Upadhyay Memorial Health Sciences and Ayush University of Chhattisgarh Chhattisgarh India Pramod Kumar Mahish Government Digvijay Autonomous Post Graduate College Rajnandgaon Chhattisgarh India Nagendra Kumar Chandrawanshi School of Studies in Biotechnology Pt. Ravishankar Shukla University Raipur Chhattisgarh India E mail: [email protected] Deepali School of Studies in Biotechnology Pt. Ravishankar Shukla University Raipur Chhattisgarh India

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Shekhar Verma University College of Pharmacy Pandit Deendayal Upadhyay Memorial Health Sciences and Ayush University of Chhattisgarh Chhattisgarh India Pramod Kumar Mahish Government Digvijay Autonomous Post Graduate College Rajnandgaon Chhattisgarh India Ashish Kumar Department of Biotechnology Sant Gahira Guru University Sarguja Ambikapur Chhattisgarh India V. Shanthi Department of Microbiology and Biotechnology St. Thomas College Bhilai Chhattisgarh India

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Author list

Shubha Diwan Department of Microbiology and Biotechnology St. Thomas College Bhilai Chhattisgarh India E-mail: [email protected] Siham Abdulrazzaq Salim Department of Biology College of Education Al-Iraqia University Baghdad Iraq Deepali Koreti School of Studies in Biotechnology Pt. Ravishankar Shukla University Raipur Chhattisgarh India Email: [email protected] Anjali Kosre School of Studies in Biotechnology Pt. Ravishankar Shukla University Raipur Chhattisgarh India Pramod Kumar Mahish Government V.Y.T. PG Autonomous College Durg Chhattisgarh India Nagendra Kumar Chandrawanshi School of Studies in Biotechnology Pt. Ravishankar Shukla University Raipur Chhattisgarh India Shri Ram Kunjam Government Digvijay (Autonomous) Post Graduate College Rajnandgaon Chhattisgarh India

Vatsala Soni PEC-Punjab Engineering College Chandigarh 160012 India Dipti Bharti Department of Applied Sciences and Humanities Darbhanga College of Engineering Darbhanga 846005 Bihar India Meenakshi Bharadwaj Department of Chemistry IEC University Baddi Himachal Pradesh India Vaishali Soni PGIMER-Post Graduate Government Institute of Medical Education and Research Chandigarh 160012 India Richa Saxena Department of Biotechnology Invertis University Bareilly 243001 Uttar Pradesh India Charu Arora Department of Chemistry Guru Ghasidas University Bilaspur495009 Chhattisgarh India Himanshu Pandey M.B.G.P.G College Haldwani Kumaun University Nainital 263139 Uttarakhand India

Author list

Sushma Kholiya M.B.G.P.G College Kumaun University Haldwani Nainital 263139 Uttarakhand India and CSIR-CIMAP Research Center Pantnagar 263149 Uttarakhand India R. C. Padalia CSIR-CIMAP Research Center Pantnagar 263149 Uttarakhand India Priyanka Tiwari M.B.G.P.G College Kumaun University Haldwani Nainital 263139 Uttarakhand India Ameeta Tiwari M.B.G.P.G College Kumaun University Haldwani Nainital 263139 Uttarakhand India Email: [email protected]

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Meenakshi Sharma IEC University Baddi 174103 Himachal Pradesh India Dipti Bharti Department of Applied Sciences and Humanities Darbhanga College of Engineering Darbhanga Bihar 846005 India Vatsala Soni, PEC-Punjab Engineering College Chandigarh 160012 India Vaishali Soni, PGIMER-Post Graduate Government Institute of Medical Education and Research Chandigarh 160012 India Charu Arora Department of Chemistry Guru Ghasidas University Bilaspur 495009 Chhattisgarh India

Meenakshi Sharma, Dipti Bharti, Vatsala Soni, Vaishali Soni and Charu Arora

Chapter 1 Introduction and general properties of essential oils Abstract: This chapter covers the literature data summarizing, on the one hand, the chemistry of essential oils and, on the other hand, their most important activities. Essential oils, which are complex mixtures of volatile compounds particularly abundant in aromatic plants, are mainly composed of terpenes biogenerated by the mevalonate pathway. These volatile molecules include monoterpenes (hydrocarbon and oxygenated monoterpenes) and also sesquiterpenes (hydrocarbon and oxygenated sesquiterpenes). Furthermore, they contain phenolic compounds, which are derived via the shikimate pathway. Thanks to their chemical composition, essential oils possess numerous biological activities (antioxidant, anti-inflammatory, antimicrobial, etc.) of great interest in food and cosmetic industries, as well as in the human health field. Keywords: Introduction of essential oils, chemical composition, general properties

1.1 Introduction Essential oils are complex mixtures of volatile chemicals found in living organisms. The attraction of medicinal and aromatic plants is continuously growing due to increasing consumers demand and interest in these plants for culinary, medicinal, and other anthropogenic applications [1]. The term “essential oil” dates back to the sixteenth century. Essential oils or “essences” owe their name to their flammability. Numerous authors have attempted to provide a definition for essential oils [2]. “The essential oil is the product obtained from a vegetable raw material, either by steam distillation or by mechanical processes from the epicarp of Citrus, or dry distillation.”

