Comparison between the Chemical Composition of Essential Oil from Commercial Products and Biocultivated Lavandula angustifolia Mill.

The main aim of this study was to assess the differences in the chemical composition of essential oil from biocultivated Lavandula angustifolia in the Thracian Lowland floristic region, Bulgaria, and commercially available products from Bulgarian markets. Following the analytical results conducted with gas chromatography-mass spectrometry, we have established some differences in the chemical composition of the tested samples. The essential oil of biocultivated lavender contained 35 compounds, which represent 94.13% of the total oil. Samples from commercial products contained 28–42 compounds that represent 93.03–98.69% of the total oil. All the examined samples were rich in monoterpene hydrocarbons (1.68–12.77%), oxygenated monoterpenes (70.42–87.96%), sesquiterpene hydrocarbons (4.03–13.78%), and oxygenated sesquiterpenes (0.14–0.76%). The dominant components in all examined samples were linalool (20.0–45.0%) and linalyl acetate (20.79–39.91%). All the examined commercial samples contained linalool and linalyl acetate as was described in the European Pharmacopoeia, but in one of the samples, the quality of linalyl acetate is lower than that recommended in the European Pharmacopoeia.


Introduction
Lavender (Lavandula angustifolia Mill.) is one of the most popular aromatic plants in the Lamiaceae family with origin in the Mediterranean region and is cultivated worldwide for medicinal and commercial purposes [1,2]. Lavandula angustifolia (L. angustifolia) has great economic values as an essential oil-producing plant. Because of its characteristic and pleasant aroma, as well as its therapeutic properties, the essential oil of lavender is of considerable importance in pharmaceutical, cosmetics, perfume, food, and favor industries [3][4][5]. Te foral essential oil of lavender is documented to have therapeutic efects such as antibacterial, antioxidant, antifungal, carminative, sedative, antidepressive, analgesic, and anti-infammatory [3,6,7]. In addition, according to Basch et al., the aroma of lavender is one of the most widely utilized in aromatherapy, considered to be relaxing, with anxiolytic efects [8]. Te multiple therapeutic applications of L. angustifolia are attributed mainly to the presence of volatile bioactive substances contained in the essential oil [4].
Lavender essential oil is usually produced by steam or hydrodistillation from fowering tops, and other used methods for oil extraction are supercritical CO 2 fuid extraction, microwave, ultrasound, and turbohydrodistillation [9]. Te chemical composition of the EO difers according to the extraction technique [5,10]. However, essential oil from L. angustifolia is composed of various constituents, including esters: linalyl acetate, lavandulyl acetate, and geranyl acetate; alcohols: linalool, α-terpineol, and terpinen-4-ol; sesquiterpenes: β-caryophyllene; and monoterpene: cisβ-ocimene [2,4,[10][11][12][13]. Te greater proportion is linalyl acetate and linalool which are considered active constituents, but linalool is considered one of the most examined odorant molecules [14]. Both components are responsible for therapeutic efects. Moreover, all constituents contribute to the synergism of the total therapeutic efect. Today, lavender is cultivated around the world and enjoys continuing popularity for various therapeutic and cosmetic purposes [3,12].
According to Stanev et al., Bulgaria has a long tradition of lavender cultivation and essential oil production dating since the 1900s [15]. Moreover, according to Stanev et al., Bulgarian lavender populations are characterized by high adaptability to the geographic, climate, and soil conditions of the country and consequently high essential oil content and quality [16]. Tis placed Bulgaria as one of the main lavender-growing and essential oil-producing countries, along with France [1,13,17]. Due to the economic value of lavender essential oil, interest in the development of new commercial products has increased. Tis study compares the chemical composition of essential oils from biocultivated L. angustifolia and commercial products in Bulgaria.

