Essential oils are odorous principles which are stored in special plant cells for example in glands, glandular hairs, oil ducts and resin ducts. They may occur in flowers, fruits, leaves, roots, wood, stems bark and saps. These oils are responsible for the distinctive aromas associated with individual plant species. Essential oils have been shown to possess antibacterial, antifungal, antiviral, insecticidal and antioxidant properties. Some oils have been used in cancer treatment .Some other oils have been used in food preservation, aromatherapy, and fragrance industries .Essential oils are a rich source of biologically active compounds. There has been an increased interest in looking at antimicrobial properties of extracts from aromatic plants particularly essential oils .Therefore, it is reasonable to expect a variety of plant compounds in these oils with specific as well as general antimicrobial activity and antibiotic potential [1].

Antimicrobial Activity of Essential Oils

Plant and plant-derived natural products have a long and significant history in traditional medicine all over the world. Many studies in the recent past years focused on the benefic properties of essential oils (EOs) and their major components, terpenes and terpenoids (that are mostly monoterpenes and sesquiterpenes), and their biological properties. This chapter focuses on terpenoids as important bioactive constituents of EOs. It describes their uses, importance, extraction processes, and classification. The chapter provides an in-depth overview of the latest findings/ research about terpenoids in EOs. It contains a well-prepared background, introduction, classification, chemical tests, bioactivities, as well as the characterization of terpenoids. It also discusses the bioactivities of EOs and that of terpenoids, with regard to their synergetic and/or their antagonistic effects.

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Terpenoids as Important Bioactive Constituents of Essential Oils

Dracocephalum kotschyi essential oils obtained by hydrodistillation (HD), microwave-assisted hydrodistillation (MAHD), and solvent-free microwave extraction (SFME) were investigated by GC-FID (Gas Chromatography-Flame Ionization Detector) and GC-MS (Gas Chromatography-Mass Spectrometry). The percentage of oxygenated compounds was significantly increased from 62.52% in HD to 76.47% in MAHD, and 84.52% in SFME. Conversely, the monoterpene hydrocarbons were decreased from 30.84% in HD to 13.71% in MAHD, and 5.85% in SFME. The main compound in the essential oil obtained by HD is limonene, which accounted for more than 30% of the oil, while the percentage of this compound was reduced to 9.52% in MAHD, and 5.60% in SFME. The percents of other oxygenated compounds such as neral, geranial, geraniol, geranyl acetate, α-terpineol, trans-verbenol, carvon, and trans-carveol were noticeably higher in microwave methods than those present in HD method. In aqueous medium, linear oxygenated monoterpenes may be con...

https://www.tandfonline.com/doi/pdf/10.1080/10942912.2017.1295987

Chemical composition and antibacterial activity of Dracocephalum kotschyi essential oil obtained by microwave extraction and hydrodistillation

Soxhlet, microwave-assisted, and room temperature liquid extraction of oil and bioactive compounds from palm kernel cake using isopropanol as solvent

This study was aimed at comparing the essential oils obtained from Heteromorpha arborescens leaves by Solvent-Free Microwave Extraction (SFME) and Hydrodistillation (HD) methods in terms of their chemical compositions, yield, CO2 emission, and energy consumption. The solvent-free microwave extraction method indicated a higher oil yield of 0.7 mL/200 g (0.35%) as compared to 0.59 mL/200 g (0.295%) obtained through hydrodistillation. GC-MS analysis of the oils revealed a total of 52 chemical components from both methods with the presence of 35 (96.52%) and 30 (71.15%) chemical constituents for HD and SFME, respectively. The major constituents observed in the essential oil extracted by SFME methods include α-pinene (6%), D-limonene (11.27%), β-ocimene (9.09%), β-phellandrene (6.33%), β-mycene (8.49%), caryophyllene (5.96%), and camphene (4.28%). However, in the hydrodistillation method, the oil was majorly composed of a-pinene (4.41%), β-pinene (10.68%), β-ocimene (6.30%), germacrene-D (5.09%), humulene (5.55%), and α-elemene (6.18%). The SFME method was better in terms of saving energy (0.25 kWh against 4.2 kWh of energy consumed), reduced CO2 emission (200 g against 3360 g of CO2), a higher yield, and better quality of essential oil due to the presence of higher valuable oxygenated compounds (8.52%) against that of the hydrodistillation method (2.96%). The SFME method is, therefore, a good alternative for extracting the oils of H. arborescens leaves since the essential oil yield is higher with more oxygenated compounds, considerable energy savings, lower cost, and reduced environmental burden at substantially reduced extraction time (30 min as opposed to 180 min).

/pdf/chemical-composition-of-essential-oils-obtained-from-4lkfterykj.pdf

Chemical Composition of Essential Oils Obtained from Heteromorpha arborescens (Spreng.) Cham. and Schltdl Leaves Using Two Extraction Methods.

Solvent-free microwave extraction (SFME) is proposed as a method for “green” extraction of edible essential oils extensively used in the fragrance, flavour, and pharmaceutical industries and also in aromatherapy. It is a combination of microwave heating and dry distillation, performed at atmospheric pressure without adding any solvent or water. Isolation and concentration of volatile compounds are performed by a single stage. Basil (Ocimum basilicum L.) was extracted with SFME at atmospheric pressure and 373 K for 30 min. The extracted compounds were removed from the aqueous extract by simple decantation, identified by gas chromatography–mass spectrometry (GC-MS). Hydrodistillation (HD) of basil was performed with 400 ml of water for 4.5 h for comparison of the results with those provided by the proposed method. SFME method offers important advantages over HD, viz. shorter extraction times (30 min vs. 4.5 h); better yields (0.13 % vs. 0.11 %); environmental impact (energy cost is appreciably higher for performing HD than that required for rapid SFME), cleaner features (as no residue generation and no water or solvent used); and provides a more valuable essential oil. SFME is a green technology and appears as a good alternative for the extraction of edible essential oils from aromatic plants used in aromatherapy and food industry. Запропоновано використовувати мікрохвильову екстракцію без розчинника (МЕБР) як метод «зеленої технології» для екстракції харчових ефірних олій, які широко використовуються у парфумерній та фармацевтичній промисловості, а також в ароматерапії. Такий метод є поєднанням мікрохвильового нагріву та сухої перегонки за атмосферного тиску без додавання будь-якого розчинника або води. Виділення і концентрування летких сполук відбувається одностадійно. За допомогою вказаного методу проведено екстракцію базиліку (Ocimum Basilicum L.) за атмосферного тиску і 373 К протягом 30 хв. Екстраговані компоненти видалені з водного екстракту простою декантацією та ідентифіковані за допомогою газової хроматографії–мас-спектрометрії (ГХ-МС). Для порівняння отриманих результатів проведено гідродистиляцію (ГД) базиліку з 400 мл води протягом 4,5 год. Доведено, що запропонований МЕБР метод має важливі переваги порівняно з ГД, а саме: скорочення часу екстракції (30 хв проти 4,5 ч); вищий вихід (0,13% проти 0,11%); менший вплив на навколишнє середовище (затрати енергії є значно нижчими), не використовується вода або розчинник і не утворюються залишки; отримується більш цінна ефірна олія. Показано, що метод МЕБР відноситься до «зелених технологій» і є хорошою альтернативою для вилучення харчових ефірних олій з ароматичних рослин, які використовуються в ароматерапії і харчовій промисловості.

http://ena.lp.edu.ua:8080/bitstream/ntb/33676/1/12-213-218.pdf

Intan Dewi

Papers

Solvent-free microwave extraction as the useful tool for extraction of edible essential oils