Meenakshi Sharma, IEC University Baddi, Himachal Pradesh 174103, India Dipti Bharti, Department of Applied Science and Humanities, Darbhanga College of Engineering, Darbhanga, Bihar 846005, India Vatsala Soni, Punjab Engineering College, Chandigarh 160012, India Vaishali Soni, PGIMER-Post Graduate Government Institute of Medical Education and Research, Chandigarh 160012, India Charu Arora, Department of Chemistry, Guru Ghasidas Vishwavidyalaya, Bilaspur-495009, C.G https://doi.org/10.1515/9783110791600-001

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Essential oils are widely used in flavor, food, fragrance, and cosmetic industries for various applications. Contact allergy to them is well known and has been described for 80 essential oils. The relevance of positive patch test reactions often remains unknown. Knowledge of the chemical composition of essential oils among dermatologists is suspected to be limited, as such data are published in journals not read by the dermatological community. Therefore, the authors have fully reviewed and published the literature on contact allergy and on the chemical composition of essential oils. These volatile oils are generally liquids and are colorless at room temperature. Essentials oils are insoluble in water but soluble in alcohol, ether, and fixed oils. They have a refractive index and a very high optical activity. They have a characteristic odor, are usually liquids at room temperature, and have a density less than unity, with the exception of a few cases (cinnamon, sassafras, and vetiver). These volatile oils present in herbs are responsible for different scents that plants emit. They are widely used in cosmetics industry, perfumery, and also aromatherapy. The latter is intended as a therapeutic technique including massage, inhalations, or baths using these volatile oils [3]. The last key will serve as chemical signals allowing the plant to control or regulate its environment (ecological role), attraction of pollinating insects, repellent to predators, inhibition of seed germination, or communication between plants (emission signals chemically signaling the presence of herbivores, for example). Moreover, aromatic plants are the major source of essential oils which also possess antifungal or insecticide and deterrent activities. These may be found in almost all parts of aromatic plants that may contain essential oils such as leaves, flowers, bark, seeds, fruits, wood, rhizome, root, and root bark. . Leaves (eucalyptus, cedar, and laurel) . Leafy branches (pine) . Herbaceous parts (oregano, mint, and sage) . Flowers (rose and jasmine) . Dried buds (cloves) . Bark (cinnamon and cassia) . Wood (sandalwood, cedarwood, and rosewood) . Bulb (onion and garlic) . Roots (angelica, vetiver, and orris) . Rhizomes (ginger and acorus) . Fruits (aniseed, fennel, coriander, and cumin) . Fruit peel (orange and lemon) . Pseudofruit (juniper) . Seed (carrot seed, mustard seed, and cardamom) . Root bark (sassafras and xylopia) . Balsam (storax and Peru balsam) . Oleo-gum resin (frankincense, myrrh, and mastic) . Oleoresin (turpentine and opopanax) . Lichen (oak moss and tree moss)

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This chapter describes the mechanism of essential secondary metabolite biosynthesis, essential oil extraction, essential oil chemical profile, and its pharmacological potential against the top list of human killer diseases as presented by the World Health Organization.

1.2 Chemical composition 1.2.1 Biosynthesis Terpenoid and phenylpropanoid derivatives are the main components found in essential oils. In most plants, their essential oils contain terpenoids at around 80%. But the presence of phenylpropanoid derivatives affords the essential oils’ significant flavor, odor, and piquant. Along with substantial improvements in analytical techniques, characteristics such as specific gravity, optical rotation, refractive index, and solubility continue to be important in determining the quality of essential oils and aroma compounds [4]. The secondary metabolites of volatile plants known as essential oils have a molecular mass less than 300 and a nice odor. The essential oils are weakly soluble in water but are soluble in alcohol, nonpolar solvents, waxes, and oils [5, 6]. There are few exceptions to the rule that most essential oils are colorless or pale yellow, such as chamomile (Matricaria chamomilla), and chrysanthemum which produces blue color oil, with the exception of sassafras, vetiver, cinnamon, and clove’s essential oils, which are denser than water. The changes in characteristics such as solubility in ethanol, relative density, refractive index, and optical purity of a particular essential oil indicate the adulteration and modulation in chemical composition [7].

