Antique Lavender Essential Oil from 1945, its chemical composition and enantiomeric distribution

Nat. Volatiles & Essent. Oils, 2016; 3(2): 20-25 Satyal and Pappas RESEARCH ARTICLE Antique lavender essential oil from 1945, its chemical composition and enantiomeric distribution Prabodh Satyal* and Robert S. Pappas Essential Oil University, New Albanay, IN 47150, USA *Corresponding author. Email: Abstract Properly stored lavender from 1945 was collected in French market and Gas Chromatography and Mass Spectrometry (GCMS) analysis was carried out to see possible chemical transformation and chemical composition. Total of 102 peaks (100% components) were identified, out of them 10 were oxidized minor components (total 0.41%). The lavender essential oil was dominated by the linalool (40.8%), terpinen-4-ol (9.9%), α-terpineol (3.5%), linalyl acetate (16.4%), lavandulyl acetate (3.8%), and trans-caryophyllene (2.2%). Enantiomeric distribution of major monoterpenoids were also measured. Keywords: Lavender oil-1945, linalool, linalyl acetate, terpinen-4-ol, oxidation, enantiomeric distribution, storage of essential oils. Introduction Lavandula angustifolia Mill. (also known as lavender) comprised of more than 39 known species is one of the most popular essential oils in aromatherapy from Lamiaceae family. The flowering plant of lavender (Lavandula angustifolia or Lavandula officinalis) is used to produce lavender essential oils. It is sweet aromatic and colourless essential oil. It is widely used in aromatherapy and fragrance industry because of its biological activities and aromatic potentials. Proper storage of essential oils is always mandatory since lavender does not contain any antioxidant molecules in its essential oil (Hagvall et al., 2008). Presence of water molecules and aerial exposure causes severe oxidation of essential oils (Guenther, 1948). The major components of lavender are linalool, linalyl acetate and caryophyllene (Sköld et al., 2007). Out of them trans-caryophyllene is most susceptible to oxidation to produce oxidized product (caryophyllene oxide) which is the least sensitizing molecule (Sköld et al., 2006). Highly oxidized lavender produces hydroxide, epoxides and hydroperoxides of linalool, linalyl acetate, and caryophyllene (Nilsson et al., 2008). Autooxidation happens in the allylic positions of double bonds in linalool and linalyl acetate (C6-C7) (Sköld et al 2007). They are found to possess sensitizing effect on skin (Nilsson et al., 2008), however there are few contact allergies have been reported (Letizia et al., 2003). So, proper handling and storage of fragrance compounds are always advised (Turek & Stintzing, 2013). Numerous studies on lavender essential oils have been carried out, however this is the first report on chemical composition and enantiomeric distribution of 71 year old lavender so far from our understanding. Materials and Methods Plant Material Essential oil sample was purchased in 1945 in Paris, France. The essential oil was stored on amber glass container in refrigerator until analysis was carried out. 20 Nat. Volatiles & Essent. Oils, 2016; 3(2): 20-25 Satyal and Pappas Gas Chromatographic – Mass Spectral Analysis The essential oil of lavender was analyzed by GC-MS using a Shimadzu GCMS-QP2010 Ultra operated in the EI mode ((electron energy = 70eV), scan range = 3.0 scans/sec), and GCMS Solution software. The GC column was Zebron ZB-5MS fused silica capillary column with a (5% phenyl)-polymethyl siloxane stationary phase a film thickness of 0.25 mm. The career gas was helium with a column head pressure 80 psi and flow rate of 1.37 ml/min. Injector temperature was 250 oC and the ion source temperature was 200 oC, increase in temperature rate 2 oC/min to 260 oC. The GC oven temperature program was programmed for 50 oC initial temperature, increase in rate 2 oC/min to 260 oC. A 5% w/v solution of the sample in CH2Cl2 was prepared and 0.1 µL was injected in splitting mode (30:1). Identification of the oil components was based on their retention indices determined by reference to a homologous series of n-alkanes, and by comparison of their mass spectral fragmentation patterns with those reported in the literature (Adams, 2007), and stored in the MS library. Chiral Gas Chromatographic-Mass Spectral Analysis Chiral analysis of the lavender essential oils was performed on a Shimadzu GCMS-QP2010S operated in the EI mode ((electron energy=70eV), scan range = 3.0 scans/sec). GC equipped with a Restek B-Dex 325 capillary column (30 m×0.25 mm ID×0.25 _m film). Oven temperature was started at 50 ◦C, and then gradually raised to 120 ◦C at 1.5 ◦C/min. The oven was then raised to 200 ◦C at 2 ◦C/min and held for 5 min. Helium was the carrier gas and was flow rate was maintained at 1.8ml/min. Samples were diluted 3% w/v with CH2Cl2 and then a 0.1 µL sample was injected in a split mode with a split ratio of 1:45. Results and Discussion Essential Oil Composition The lavender oil was purchased commercially in 1945 and stored in dark bottle for 71 years. A total of 102 peaks (100% components) were identified, out of them 10 oxidized minor components (total 0.41%) were detected (see Table 1). The studied lavender is the least oxidized as compared to studies carried out in stability studies of tea tree oil (Trachida et al., 2010). The lavender essential oil was dominated by the linalool (40.8%), terpinen-4-ol (9.9%), α-terpineol (3.5%), linalyl acetate (16.4%), lavandulyl acetate (3.8%), and transcaryophyllene (2.2%). These results are quantitatively different than any result previously published in a significant review paper (Lawrence, 2012) and from ISO standard of French lavender (ISO lavender, 2016). Out of the published research high terpinen-4-ol, high linalool, and low linalyl acetate has not previously been reported (Lawrence, 2012), the maximum amount of terpinen-4-ol was reported as 5.0-6.2% (Chemat et al., 2006; Pavela, 2006). Increase in oxidation products like linalool oxide, caryophyllene oxide indicates autoxidation of linalool and caryophyllene (Misharina et al., 2003; Sköld et al., 2008). Linalool readily undergoes autooxidation to form cyclized molecule: furanoids and pyranoids (Sköld et al., 2008), so the concentration of furanoids and pyranoids in this report is relatively high as compared to freshly distilled lavender (Lawrence, 2012). Whereas due to large bulky acetate group, linalyl acetate is unable to form cyclized furanoid, and pyranoids. Sesquiterpene oxide is formed from oxidation of sesquiterpene (Hădărugă et al., 2014). Ascaridole glycol cis and trans along with epoxide are observed as oxidized product of terpinen-4-ol (Tranchida et al 2010). 21 Nat. Volatiles & Essent. Oils, 2016; 3(2): 20-25 Satyal and Pappas Enantiomeric distribution of lavender essential oil was also studied (Table-2), which is similar to previously studied lavender essential oil (Baser et al., 2005). Total 70.64% of monoterpene was enantiomerically analyzed to see the distribution. L-linalool, L-linalyl acetate, D-Terpinen-4-ol, an (...truncated)