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The Solvent-Free Microwave Extraction of Essential Oil from Plant Matrices

The Solvent-Free Microwave Extraction of Essential Oil from Plant Matrices. An investigation into the effects of ‘ in situ’ excitation of molecules by microwave radiation. Chemistry Capstone Abstract Ed Elliott, Northeastern Illinois University.

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The Solvent-Free Microwave Extraction of Essential Oil from Plant Matrices

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  1. The Solvent-Free Microwave Extraction of Essential Oil from Plant Matrices An investigation into the effects of ‘in situ’ excitation of molecules by microwave radiation

  2. Chemistry Capstone AbstractEd Elliott, Northeastern Illinois University • Plant material consists primarily of water, cellulose, and essential oils. The essential oils of a plant consist of hydrocarbons and oxygenated compounds. Together these compounds make up the volatile oil that is unique to each plant. These volatile compounds often have properties that may correspond with their use within the plant, for example many are antimicrobial, antiviral, anti-parasitic, or are insecticidal. These compounds also find uses in the cosmetic and food industries. Traditional methods of extraction involve distillation using harmful solvents or large amounts of water. In contrast, the solvent-free microwave extraction (SFME) method puts an end to the use of solvents and also significantly decreases the amount of time and energy required for an extraction. Distillation under microwave radiation also provides for increased selectivity of the distilled compounds which can be both environmentally and economically desirable. In addition, these results provide useful data for the elucidation of the mechanisms of microwave-matter interaction.

  3. A Brief Overview…

  4. A History of Microwaves • Maxwell predicts the existence of electromagnetic waves that travel at the speed of light when he publishes the Treatise on Electricity and Magnetism in 1873 • Mathematically this prediction is a product of the arbitrary addition of an extra term, known as the displacement current, to equations that were previously known to describe electromagnetic behavior Loupy, André. 2006. Microwaves in Organic Synthesis. 2nd ed. Wiley-vch Verlag GmbH & Co

  5. A History of Microwaves and since… Leadbeater N, McGowan C. 2006. Clean, Fast Organic Chemistry: Microwave assisted laboratory experiments. Matthews (NC): CEM Publishing.

  6. A History of Microwaves • The first practical use of radar was by the British in World War II for the detection of German airplanes. • Microwaves were further developed during the war for use in navigation and communications equipment. • Percy Spencer was working for Raytheon in1946 when his serendipitously observed his chocolate bar melt in his pocket when standing in front of a radar transmitter. • The next day Spencer returned with the staple of microwave cooking, popcorn, and observed it pop! • Raytheon went on to patent microwave heating in 1947. • Leadbeater N, McGowan C. 2006. Clean, Fast Organic Chemistry: Microwave assisted laboratory experiments. Matthews (NC): CEM Publishing. • Loupy, André. 2006. Microwaves in Organic Synthesis. 2nd ed. Wiley-vch Verlag GmbH & Co

  7. Microwave-Matter InteractionsHow do we create microwave radiation? Leadbeater N, McGowan C. 2006. Clean, Fast Organic Chemistry: Microwave assisted laboratory experiments. Matthews (NC): CEM Publishing.

  8. Microwave-Matter Interactionswhat is microwave radiation? Leadbeater N, McGowan C. 2006. Clean, Fast Organic Chemistry: Microwave assisted laboratory experiments. Matthews (NC): CEM Publishing.

  9. Microwave-Matter InteractionsEnergy level of microwave radiation • Keep in mind that a photon of microwave radiation at 2.45 Ghz has only0.00001 eV of energy • Compare this value to some other molecular forces: • So how does microwave radiation affect molecules? Loupy, André. 2006. Microwaves in Organic Synthesis. 2nd ed. Wiley-vch Verlag GmbH & Co

  10. Microwave-Matter Interactionscharged particles (ions) Leadbeater N, McGowan C. 2006. Clean, Fast Organic Chemistry: Microwave assisted laboratory experiments. Matthews (NC): CEM Publishing.

  11. Microwave-Matter Interactionspolar molecules Leadbeater N, McGowan C. 2006. Clean, Fast Organic Chemistry: Microwave assisted laboratory experiments. Matthews (NC): CEM Publishing.