1.3 Essential oil extraction Essential oil extraction is one of the critical points that can affect the chemical profile of the essential oil. Sensu stricto, essential oils are volatile odorant complex mixture obtained by distillation. The extraction of essential oils from plants is one of key processes for their end uses and to improve the yield and quality of essential oil. There are various methods employed for extraction of essential oils, which includes both traditional and modern techniques in many parts of the globe. By using several distillation process techniques, essential oils are separated from aromatic plants. Other volatile isolates, however, are also obtained using solvent extraction, cold press, and various other methods. Numerous techniques, including the most popular ones like hydrodistillation, steam distillation, cohobation, cold pressing, maceration, solvent extraction, and simultaneous distillation–extraction techniques, and supercritical fluid techniques, can be employed for this purpose [8]. Despite the fact that these

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methods have been employed for essential oil extraction for a long time, their use has revealed a wide range of drawbacks, including the loss of some volatile compounds, low extraction efficiency, the degradation of unsaturated or ester compounds through thermal or hydrolytic effects, and potential toxic solvent residues in extracts. The oil extraction companies concentrated on the development of emergent extraction technologies as a result of the rise in energy costs and the advent of the “Green Era.” Several new methods are currently available for the extraction of essential oils from plants, including supercritical fluid extraction, pressurized liquid extraction, pressurized hot water extraction, membrane-assisted solvent extraction, solid-phase microextraction, microwave-assisted extraction, and ultrasound-assisted extraction, in order to overcome the drawbacks of traditional methods of extraction. Most of these extraction methods lead most of the time to artifactual products as well as transformed products. To better understand, the following sections will present the most used methods and their principal limits in the way of modification of the original chemical profile of essential oils [9–11].

1.3.1 Distillation method Distillation methods are a group of methods using steam as a compound vector or transporter. In fact, in distillation method, the plant material may be immersed in water or may not, and after heating to water’s boiling point [12], the impression formed in the reactor by steam as well as high temperature will produce the vaporization of these volatile compounds from their stockade cell to the environment of the reactor. The gas is pouched throughout a cooler. The condensation of water and volatilized compounds from their vapor to water phase forms a mixture that can be separated based on their density.

1.3.2 Hydrodistillation In this method, the plant material is completely soaked in water, indicating that the raw materials come into direct contact with hot water [13]. Depending on the quality of the material treated each time, it may float on the water or may totally submerge. The water is heated to the boiling point using any standard method, such as direct flame, steam jacket, closed steam coil, or, in rare instances, a perforated steam coil. Evaporation, condensation, and separation based on difference in essential oil density are same as in other distillation processes. Before conducting any field distillations for large-scale manufacturing, a small-scale water distillation in glassware (Clevenger apparatus for laboratory purpose), which works on the same principle of hydrodistillation, should be carried out to see if any changes occur during the distillation process [14]. This technique is very simple and inexpensive, and with

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simple-to-build units it is suitable for on-field extraction of essential oils. Moreover, this technique is recommended to fine powdered materials of plant parts, mainly spices. This distillation process is treated as an art by local distillers, who rarely try to optimize both oil yield and quality; therefore, it requires a great deal of expertise and procedure knowledge. Other disadvantages of this technique are that some of the oil components like esters are sensitive to hydrolysis, and acyclic monoterpenes, hydrocarbons, and aldehydes are susceptible to polymerize during hydrodistillation. Sometimes the loss in yield and quality of essential oils observed is due to solubility of oxygenated components such as phenols and incomplete vaporization of high-boiling oil components [15–17].

1.3.3 Cold pressing Cold press method, also known as scarification method, is a low-cost technique for extraction of essential oils of certain aromatic plants, especially for extraction of oils from the peels of citrus fruits by applying mechanical pressure in the form of crushing and pressing in low temperature. Different types of cold press machines, namely, gear, rack, hydraulic press, and scrapers used for cold extraction at industrial level. The essential oil extracted from this method also contains certain plant pigments, coumarins, glucosinolate residues, and other volatiles, which are not part of the same essential oil extracted from distillation methods. The cold-pressed essential oils are of higher purity retaining the real aroma of the extraction and fetch premium price in trade [8, 18].

1.3.4 Steam distillation In the process of steam distillation, steam is generated in a satellite steam generator/boiler and then it is driven through a pipe into a still where the plant material is placed on a perforated tray just as in hydro-cum-steam distillation [17]. A significant benefit of satellite steam generation is the ease with which the volume of steam can be controlled. This method is most frequently used for the industrial manufacturing of essential oils on large batches through one satellite boiler. The major advantages of steam distillation are its controlled distillation as steam can be regulated through boiler, no thermal degradation of essential oil constituents, and consistent quality of the extracted essential oils. The only disadvantages are due to its higher capital expenditure and requirement of trained persons for boiler operation. In terms of essential oil yield, distillation speed, and consistent quality of the essential oil, the steam distillation is superior over hydro-cum-steam distillation and hydrodistillation. The most common method for extracting essential oils on a large scale is steam distillation. However, hydro-cum-steam distillation requires very less investment to

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establish the distillation setup as compared to steam distillation, and is therefore the most frequently used distillation process for farmers and budding entrepreneurs. In specifically designed field distillation units, commonly known as improved field distillation units, the inclusion of calandria with smoke pipe inside the still acts as inbuilt small boiler, reduces the fuel consumption, and generates balanced steam for essential oil extraction [15–17].

