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Development of a green alternative procedure for simultaneous separation and quantification of clove oil and its major bioactive constituents Ming-Chi Wei, Pei-Hui Lin, Show-Jen Hong, Jin-Ming Chen, and Yu-Chiao Yang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b01263 • Publication Date (Web): 20 Sep 2016 Downloaded from http://pubs.acs.org on September 26, 2016
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ACS Sustainable Chemistry & Engineering
Development of a green alternative procedure for simultaneous separation and quantification of clove oil and its major bioactive constituents
Ming-Chi Wei,‡ Pei-Hui Lin,¶ Show-Jen Hong,§ Jin-Ming Chen,‡ and Yu-Chiao Yang∗,§
‡
Department of Applied Geoinformatics, Chia Nan University of Pharmacy and
Science, Tainan 71710, Taiwan. ¶
Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA §
Department and Graduate Institute of Pharmacology, Kaohsiung Medical University, Kaohsiung 80708, Taiwan.
Short title: Ultrasound-assisted supercritical CO2 extraction of clove oil
*To whom correspondence should be addressed. Tel: +886-7-3121101 ext. 2139 ext. 13 Fax: +886-7-3234686 E-Mail:
[email protected] 1
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Abstract:
Clove buds are a good source of oil, which can be used as a food flavor and traditional Chinese medicine. To isolate clove oil and its major bioactive constituents, a green alternative procedure employing ultrasound-assisted supercritical carbon dioxide (USC–CO2) extraction combined with gas chromatography/mass spectrometry was developed, and its performance was compared with those of conventional processes. The green USC−CO2 process saves time, solvent, energy and raw materials without chemical waste, while achieving superior yields of clove oil and major bioactive constituents. The solubility of clove oil and fictitious solubility of eugenol in SC–CO2 have been predicted for the first time at various temperatures (32–50°C) and pressures (9.0–28.5 MPa). Furthermore, solubility data correlated well with three density-based models, Chrastil, Kumar-Johnston, and Bartle, and the overall average absolute relative deviations (AARD%) were 0.22%, 0.92%, and 4.91%, respectively. Using correlation results, the enthalpies for clove oil were approximated. The total heat of the solution, heat of the solvation, and heat of the vaporization for clove oil were 9.83, 19.03 and -9.69 kJ/mol, respectively.
Keywords: clove oil, eugenyl acetate, eugenol, β-caryophyllene, α-humulene, ultrasound-assisted supercritical CO2 extraction, solubility.
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■ INTRODUCTION
The dried flower buds of Syzygium aromaticum (L.) Merr.& Perry (Family Myrtaceae), commonly known as clove, is a well-known food flavor for exotic food preparations.1 Cloves are also well-known for being rich in oils (approximately 15– 20%), which are commonly known for a wide spectrum of pharmacological and biological activities, such as antibacterial, insecticidal, antioxidant, fungicidal, antiviral, antitumor, anti-inflammatory, antiphlogistic, antivomiting, analgesic, antispasmodic, anticarminative, kidney reinforcing, hepatoprotective, anesthetic and cytotoxic properties.1,2,3 The major components of clove oil are usually considered to be eugenol, eugenyl acetate, β-caryophyllene and α-humulene, which are credited with the above-mentioned wide spectrum of biological activities.1,3,4 Additionally, clove oil is used extensively in food products, perfumery and cosmetic products.1,3 The variety of applications for clove oils, increasing numbers of studies have been focused on finding efficient and optimal methods for the production and extraction of oil from cloves. A number of different techniques have been used to isolate clove oil, such as hydrodistillation,5 steam distillation,5,6 some traditional organic solvent extraction methods (maceration, shaking, microwave-assisted extraction,6 solvent extraction,5,7 ultrasound-assisted extraction4) and supercritical carbon dioxide (SC-CO2) extraction.5,8 Among them, although the SC-CO2 extraction method is a high capital investment, it accounts for superior quality and yields while consumes less operating time, temperature and organic solvent. However, due to its high-pressure operating conditions, it is also difficult to apply mechanical stirring within the method, which would result in a decrease in the 3
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extraction kinetics. The application of ultrasonic energy to assist the SC-CO2 (USC-CO2) extraction process produced a relevant increase in the extraction yield of oil together with a noticeable reduction in energy consumption and an increase in extraction rate.9 Therefore, to obtain the required extraction yields within shorter processing times or with higher economic efficiency, combination of SC-CO2 with ultrasonic energy (USC-CO2) had been developed in this study. In this work, the effects of pressure and temperature on the extraction yield and oil solubility from cloves were studied in ultrasonic-assisted SC-CO2 (USC-CO2) process. Solubility data were further correlated and discuss with three density-based models, which has not been reported previously.
■ EXPERIMENTAL
Materials. Three different batches of dried clove buds were generously supplied by Chuang Song Zong Pharmaceutical Co. Ltd. (Kaohsiung, Taiwan) and authenticated and deposited by Department and Graduate Institute of Pharmacology, Kaohsiung Medical University (Kaohsiung, Taiwan). The moisture contents were 9.36%, 8.73% and 8.05% as determined by Karl Fischer volumetric titration. Carbon dioxide (99.99%) and helium (99.99%) were purchased from Yun-Shan Gas Co. Ltd. (Tainan, Taiwan), and n-hexane was bought from Merck Co. (Darmstadt, Germany). Eugenol, β-caryophyllene, α-humulene and eugenyl acetate were procured as reference substances from Sigma Chemical Co. (St. Louis, MO, USA).
Ultrasound-assisted SC-CO2 Extraction. 20 g of ground cloves mixed with 2-mm stainless steel balls was placed in the 152-mL stainless steel extraction vessel. After 4
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desired temperature (32–50°C) and pressure (9.0–28.5 MPa) were reached, a static extraction was performed for 15 min (with ultrasound assistance) and 30 min (without ultrasound assistance), followed by a dynamic extraction that varied from 5 to 210 min (with/without ultrasound-assisted) at the CO2 flow rate of 0.08–0.74 g/min. The equipment and details of extraction methods are described in Supporting Information (Figure S1) and referred to our previous work.10
Steam distillation (SD). 100 g of ground cloves in 500 ml flask was submitted to steam distillation. The distillation was conducted until no more essential oil was obtained and the essential oil collected at the exit of the glass condenser was separated by the action of gravity.11
Heat-reflux extraction (HRE). 5 g of ground cloves were extracted using 100 ml of boiling n-hexane for 240 min under magnetic stirring at 300 rpm for 240 min. The details were described in previous work.12
Gas chromatography-mass spectrometry (GC-MS). Analysis was performed with a Thermo Finnigan PolarisQ Ion Trap with a TRACE GC/MSn equipped with a fused-silica capillary column (30 m × 0.25 mm, 0.25-µm film thickness, model HP-5 MS, Agilent Technologies Co., Ltd., Palo Alto, USA) and a mass spectrometer from the same company, which was operated in EI mode (energy voltage, 70 eV). Further details on the separation/identification conditions were the same as those described previously.13
Gas chromatography (GC). GC analyses were performed by using a GC-FID system 5
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(Shimadzu, model CG-14A, Kyoto, Japan) equipped with a flame ionization detector (FID) and a fused-silica DB-5 capillary column (30 m × 0.25 mm × 0.25 µm, J & W Scientific, Folsom, CA). The separation and identification were described in detail by Yang et al.13
Statistical analysis. All yields and compositional analyses were calculated by assuming a moisture-free environment. The mean and standard deviation (SD) of the mean were calculated by using six experiments. An analysis of variance (ANOVA) was performed by using Tukey’s method with a significance level of P
