Introduction

The genus Lavandula comprises about 39 species worldwide. Among them, L. angustifolia Mill. (Lamiaceae) is an important perennial aromatic plant and is native to the Mediterranean region. The strong aromatic characteristics of L. angustifolia refer to its plant leaves, stalks and flowers covered with glands (Zuzarte et al., 2010). It is extensively cultivated in different regions of the World, especially for essential oil (EO) (Akgün et al., 2000). In folk medicines, L. angustifolia is used to treat various ailments such as stress, rheumatism, epilepsy, gastrointestinal disorders, pain, anxiety and nervous disorders (Hajhashemi et al., 2003; Koulivand et al., 2013). Further, this plant has been widely used in aromatherapy, cosmetics, eco-friendly pesticide, liqueurs and beverages, in addition to pharmaceutical and perfumery industries. Previous scientific studies reported that L. angustifolia has various therapeutic properties such as antibacterial, sedative, spasmolytic and antiviral activities (Cavanagh and Wilkinson, 2002; Piccaglia, 1998; Woronuk et al., 2011).

The chemical composition of the essential oil of L. angustifolia is chiefly characterized by a high percentage of linalool and linalyl acetate with a considerable amount of terpinene-4-il and lavandula acetate. This oil also contains eucalyptol (1,8-cineol) and camphor as well as trace amounts of other components (Pokajewicz et al., 2021). Previous studies found that there has been massive variation in the concentration of major components in the essential oil of L. angustifolia, linalool (25－54%) and linalyl acetate (21－45%) (Caputo et al., 2016; Carrasco et al., 2016). In China, linalyl acetate (28.89%) was the most abundant component in the essential oil from the dry inflorescences of L. angustifolia followed by linalool (24.30%) and caryophyllene (7.89%) (Chen et al., 2020). The variation in the composition of essential oils may be attributed to various biotic and abiotic factors. The chemical components of essential oil from plants were determined primarily by their genotype. The secondary influences are environmental factors, ontogenic factors and morphogenetic futures (Détár et al., 2020; Landmann et al., 2007). The quality of the essential oil of lavender has been determined by the origin of lavender oil, pleasant aroma and desired chemical components (Beale et al., 2017; Bejar, 2020). The steam distillation method is commonly used for extracting essential oil from lavender which helps the enrichment of volatiles (Détár et al., 2020; Dong et al., 2020).

In the present study, the L. angustifolia plants were selected from two different geographically remote locations such as Seorak Mountain (Northern part of South Korea) and Jiri Mountain (Southern part of South Korea). Mainly, L. angustifolia is commercially cultivated for more than 10 years as a crop for essential oil in Seorak and Jiri Mt. regions. However, there has been no information on EO of L. angustifolia in Jiri Mountain and Seorak Mountain. Therefore, L. angustifolia might have been adapted gradually to Korean climatic conditions. Hence, the chemical composition might be changed in L. angustifolia. Further, there is no detailed study on the essential oil chemical composition of L. angustifolia cultivated in Seorak and Jiri mountains. Hence, the present study aimed to compare the essential oil composition of L. angustifolia cultivated in Seorak and Jiri mountains by gas chromatography-mass spectrometry (GC-MS) analysis.

Materials and Methods

Essential oil

The aerial parts of L. angustifolia were collected at Jeollabuk-do ARES Herb & Wild Plants Experiment Station, Namwon, Jeollabuk-do; N 35°25'02.47 E 127°31'34.12 (Jiri mountain) and at Lavender Village Farm, Goseong, Gangwon-do; N 38°20'55.03" E 128°24'53.78" (Seorak mountain), South Korea. The L. angustifolila was harvested at the flowering stage in June 2022 and air dried at 50°C. Then, the essential oil was isolated from L. angustifolia by steam distillation method. The steam distillation was performed at 100°C for 90 min. The essential oil isolation was carried out in triplicates and the yield (%) was calculated as volume (mL) of the isolated oil per 100 g of the dry weight material. The isolated essential oil was dried using anhydrous sodium sulfate and stored at 4°C for further analysis.

Gas chromatography-mass spectrometry (GC-MS) analysis

The identification of the essential oil components from L. angustifolia was performed using a Varian CP3800 gas chromatograph coupled with a Varian 1200L mass detector (Varian, CA, USA). The GC-MS was equipped with a VF-5MS polydimethylsiloxane capillary column (30 m × 0.25 mm × 0.25 μm). The oven temperature was started at 50°C and then programmed to 250°C at a rate of 5°C/min. The injector temperature was 250°C and the ionization detector temperature was 200°C. Helium was the carrier gas (1 mL/min) and the injected volume of the sample was 1 μL with a split ratio of 10:1. For mass spectra, an electron ionization system with ionization energy of 70 eV was used. The mass range was 50－500 m/z. The determination of the percentage composition of each component was based on the normalization of GC peak areas. The identification of the essential oil components was based on the comparison of their retention indices (RIs) relative to a homologous series of n-alkanes (C₈-C₂₂) and mass spectra from the National Institute of Standards and Technology (NIST, 3.0) library and literature data (Adams, 2007). Calculation of the peak area of each compound relative to the total peak area of the whole chromatograph presented the percentage of each essential oil constituent.