Plant Material and Oil
Extraction. L. angustifolia was cultivated in the area of Belashtitsa, Tracian Lowland foristic region, Bulgaria. Te cultivated plant has grown in a continental climate with an average annual temperature of 12.3°C and rendzina soil. Te essential oil was obtained from the air-dried fowering tops of lavender by hydrodistillation using the Clevenger apparatus for 3 h according to the standard procedure described in the European Pharmacopoeia 9 (07/2018:1534) [18]. After completion of distillation, the collected oil was dried over anhydrous sodium sulfate and stored in dark glass vials at 4°C until GC-MS analysis.

Chromatographic Conditions.
Gas chromatographymass spectrometry (GC-MS) was used for the analysis. GC-MS analyses were carried out using Bruker Scion 436-GC SQ MS, Bremen, Germany. Te column used was a Bruker BR-5 ms fused silica capillary (0.25 μm flm thickness and 15 m × 0.25 mm i.d.). Te oven temperature was initially held at 45°C for 1 min and then increased to 140 at 3°C/min, and after that, it was increased to 250°C at 17°C/ min and then held for 1 min. Te fow rate of helium (carrier gas) was 1 mL/min. Te injector split ratio was 1 : 50, and the injection volume was 1 μL. Te range of m/z was 50-350 in the full-scan mode. To compare the spectral data and retention indices of compounds, the Wiley NIST11 Mass Spectral Library (NIST11/2011/EPA/NIH) and the literature were used. Retention index values were calculated and compared with reported values for a C7-C20 series of nalkane standards.

Results and Discussion
Te distilled lavender EO had a strong odour of linalool and linalyl acetate. Its colour was yellow. Te extracted essential oil and commercial essential oils were diluted with hexane and analyzed with GC-MS. Figure 1 shows the chromatogram of the EO of the cultivated lavender.
Te essential oil of the cultivated lavender contained 35 compounds, which represent 94.13% of the total oil. Samples from commercial products contained 28-42, which represent 93.03-98.69% of the total oil. Table 1 shows the chemical composition found in essential oils from biocultivated L. angustifolia (CLA) and those from commercial products (CP 1-7).
Te diference in the composition of lavender essential oils may be due to infuence of cultivation methods and diferent geographic regions on the accumulation of chemical compounds [26][27][28]. According to Bara, some of the exogenous factors such as light and soil (pH and constituents) may increase the concentration of terpenes [29]. It is considered that many enzymes of secondary pathways are UV-B-dependent [29,30]. Hassiotis et al. reported that temperature and the fowering stage have a positive infuence on the EO composition, but rainfall during the fowering period has a negative infuence on EO content [31]. Te linalool content is infuenced by temperature, fower development, and rainfalls, and rainfalls during the harvest period decrease linalool production [31]. Also, the addition of synthetic compounds would afect the diferences in the chemical composition and its concentrations [6,32]. Moreover, according to Filly et. al., the diferent isolation methods of essential oil may also lead to diferences in composition [33]. For further studies, it is recommended conducting a survey on adding synthetic and part synthetic compounds to commercial products containing essential oils. Te method used for analyses of the essential oil chemical profle is also important, and the GC-MS analysis represents well separation and identifcation of volatile compounds [34]. Te method described above could also be used for further analysis.

Conclusions
A total of 50 volatile compounds were found in lavender biocultivated essential oil, which represents 93.17% of the total oil. Te following terpene classes were found in the essential oil from lavender biocultivated essential oil: monoterpene hydrocarbons (11.33%), oxygenated monoterpenes (72.94%), and sesquiterpene hydrocarbons (8.47%). Oxygenated monoterpenes were detected in higher amounts. Te prevailing components from them were linalool (23.13%) and linalyl acetate (31.46%). Volatile compounds found in the commercial products were 28-42, which represent 93.55-98.69% of the total oil. Commercial products were rich in oxygenated monoterpenes, and especially, linalool (24.34-35.32%) and linalyl acetate (20.79-39.91%) were in higher amounts. Te results of this study indicate that the essential oil content and quality of the analyzed commercial products corresponded to the recommendations given in the European Pharmacopoeia.

Data Availability
All data generated and analyzed during this study are included in the manuscript.

Conflicts of Interest
Te authors declare no conficts of interest.