1.3.5 Solvent extraction Essential oils can also be extracted using organic solvents such as acetone, hexane, petroleum ether, methanol, or ethanol. In this method, the plant material is submerged or macerated with the organic solvent for a certain period. The essential oils along with pigment and few other components become miscible with the used solvents. After filtration, the essential oil’s saturated supernatant was evaporated by spontaneous evaporation or using a rotary evaporator under pressure to the concentrate form known as concrete. The concrete is composed of wax, fragrance, and essential oil. The essential oil is extracted from this concrete by using ethyl alcohol, which is actually known as absolute, wax-free residue; and the essential oils from this absolute are distilled at low temperature under controlled conditions. The main disadvantage of this technique is longer extraction time and quality deterioration due to the presence of solvent trace. This method is useful for delicate flower extraction, which consists of various thermolabile constituents. The concrete and absolutes have their own demands in perfumery industry, subject to meet the regulatory regulation for trace of the solvent [18, 19].

1.3.6 Enfleurage This is one of the traditional methods to extract the fragrant volatile/essential oils of flowers and delicate plant parts. However, the traditional perfumers in some parts of India, France, Egypt, and Indonesia still use this technique for oriental perfumery material. In this method, the flower petals are spread over grease and cold fat (tallow or lard) for a period of time with specially designed chassis, and the essence is absorbed over the fat till absorption saturation. The essential oils/volatiles/ fragrances are then extracted using alcohol. Thereafter, the alcoholic mixture of the essential oil is vacuum distilled to separate the oil from the alcohol. This technique is time-consuming, labor-intensive, and expensive [8].

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1.3.7 Microwave-assisted essential oil extraction Microwave-assisted essential oil extraction is a variant of the distillation method where the heating source has been changed from the normal electric heating cap by the microwave. The advantage here is the hypothetical increase in the extraction yield because the increase in yield is not as spectacular as difficult. It is true that it is better to crush the plant material, but in comparison to the classic distillation method [20], the essential oil yield is systematically the same. The principle of this method is based on the change of the polarity of water by the waves and of course the heating that will play the same role as in classic distillation method. This method has, in addition, the limit of the normal distillation method, the fact that the microwave can lead to chemical stereoswitching from one isomer to another.

1.3.8 Ultrasound-assisted extraction (UAE) The ultrasound-assisted extraction (UAE) technique has been recognized one of the best extraction techniques for various herbal industries. It is also known as ultrasonic extraction or sonication and utilizes ultrasonic energy for the extraction. UAE is used to isolate volatile components from natural materials at room temperature while using organic solvents, which reduces the amount of solvents used, speeds up the extraction process, and increases the extract yield as compared to traditional procedures. This method is well suited for thermolabile and unstable compounds and is more selective when compared to other extraction techniques [21].

1.4 Method for chemical analysis There is a myriad of technique and methods for essential oil chemical profiling. All the methods used in organic chemistry can be used here. Due to their volatility nature, the compounds that constitute essential oil are preferably analyzed by gas chromatography (GC). GC alone does not provide enough data for good chemical proofing. Therefore, many other analytical tools have been used such as mass spectrometry (MS), infrared (IR) spectroscopy, and nuclear magnetic resonance. As well, many techniques have been used to make the GC a better tool for chemical profiling, and these include chiral-selective GC and multidimensional GC. Advances in liquid chromatography have highlighted the usefulness of high-pressure liquid chromatography (HPLC) as a tool for essential oil analysis. Many variants are available to date as multidimensional HPLC, HPLC-MS, and HPLC-GC. GC coupled with MS is used for its popularity, and the Fourier-transform IR spectroscopy is used for its simplicity, for being environment-friendly, and for long-term cost-effectiveness [22].

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1.5 Chemistry of essential oils Essential oils are produced by various differentiated structures, especially the number and characteristics of which are highly variable. Essential oils are localized in the cytoplasm of certain plant cell secretions, which lie in one or more organs of the plant, namely, the secretory hairs or trichomes, epidermal cells, internal secretory cells, and the secretory pockets. These oils are complex mixtures that may contain over 300 different compounds [4]. They consist of organic volatile compounds, generally of low molecular weight (