List of medicinal plants and their identified essential oil evaluated under microwave assisted solvent-free extraction.
Abstract
Essential oil is one of an important concentrated liquid that possesses many physical, chemical and pharmacological properties. Extraction of essential is one of the main issues in the last decade. Conventional treatment consisting of hydrodistillation and steam distillation has many disadvantages and finds difficult to purify essential oil. Now, it is much easier to extract essential oil with the invention of new greener technologies that reduce the involvement of solvent, decrease the extraction time, energy and descent the interaction of the concentrated volatile liquid with atmospheric oxygen through the application of vacuum.
Keywords
- solventless extraction
- solvent-free extraction
- essential oil
- extraction technology
- green extraction
1. Introduction
Essential oils are complex concentrated liquids comprise of volatile compounds. They have been extracted from numerous plant [1]. They have been widely used as a food preservative (eucalyptus essential oil, thyme), cosmetic preparation (lavender oil), antimicrobial (lemon grass, cumin, fennel), and anticancer agent (lemon grass,
2. Solventless extraction in a closed system
Solventless extraction of essential oil was designed in a closed system under reduced pressure using a vacuum and compared the results with the conventional methods such as hydrodistillation. The quality and quantity of essential oil extracted from
3. Solvent-free microwave extraction
Solvent-free microwave extraction (SFME) of volatile natural substances was the first to patent in 2004. Farid Chemat et al. invented a method of extraction of essential oil consisting of a microwave oven with a microwave chamber for receiving the biological material and a condensation chamber. It was first tested on different spices such as ajowan (
Medicinal plants | Identified essential oil | Pharmacological activities | Reference |
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2-Methyl-5-(1-methylethyl)-bicyclo[3.1.0]hex-2-ene, 1-Methylethylideneyl-cyclohexane, α-Pinene, Camphene, β-Phellandrene, β-Pinene, β-Myrcene, β-Phellandrene 3-Carene, 4-Carene, 1-Methyl-2-(1-methylethyl) benzene, d-Limonene, Eucalyptol, 1-Methyl-4-(1-methylethyl)-1,4-cyclohexadiene, 1-Methyl-4-(1-methylethylidene)-cyclohexene, β-Terpineol, 6,6-Dimethyl-2-methylene-bicyclo[2.2.1]heptan-3-one, 4-Methyl-1-(1-methylethyl)-3-cyclohexen-1-ol, Pulegone, Cuminal 4-(1-Methylethyl)-1-cyclohexene-1-carboxaldehyde 2-Ethylidene-6-methyl-3,5-heptadienal, α-Proyl-benzenemethanol, 4-(1-Methylethyl)-1,4-cyclohexadiene-1-methanol, 6-Isopropylidene-1-methyl-bicyclo[3.1.0]hexane, Caryophyllene, 2,6-Dimethyl-6-(4-methyl-3-pentenyl)-bicyclo[3.1.1]hept-2-ene, 7,11-Dimethyl-3-methylene-1,6,10-dodecatriene, 2-Isopropyl-5-methyl-9-methylene-bicyclo[4.4.0]dec-1-ene, Octahy-dro-3,8,8-trimethyl-6-methylene-1H-3a,7-methanoazulene, Thujopsene, 1-(1,5-Dimethyl-4-hexenyl)-4-methylbenzene 5-(1,5-Dimethy-4-hexenyl)-2-methyl-1,3-cyclohexadiene, Copaene, 1-Methyl-4-(5-methyl-1-methylene-4-hexenyl-cyclohexene, β-Sesquiphellandrene, Caryophyllene oxide, Carotol | N.F | [16] | |
a-Pinene, Camphene, b-Pinene, Myrcene, a-Phellanderene, a-Terpinene c-Terpinene, Linalool, 1 1,8-Cineole, Camphor, Borneol, b-Caryophyllene, Trans b-ocimene, cis-Sabinene hydrate, Verbinone, Terpene-4-ol, Myrtenol, Bornyl acetate, Cis-jasmone, a-Humulene, Pentasiloxane Caryophyllene, 1,5-Diphenyl 2H-1,2,4 triazoline, 1-Methyl-2,4-nitrophenyl benzimid, 2-Methoxy-3,8-dioxocephalotax-1-ene, 1,2-Benzenedicarboxylic acid, 9-Octadecenoic acid, Docosanoic acid | Anti-bacterial | [31] | |
Cedrene [1S-(1a,4a,7a)]-1,2,3,4,5,6,7,8-octahydro-1,4,9,9-tetramethyl-4,7-methanoazulene Caryophyllene, 10S,11S-himachala-3(12),4-diene, 4-(2,6,6-Trimethyl-2-cyclohexen-1-yl)-2-butanone, (E)-4-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3-buten-2-one, 1,2,3,4,4a,5,6,8a-Octahydro-7-methyl-4-methylene-1-(1-methylethyl)naphthalene, (R)-c-cadinene 4-(2,6,6-Trimethyl-1-cyclohexen-1-yl)-3-buten-2-one, (1a,4ab,8aa)-1,2,3,4,4a,5,6,8a-Octahydro-7-methyl-4-methylene-1-(1-methylethyl)naphthalene, Albicanol, [1R-(1a,4ab,8aa)]-decahydro-1,4a-dimethyl-7-(1-methylethylidene)-1-naphthalenol, Calarene epoxide, (1R,4S,11R)-4,6,6,11-tetramethyltricyclo[5.4.0.0(4,8)]undecan-1-ol, 1,4,4a,5,6,7,8,8a-Octahydro-2,5,5,8a-tetramethyl-1-naphthalenemethanol, (-)-Isolongifolol, acetate, 1R,4S,7S,11R-2,2,4,8 tetramethyltricyclo[5.3.1.0(4,11)]undec-8-ene, [3S-(3a,5a,8a)]-1,2,3,4,5,6,7,8-octahydro-a,a,3,8-tetramethyl-5-azulenemethanol acetate, | Anti-oxidant | [26] | |
