optimized method to analyze rose plant volatile organic ...· headspace solid phase microextraction
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Journal of Biosciences and Medicines, 2017, 5, 13-31 http://www.scirp.org/journal/jbm
ISSN Online: 2327-509X ISSN Print: 2327-5081
DOI: 10.4236/jbm.2017.53003 March 10, 2017
Optimized Method to Analyze Rose Plant Volatile Organic Compounds by HS-SPME-GC-FID/MSD
Mohammed Ibrahim1,2, Manjree Agarwal1, Giles Hardy1, Yonglin Ren1*
1School of Veterinary and Life Science, Murdoch University, Murdoch, Australia 2College of Agriculture, University of Babylon, Babylon, Iraq
Abstract A method involving Headspace solid-phase microextraction (HS-SPME) fiber combined with gas chromatography (GC) coupled with flame ionization de-tection (FID) and gas chromatography with mass spectrometry (GC-MS) was developed and optimized to investigate volatile organic compounds (VOCs) from different tissues (flowers, leaves, stems, rhizosphere and whole plants) of Floribunda and Hybrid Tea roses (intact and cut). Three-phase fiber 50/30 m divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) was used. Two types of chambers (Tedlar bag and glass jar) were evaluated for collection of VOCs and glass jar was selected. Absorbed compounds on the fiber were completely desorbed in the GC injector port at three desorption times (5, 10 and 15 min), and 5 min at 250C was used. The maximum extraction effi-ciency for flowers tissues (equilibrium absorption) was achieved 2 h after fiber exposure in the headspace for intact and cut Floribunda and Hybrid Tea flowers. Under the optimized HS-SPME and GC-FID/MS conditions, 1h ex-traction time was chosen for intact and cut Floribunda and Hybrid Tea leaves and stems. The results demonstrated that 5 cm depth was selected for root and soil part (rhizosphere) for both rose cultivars, and 6 h and 12 h extraction time of VOCs from rhizosphere was achieved for Floribunda and Hybrid Tea, respectively. One hour was chosen for VOCs released from whole rose plants for both cultivars. In this study, the VOC profiles of two rose cultivars were characterized by the optimized HS-SPME-GC method. The different tissues of rose plants gave wide range of the VOCs; also the chromatograms of different cultivars were quite different and the specific VOC pattern of rose types de-pends on the species. Results from this study demonstrate the feasibility of this method for identifying VOCs from two rose cultivars and the potential use of this method for physiological studies on rose plants or on other flori-culture plants.
How to cite this paper: Ibrahim, M., Agarwal, M., Hardy, G. and Ren, Y.L. (2017) Optimized Method to Analyze Rose Plant Volatile Organic Compounds by HS- SPME-GC-FID/MSD. Journal of Biosciences and Medicines, 5, 13-31. https://doi.org/10.4236/jbm.2017.53003 Received: February 21, 2017 Accepted: March 7, 2017 Published: March 10, 2017
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Keywords Optimization, Rose tissues, VOCs, SPME-GC-FID/MS, Floribunda, Hybrid Tea
Roses (Rosa hybrida L.) are an important ornamental plant of the family Rosacea. The genus Rosa includes about 100 - 200 species and more than 18,000 cultivars  . The family Rosacea is recognized for its high economic value and use in agro-based industries, especially in cosmetics, perfumes, food and pharmaceutical industries  . Roses are the most important cut flower crop in the world, with Australia exporting about 6,720,221 stems with an approxi-mate value of $3,743,000 in 2016. In contrast, Australia imports about 204,001,778 stems at a cost of about $63,838,000 in 2016 . The main industrial application of roses comes from the perfume industry, which relies on different scented rose varieties     . Among these varieties are the Hybrid Tea rose and Floribunda rose cultivars, both of which are modern roses. The Hybrid Tea rose is a cross between European and Chinese roses  . Floribunda is the result of crossing hybrid tea with Polyantha .