  12. Microwave-Matter InteractionsConverting MW radiation to heat • How does this energy really become heat? • Dielectric permeability – Matter-Electromagnetic Wave Interaction • Polarization –- Corresponds to the ε’ term which is ‘real’ - Deals with the movement of electrons within a molecule • Dielectric Loss – - Corresponds to the ε’’ term which is ‘imaginary’- Due to the delay between electromagnetic excitation … and the response of a molecule Loupy, André. 2006. Microwaves in Organic Synthesis. 2nd ed. Wiley-vch Verlag GmbH & Co

  13. Microwave-Matter InteractionsThe nature of dielectric loss How does dielectric loss compare between molecules? Loupy, André. 2006. Microwaves in Organic Synthesis. 2nd ed. Wiley-vch Verlag GmbH & Co

  14. Microwave-Matter InteractionsEffect of superheating and temperature The Arrhenius Equation: Predictor of reaction rates • What does this mean for the rate of reaction? • If we Assume: • A reaction has an energy of activation of 200 kJ/mol • A reaction is normally run at 150˚C

  15. Microwave Extraction of Essential Oilsessential oil constituents So what are we extracting from these plants? • Essential oils have enjoyed a rich history of use in medicine as well as use in cooking and perfume • More recently the bioactivity of these compounds has begun to be examined. The compounds appear to be used by the plant for defense against herbivores, pathogens, as well as countering the growth of fungus The essential oil of most herbs consists primarily of monoterpenes • Hackleman, D. 2007. Microwave Extraction of Peppermint Oil and Comparison to the Current Practice of Steam Distillation [thesis]. Corvallis (OR): Oregon State University. 131 p. • Peter KV. 2001. Handbook of Herbs and Spices, 2nd Edition. Boca Raton (FL): CRC Press.

  16. Microwave Extraction of Essential OilsTerpene Terminology • Isoprene or 2-methyl-1,3-butadiene • “Isoprene Rule” The isoprene rule is credited to Otto Wallach who won the Nobel prize for chemistry in 1910. After determining the structure of several terpenes he was able to show that they were made up of repeating isoprene units • Terpenes Alkanes found in living things that are classified according to the number of isoprene units usually found joined head to tail. Monoterpenes contain two (2) isoprene units, Diterpenes contain four (4) units and so on. There are also names for terpenes that contain an odd number of isoprene units • Isoprenoids Many reactions can leave a terpene molecule functionalized. These functionalized terpenes were once referred to separately as isoprenoids; however, in current use the word ‘terpene’ is usually taken to encompass isoprenoids as well

  17. Microwave Extraction of Essential OilsTerpene Chemistry • Investigation into the formationof terpenes in vivo found that natures isoprene unit of choice is Isopentenyl pyrophosphate. • Isopentenyl pyrophosphate can then be converted, via a couple of enzyme catalyzed hydrogen transfers, to Dimethylallyl pyrophosphate. Carey, Francis A. 2006. Organic Chemistry. 6th ed. Madison (WI): McGraw Hill. 1122-1131 p.

  18. Microwave Extraction of Essential OilsTerpene Chemistry

  19. Microwave Extraction of Essential OilsTerpene Chemistry • The formation of simple monoterpenes proceeds via the enzyme catalyzed creation of a new carbon-carbon bond between the vinylic carbon of isopentenyl pyrophosphate and the allylic carbon of dimethylallyl pyrophosphate • The 10-carbon carbocation product is the same if the reaction occurs in one step or two New C-C Bond Carey, Francis A. 2006. Organic Chemistry. 6th ed. Madison (WI): McGraw Hill. 1122-1131 p.