a-Pinene, Camphene, 2-Carene, D-Limonene, o-Cymene, gamma-Terpinene, Thymol methyl ether, L-Bornyl acetate, Cyclocopacamphene, Ylangene, beta-bourbonene, (+)-Sativene,(−)-beta-Elemene, Germacrene-D, (E)-(b)-Farnesene, (E)-a-bergamotene, Elixene, alpha-amorphene,(−)-beta-Chamigrene, Beta-bisabolene, b-maaliene, c-cadinene, b-himachalene, a-Chamigrene, (+)-a-Longipinene, (+)-Cuparene, b-Caryophyllene, Guaiene, (+)-Ledene, L-calamenene | Anti-oxidant | [22] | |
3,6-Dimethyl-octane, Naphthalene, Dodecane, 6-Ethyl-undecane, 4-Methyl-dodecane, 4-Ethyl-undecane, 4,6-Dimethyl-dodecane, 1-Methyl-naphthalene, 2,6,11-Trimethyl-dodecane, α-Longipinene, 2-Methyl-tridecane, (+)-Cyclosativene, Ylangene, α-Copaene, Tetradecane, Longifolene, Caryophyllene, β-Selinene, α-Bergamotene, α-Himachalene, Humulene, Alloaromadendrene, α-Bisabolene, 2,4-Bis(1,1-dimethylethyl)-phenol, б-Cadinene, Hexadecane, Norphytane | Anti-microbial activities | [21] | |
Sabinene, Octen 3 ol, β-Pinene, Heptanol, β-Myrcene, p-Cymene, Limonene, 1,8-Cineole, β-Ocimene, γ-Terpinene, Fenchone, Linalool, Camphor, Menthol, α-Terpineol, Methyl chavicol, Nerol, Neral, Geraniol, Geranial, α-Terpinenyl acetate, Neryl acetate, α-Copaene, Geranyl acetate, β-Bourbonene, β-Cubebene, β-Elemene, Methyl eugenol, β-Caryophyllene, α-Bergamotene, α-Humulene, β-Farnesene, Germacrene-D, γ-Cadinene, Δ-Cadinene, α-Bisabolene, β-Bisabolene, Spathulenol, Caryophyllene oxide, α-Cadinol | N.A | [25] | |
Isorhamnetin, isorhamnetin 3-O-glucoside, isorhamnetin 3- O-rutinoside and quercetin 3-O-glucoside | Anti-oxidant | [32] | |
1, 8-cineole, Camphor, Borneol, p-cymene, Limonene, Cryptone, isobornyl formate, cumin aldehyde, Valerianol, α-pinene | Anti-bacterial activity | [33] | |
a-Thujene, a-Pinene, Sabinene, b-Pinene, D2-Carene, a-Terpinene, Camphene, (Z)-b-Ocimene, allo-Ocimene, Myrcene, Limonene, c-Terpinene, p-Cymene, Octan-3-ol, Eugenol, Geranyl acetone, Hexahydrofarnesylacetone, Octacosane, Phytol, Caryophyllene oxide, T-Cadinol, a-Cadinol, T-Muurolol, a-Copaene, b-Elemene, b-Cubebene, b-Bourbonene, a-Humulene, Caryophyllene, Germacrene-D, c-Cadinene, epi-Sesquiphellandrene, d-Cadinene, Menthyl acetate, Bornyl acetate, Menthol, Chrysanthenone, Piperitenone, Piperitenone oxide, Isopulegonen, Pulegone, Piperitone, cis-Sabinene hydrate, 1,8-Cineole, Dihydrocarveol, trans-Sabinene hydrate, Menthone, Isomenthone, Terpinen-4-ol, a-Terpineol | N.A | [24] |
Instrumentation | Extraction conditions | Results | Reference |
---|---|---|---|
Reactor (500 mL), microwave oven, agitator, shielded non-invasive thermometry system, transformer with maximum output power is 800 W with 2450 MHz of microwave irradiation frequency (MIF). | 100 g of sample and 20 g of carbonyl iron powder (CIP) were added inside the reactor, stirred, heated (85 W) for 30 min at 100°C with speed of rotation (200 rpm), concentrated outside the microwave oven by a cooling system | CIP helps to improve the microwave absorption capacity than water and is faster (30 min) than conventional method | [16] |
The multi-mode reactor (2 × 800 W, 2450 MHz), rotating microwave diffuser, plasma coated PTFE cavity, circulating cooling system at 5°C | 250 g of Rosmarinus leaves were placed into the reactor without the addition of water or any solvent | Higher amounts of oxygenated monoterpenes were found as compared to conventional method | [31] |
Microwave-accelerated reaction system (1000 W, 2450 MHz) multimode microwave reactor armed with a TFT multicolour liquid crystal screen, a power sensor (power range 0–1000 W), an infrared temperature sensor, a temperature controller and electromagnetic stirrer | 200 g plant material was moistened prior to extraction by soaking in certain proportions of water (weight basis) for 1 h and then draining off the excess water. After that, the moistened materials were subjected to the microwave oven cavity and a condenser was used to collect the extracted essential oils in a pre-setting procedure. | A maximal extraction yield of 0.33% was achieved under optimal conditions of extraction time 34 min, irradiation power 520 W and humidity 51% 16 | [26] |