Roses emit a wide range of volatiles organic compounds (VOCs) from flowers, leaves, stem and roots . These can be extracted by various techniques, such as hydro-distillation, microwave extraction, and solvents, all of these methods require grinding and adding solvents. Thus some chemicals which are released from the plants will not appear. In contrast, recently solid phase microextraction (SPME) was developed to capture VOCs which is used to profile and quantify these compounds. Most studies have focused on volatile emissions from flowers or fruits, with little is known about emissions from other plant tissues, such as leaves, stems, roots and even the whole plant including rhizosphere soil. There are many methods for obtaining rose volatiles, such as rose oil (essential oil) and these methods have been extensively reviewed    . Unfortunately, the aroma of extracted oils rarely represents the delicate natural aroma of flori-culture plants, because of thermal artefacts produced during the steam distilla-tion process (which typically occurs at 60C - 70C) . Likewise, other extrac-tion methods using ground samples and solvents also frequently fail to capture the natural aromas   . Studies by   indicated that essential oils extracted from Chrysanthemum did not fully represent the delicate natural aroma. To identify VOCs produced by roses or other plants, it is necessary to develop sensitive, non-destructive, rapid and systematic methods from different plant tissues that are also cost effective. There are no studies about the use of headspace solid phase microextraction HS-SPME for fresh intact or excised tis-sues obtained from roses. The SPME method is widely used for the analysis of volatile compounds, and it is successfully employed to monitor the extraction of aromatic components for Jasminum . The HS-SPME technique is a new,
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simple, fast, and highly sensitive and solvent-free sample preparation technique for the extraction of volatile compounds   .
The HS-SPME technique also provides interesting results when gas chroma-tography (GC) is combined with Flame Ionization Detector (FID) and mass spectrometric detection (MS). The SPME technique gives simultaneously tens or hundreds of possible volatile compounds, but it must be optimized for the vola-tiles being targeted  . There are many factors that affect the optimiza-tion of extraction conditions. These include the correct fibre and an appropriate chamber for capturing the VOCs, the temperature used during extraction and the extraction time from the headspace . In the past, optimization experi-ments have only analysed a variable at a time, this approach does not allow any investigation into the possible interactions between variables, and hence it is not possible to explore fully the opportunities for optimization . To date, there has been no systematic work on optimizing extraction conditions for individual tissues of rose plants or the whole plant. Therefore, developing robust and prac-tical methods for the extraction of VOCs from rose plants has important com-mercial implications for the aroma industry. The objective of the present work is the systematic optimization of HP-SPME methods, and analysis of VOCs from different rose tissues, and intact plants by gas chromatography coupled with Flame Ionization Detector and Mass Spectrometry (GCFID/MS).
2. Materials and Methods 2.1. Reagents
Ethanol was purchased from MERK (high-performance liquid chromatography [HPLC] grade). An n-hexane 95% was purchased from Sigma-Aldrich Australia, catalogue number 270504-2L, and the n-Alkane standard (C7-C30) was pur-chased from Sigma-Aldrich Australia, catalogue number 49451-U.
2.2. Apparatus and Equipment
An Agilent Technologies gas chromatograph 7829A (serial number CN14272038) fitted with a HP-5MS column non-polar (30 m x 0.25 mm, film thickness 0.25 m, RESTEK, catalogue number 13423), with a flame ionization detector (FID) was used throughout the study. Three replicate solid phase microextraction (SPME) fibres 50/30 m divinylbenzene/ carboxen/polydimethyl siloxane (DVB/ CAR/PDMS; Sigma-Aldrich Australia, catalog number 57347-U), attached to a manual SPME holder (Supelco Inc.) were used. The fibres were conditioned as recommended by the manufacturer before analyses were conducted. In order to collect samples from the rhizosphere profile of rose plants, hollow sample probes 20 cm long were made from stainless steel, and one millimetre diameter holes were cross drilled at 5 mm increments from the tapered end up the probe to 3.5 cm from the top. A 1/8 cm compression fitting with a septum was installed into the top of the probe to facilitate insertion of the SPME fibre. A single tube was inserted into each pot to capture the VOCs. For whole plants, a glass chamber (30 35 60 cm) with a 5 mm port drilled into one side, into which a septum
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was placed to accommodate the SPME fibre and was designed for the extraction of VOCs (Table 1). For excited rose tissues, a 500 ml Pyrex (Silverlock Packag-ing; JG2701 FL) glass jar with a 5 mm port drilled into one side, into which a septum was placed (Table 1). As a comparison to the glass jar, Tedlar bag about 0.5 L was purchased from SKC, Inc (catalogue number 236-001, 0.5 L from SKC). Aluminium foil 150 m 44 cm (Vital Packaging Company) was used to cover the glass chambers and jars top which VOCs were extracted and also used for extract VOCs from intact stems (Table 1).
2.3. Plant Material and Maintenance
This study was conducted on two-year-old rose plants (Hybrid Tea cv. Mr Lin-coln) and (Floribunda cv. Iceberg), purchased from Dawsons