  20. Microwave Extraction of Essential OilsTerpene Chemistry • The 10 carbon carbocation intermediate can undergo several reactions, one of which is the enzyme catalyzed deprotonation Geranyl pyrophosphate

  21. Microwave Extraction of Essential OilsTerpene Chemistry Limonene Functional groups: (2) C=C double bonds -H+ +H2O α-Terpineol Functional groups: C=C double bond Hydroxide (-OH)

  22. Microwave Extraction of Essential Oilsan overview and timeline

  23. Microwave Extraction of Essential Oilsthe advent of sfme • The solvent-free microwave extraction of essential oils was first described in a publication in 2004 • Fundamentally this was not a novel idea, microwaves had been used to extract material from small samples where the amounts extracted were too small for detection by tradition methods • What was found was not what had been expected. Previous studies suggested they would see the same composition just with increased yields • Gómez N, Witte L. 2001. A simple method to extract essential oils from tissue samples by using microwave radiation. Journal of Chemical Ecology, 26, 11 (2001) 2351-2359. • Lucchesi M, Chemat F*, Smadja J. 2004. Solvent-free microwave extraction of essential oil from aromatic herbs: comparison with conventional hydro-distillation. Journal of Chromatography A, 1043 (2004) 323-327.

  24. Microwave Extraction of Essential OilsPlant structure Velasco, C. 2007. Microwave Extraction of Peppermint Oil and Comparison to the Current Practice of Steam Distillation [thesis]. Corvallis (OR): Oregon State University. 131 p.

  25. Microwave Extraction of Essential Oils Velasco, C. 2007. Microwave Extraction of Peppermint Oil and Comparison to the Current Practice of Steam Distillation [thesis]. Corvallis (OR): Oregon State University. 131 p.

  26. Microwave Extraction of Essential OilsPlant structure Plant surface before (A) and after (B) undergoing thermal stress (Photos taken from Figure 1, page 2355) Gómez N, Witte L. 2001. A simple method to extract essential oils from tissue samples by using microwave radiation. Journal of Chemical Ecology, 26, 11 (2001) 2351-2359.

  27. Microwave Extraction of Essential OilsPlant structure Plant surface before and afterundergoing MW extraction(Photos taken from Figures 7.1 and 7.2 , page 117-118) Velasco, C. 2007. Microwave Extraction of Peppermint Oil and Comparison to the Current Practice of Steam Distillation [thesis]. Corvallis (OR): Oregon State University. 131 p.

  28. Microwave Extraction of Essential OilsExperimental Set Up • Although the equipment is similar to traditional distillation methods the technique is unique • Excess water is reintroduced as it settles out of the essential oil in the reflux system • Allows for the isolation and concentration of essential oils in a single step Velasco, C. 2007. Microwave Extraction of Peppermint Oil and Comparison to the Current Practice of Steam Distillation [thesis]. Corvallis (OR): Oregon State University. 131 p.

  29. Microwave Extraction of Essential OilsThe advent of SFME – General Trends • Yields were found to be nearly identical between tradition hydrodistillation (HD) and SFME; however, the time for extraction was 4.5 hours for HD vs. 30 minutes for SFME • Of the essential oil collected the oxygenated fraction was always greater when extracted with SFME • To reach the extraction temperature of 100˚C took 90 minutes with HD. The same temperature was reached only 5 minutes after heading began using SFME

  30. Microwave Extraction of Essential OilsThe advent of SFME Compounds in green boxes predominated in SFME over HD Compounds in white boxes predominated in HD over SFME

  31. Microwave Extraction of Essential Oilssfme of essential oils from dried plant material • There are several advantages, both economic and environmental, to using dried plants over freshly harvested plants. • Practically, it is often a necessity to be able to conduct these extractions with dried material because processing plants may be located far from the fields. • Plant structure serves to inhibit the loss of essential oils from a plant. For example, in one study less than a 10% of monoterpenes were lost when dried plants were stored at room temperature for over a year. Ramanadhan B. 2005. Microwave Extraction of Essential Oils (from Black Pepper and Coriander) at 2.46 GHz [thesis]. Saskatchewan, Canada: Univeristy of Saskatoon. 151 p. Velasco, C. 2007. Microwave Extraction of Peppermint Oil and Comparison to the Current Practice of Steam Distillation [thesis]. Corvallis (OR): Oregon State University. 131 p.