Multimode microwave reactor, temperature Infrared sensor with maximum output power is 700 W, microwave rotating diffuser that ensures homogeneous microwave distribution | A 100 g of |
Identification of optimum parameters was as follows; extraction time 30 min, irradiation power 385 W and the moisture content of |
[22] |
The microwave-accelerated reaction system with multimode microwave reactor (2.45 GHz), IR temperature sensor, an electromagnetic stirrer, a time calculator controller, circulating water-cooling system | 200 g plant materials were wetted before extraction by soaking in a certain proportion of water for 1 h, and then removal the excess water. The wetted material was placed in the reaction flask and connected to a glass reaction flask | The optimal parameters were extraction time 44 min, irradiation power 660 W, and humidity 68%, with extraction yield of 0.330 (%, w/w) | [21] |
Microwave oven (EMM-2007X, Electrolux, 20 l, the maximum delivered the power of 800 W) with a wave frequency of 2450 MHz. A round bottom flask with a capacity of 1000 ml was placed inside the oven and was connected to the three-way adapter and Liebig condenser through the hole. Then, the hole was closed with PTFE to prevent any loss of the heat inside | 150 g of fresh plant materials were placed in the reaction flask and heated by microwave irradiation with 400 W (50% power) for 30 min without adding any solvent or water. During the process, the vapor passed through the condenser outside the microwave cavity where it was condensed. Essential oil and water were simply separated by decantation. The essential oil was collected in amber vials, dried over anhydrous sodium sulfate and stored at 277 K | SFME exhibit shorter extraction times as compared to conventional method (30 min vs. 4.5 h) and better yields (0.13% vs. 0.11%) | [25] |
Milestone EOS-G microwave laboratory oven having a multimode microwave reactor (2.45 GHz) with a maximum delivered the power of 900 W. The extraction vessels are made from Pyrex and have a capacity of 1000 mL with a temperature sensor optic fiber which was inserted in the center of embedded plant material and also in the reactor above the matrix | 400 g of sea buckthorn press cake was heated using a fix power density 1 W·g−1 without the addition of solvents or water. The crude extract was collected continuously in a graduated cylinder. The extraction was continued until no more extract was obtained or overheating was detected | This method exhibit shorter extraction time (15 min), cleaner feature (no solvent or water used) and extraction of valuable flavonoids (Isorhamnetin, isorhamnetin 3-O-glucoside, isorhamnetin 3-O-rutinoside and quercetin 3-O-glucoside) at optimized power (400 W) | [32] |
Microwave apparatus, 2450 MHz with maximum power 1000 W and ACTE0 sensor for temperature monitoring. The power of the oven was 500 W for 10 min. The temperature was achieved at 95°C, and the extraction was carried out for 25 min | 30 g of dried |
It helps to extract more oxygenated compounds | [33] |
Vacuum and nitrogen gas was applied on and off to remove air and replacing it with nitrogen in a closed system. At the end of the extraction process water and oil was separated and anhydrous sodium sulfate was used to dry the excess water | Fresh leaves of aromatic plants were grinded and to break them into smaller pieces and increasing the area of contact. Then, the grind leaves were put in a flask which was connected to another flask as a receiving flask. Firstly, the raw material was cooled down to a very low temperature to prevent decomposition and to avoid premature oil evaporation | Essential oil produced is lighter in color, higher yield, contains a cleaner, better purity and produced a stronger aroma compared to the essential oil produced from hydro-distillation | [12] |
4. Conclusion
The term Solvent-less and solvent-free extraction have been used as synonymous with each other. Extraction of essential oil using these methods has a number of advantages such as fast action, cleanliness, green method, low energy output as compared to traditional extraction method. However, microwave extraction needs extra care before use as it may cause some negative effect on human health. There are many opportunities and modification possible in term of purification of essential oil by applying in combination with other extraction technique.
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