  32. Microwave Extraction of Essential Oilssfme of essential oils from dried plant material • Dried material presented several challenges during processing including difficulty stirring • Differences were found between plants types in terms of response to applied MW field • Coriander did not show increased extraction with increased field strength perhaps due to differences in essential oil composition • Black Pepper showed linear variability with MW field strength • Rehydration showed improvedextraction efficiency as % H2O added increased Ramanadhan B. 2005. Microwave Extraction of Essential Oils (from Black Pepper and Coriander) at 2.46 GHz [thesis]. Saskatchewan, Canada: University of Saskatoon. 151 p.

  33. Microwave Extraction of Essential Oilssfme of essential oils from dried plant material • Some conclusions drawn from the rehydration of dried pepper…

  34. Microwave Extraction of Essential OilsImproved solvent-free microwave extraction • In traditional SFME the essential oils are distilled using the water found in situ. The excess water is refluxed back to the microwave where it can continue to act as a microwave absorber • There is apparently not enough water remaining in dried plant material to allow for adequate absorption of the microwave energy • What if another stronger microwave absorber was added in place of water? Wang Z, Ding L, Li T, Zhou X, Wang L, Zhang H, Liu L, Li Y, Liu Z, Wang H, Zeng H, He H. 2006. Improved solvent-free microwave extraction of essential oil from dried Cuminumcymimum L. and Zanthoxylumbungeanum Maxim. Journal of Chromatography A, 1102 (2006) 11-17.

  35. Microwave Extraction of Essential OilsExperimental Set Up – Improved SFME • The experimental set-up for improved SFME involves three major changes: • The addition of a mechanical stirrer • The addition of powdered CIP • H2O separated from the essential oil is not returned to reflux Wang Z, Ding L, Li T, Zhou X, Wang L, Zhang H, Liu L, Li Y, Liu Z, Wang H, Zeng H, He H. 2006. Improved solvent-free microwave extraction of essential oil from dried Cuminumcymimum L. and Zanthoxylumbungeanum Maxim. Journal of Chromatography A, 1102 (2006) 11-17.

  36. Microwave Extraction of Essential OilsImproved solvent-free microwave extraction CIP [Carbonyl Iron Powder] • Composed of up to 99.8% elemental Fe • First iron pentacarbonyl (Fe(CO)5) is purified through distillation, which then undergoes thermal decomposed to give spherically grained carbonyl iron powder • The CIP can then be treated depending on the intended application though coating, milling, sorting by size, etc. • Advantages: The material is a readily available, commonly used, and has a very high capacity for magnetic absorption

  37. Microwave Extraction of Essential OilsImproved solvent-free microwave extraction Wang Z, Ding L, Li T, Zhou X, Wang L, Zhang H, Liu L, Li Y, Liu Z, Wang H, Zeng H, He H. 2006. Improved solvent-free microwave extraction of essential oil from dried Cuminumcymimum L. and Zanthoxylumbungeanum Maxim. Journal of Chromatography A, 1102 (2006) 11-17.

  38. Microwave Extraction of Essential OilsImproved solvent-free microwave extraction • Benefit: - Least amount of water used • Disadvantage:- Loss of oxygenated compounds recovered Wang Z, Ding L, Li T, Zhou X, Wang L, Zhang H, Liu L, Li Y, Liu Z, Wang H, Zeng H, He H. 2006. Improved solvent-free microwave extraction of essential oil from dried Cuminumcymimum L. and Zanthoxylumbungeanum Maxim. Journal of Chromatography A, 1102 (2006) 11-17.

  39. Microwave Extraction of Essential OilsImproved solvent-free microwave extraction Wang Z, Ding L, Li T, Zhou X, Wang L, Zhang H, Liu L, Li Y, Liu Z, Wang H, Zeng H, He H. 2006. Improved solvent-free microwave extraction of essential oil from dried Cuminumcymimum L. and Zanthoxylumbungeanum Maxim. Journal of Chromatography A, 1102 (2006) 11-17.

  40. Microwave Extraction of Essential OilsTerpene Chemistry Limonene Functional groups: (2) C=C double bonds -H+ +H2O α-Terpineol Functional groups: C=C double bond Hydroxide (-OH)

  41. Microwave Extraction of Essential OilsTheoretical Explanations • (1) Oxygenated isoprenoids are more reactive and given the short period necessary for distillation they simply do not have time to react during extraction • (II) Microwaves favorably excite the more polar molecules giving the oxygenated isoprenoids the energy necessary to undergo the phase transition • (speculative) The oscillating electric field present in a microwave oven seems to favor the presence of more polar transition states.

  42. Implications for future use of MWGreen benefits

  43. Implications for future use of MWPromising Applications • The use of hetero-catalysts that are MW absorbers • The use of ionic liquids under MW heating • Increasing the rate of reactions when conditions are at a high temperature for a long period of time • Increasing the specificity of reactions • The further use of MW radiation for separations

  44. References[Page 1 of 3] • Benkaci-Ali F, Baaliouamer A, Meklati BY. 2006. Kinetic Study of Microwave Extraction of Essential Oil of Nigella sativa L. Seeds. Chromatographia, 64 (2006) 227-231. • Carey, Francis A. 2006. Organic Chemistry. 6th ed. Madison (WI): McGraw Hill. 1122-1131, 1141 p. • Demirbaş A. 2002. Biodiesel from vegetable oils via transesterfication in supercritical methanol. Energy Conversion and Management, 43 (2002) 2349-2356. • Flamini G, Tebano M, Cioni PL, Ceccarini L, Ricci AS, Longo I. 2007. Comparison between the conventional method of extraction of essential oil of Laurusnobilis L. and a novel method which uses microwaves applied in situ, without resorting to an oven. Journal of Chromatography A, 1143 (2007) 36-40. • Gómez N, Witte L. 2001. A simple method to extract essential oils from tissue samples by using microwave radiation. Journal of Chemical Ecology, 26, 11 (2001) 2351-2359.

  45. References[Page 2 of 3] • Hackleman, D. 2007. Microwave Extraction of Peppermint Oil and Comparison to the Current Practice of Steam Distillation [thesis]. Corvallis (OR): Oregon State University. 131 p. • Hjeresen D, Schutt D, Boese J. 2000. Green Chemistry and Education. Journal of Chemical Education, 77, 12 (2000) 1543-1546. • Lassen A, Ovesen L. 1995. Nutritional Effects of Microwave Cooking. Nutrition and Food Science, 4 (1995) 8-10. • Leadbeater N, McGowan C. 2006. Clean, Fast Organic Chemistry: Microwave assisted laboratory experiments. Matthews (NC): CEM Publishing. • Loupy, André. 2006. Microwaves in Organic Synthesis. 2nd ed. Wiley-vch Verlag GmbH & Co. • Lucchesi M, Chemat F*, Smadja J. 2004. Solvent-free microwave extraction of essential oil from aromatic herbs: comparison with conventional hydro-distillation. Journal of Chromatography A, 1043 (2004) 323-327.

  46. References[Page 3 of 3] • McKee, Trudy. McKee, James R. 2003. Biochemistry: The Molecular Basis of Life. 3rd ed. Madison (WI): McGraw Hill. 161-186, 3444-348. • Peter KV. 2001. Handbook of Herbs and Spices, 2nd Edition. Boca Raton (FL): CRC Press. • Ramanadhan B. 2005. Microwave Extraction of Essential Oils (from Black Pepper and Coriander) at 2.46 GHz [thesis]. Saskatchewan, Canada: Univeristy of Saskatoon. 151 p. • Saoud AA, Yunus RM, Aziz RA, Rahmat AR. 2005. Study of Eucalyptus Essential Oil Acquired by Microwave Extraction. Proceedings of the ISHS WOCMAP III: Quality, EfficiancySafty Processing & Trade in MAPs. Acta Horticulture, 679 (2005) 173-179. • Wang Z, Ding L, Li T, Zhou X, Wang L, Zhang H, Liu L, Li Y, Liu Z, Wang H, Zeng H, He H. 2006. Improved solvent-free microwave extraction of essential oil from dried Cuminumcymimum L. and Zanthoxylumbungeanum Maxim. Journal of Chromatography A, 1102 (2006) 11-17. • Watanabe F, Abe K, Fujita T, Goto M, Heimori M, Nakano, Y. 1998. Effects of Microwave Heating on the Loss of Vitamin B12 in Foods. Journal of Agricultural Food Chemistry, 46 (1998) 206-210.

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