Results

The EO was extracted from aerial parts of L. angustifolia by steam distillation from Seorak and Jiri Mountains and the yields were 0.04 ± 0.01% and 1.27 ± 0.38%, respectively. The color of Seorak EO was orange, but Jiri Mt.’ EO was pale yellow. The EOs chemical composition of L. angustifolia from the Seorak and Jiri Mountains was presented in Table 1.

In total, 44 components were identified in the essential oils of L. angustifolia from Seorak and Jiri by the GC-MS technique. In these, 21 compounds were detected in both Seorak and Jiri samples. Further, 14 components were identified only in the essential oil of L. Angustifolia from Seorak Mountain. Whereas 9 components were identified only in the essential oil of L. angustifolia from Jiri Mountain.

The essential oil of L. angustifolia from Seorak Mountain contains a total of 35 different components, which accounted for 84.23% of the total essential oil. The essential oil of L. angustifolia (Seorak Mt.) contains 10 monoterpenoids, 7 monoterpenes, 7 sesquiterpenes, 4 sesquiterpenoids, 3 alcohols, 3 esters and 1 ketone. Among them, linalool (28.72 ± 0.35%) is the most abundant compound in the essential oil of L. angustifolia (Seorak Mt.) followed by linalyl formate (27.53 ± 0.42%). β-caryophyllene (9.32 ± 0.12%), lavandulyl acetate (4.24 ± 0.06%), β-ocimene (3.83 ± 0.08%), isoborneol (1.93 ± 0.02%), α-terpineol (1.35 ± 0.04%) and caryophyllene oxide (1.04 ± 0.05%) were also detected in considerable amount in this essential oil. The rest of the components were identified with less than 1%.

In the case of L. angustifolia essential oil from Jiri Mountain, 30 different compounds were identified from 96.22% of the total oil. In this essential oil, 6 monoterpenes, 8 monoterpenoids, 4 alcohols, 5 sesquiterpenes, 3 esters, 2 sesquiterpenoids, 1 phenol and 1 ketone were identified. Similar to the essential oil isolated Seorak Mountain, linalool (46.15 ± 0.09%) and linalyl formate (39.81 ± 0.15%) were the most abundant component in the essential oil of L. angusifolia from Jiri Mountain. However, the concentration of linalool and linalyl formate was higher in Jiri sample than Seorak sample. Further, β-caryophyllene (3.09 ± 0.03%), isoborneol (1.22 ± 0.01%) and β-farnesene (1.22 ± 0.02%) were detected in significant level.

Discussion

L. angustifolia is one of the most important medicinal and aromatic plants and its essential oil is used in the perfumery, cosmetics and therapeutic industries (Despinasse et al., 2020). The essential oil of L. angustifolia has a strong fragrance due to the presence of many aromatic components. Apart from flavor and fragrance purposes, L. angustifolia essential oil possesses numerous biological properties such as antioxidant, anti-depressant, anti-inflammatory, antimicrobial, relieving neuropathic pain, toxoplasma activity, antileishmanial activity, cardioprotective, antimutagenic, neuroprotective and anxiolytic properties (Cavanagh and Wilkinson, 2002; Miastkowska et al., 2021). L. angustifolia essential oil is a potential alternative in food and industrial production due to its highly acclaimed properties in various fields. Although many studies reported on the essential oil composition of L. angustifolia growing in different parts of the world, significant variations were observed in its composition both quantitatively and qualitatively. The concentration of major essential oil components invariably differs according to geographical locations (Demasi et al., 2018).

In the present study, a total of 44 components were identified in the essential oils of L. angustifolia both from Seorak and Jiri Mountains. In these, 12 monoterpenoids, 9 monoterpenes, 8 sesquiterpenes, 5 esters, 4 sesquiterpenoids, 4 alcohols, 2 ketones and 1 phenol were identified. A recent study found that alcohols (38.14%), esters (37.41%), alkenes (17.28%) and ketones (1.18%) were major components in the essential oil of L. angustifolia in China (Guo and Wang, 2020). In this study, the predominant components in the essential oils of L. angustifolia are linalool, linalyl formate and β-caryophyllene. Similarly, Adaszyńska et al. (2013) reported that the primary component of essential oil from five varieties of L. angustifolia was linalool (23.9－15.8%). However, Mekonnen et al. (2019) found that eucalyptol (52.36%), camphor (11.91%), γ-terpinene (8.78%) and endoborneol (7.59%) were identified as major components in the essential oil from fresh leaves and flowers of L. angustifolia cultivated in Ethiopia. The main constituents in the essential oil of L. angustifolia cultivated in Belgrade were 1,8-cineole (7.1－48.4%), linalool (0.1－38.7%), borneol (10.9－27.7%), β-phellandrene (0.5－21.2%) and camphor (1.5－15.8%). In the essential oil of L. angustifolia from Algeria, linalool (22.35%), linalyl acetate (21.80%), trans-ocimene (6.16%) and 4-terpineol (5.19%) were major components (Djenane et al., 2012). Major components, linalool and linalyl acetate were mainly responsible for the pleasant aroma of L. angustifolia essential oil (Łyczko et al., 2019).

A high amount of linalool (46.15 ± 0.09%) and linalyl formate (39.81 ± 0.15%) were detected in the essential oil of L. angustifolia from Jiri Mountain compared to that of the essential oil from Seorak Mountain. According to previous studies, linalyl acetate was one of the predominant components in the essential of L. angustifolia. However, linalyl formate was identified as the second major component in the essential oils of L. angustifolia from both Seorak and Jiri Mountains. Linalool is an important fragrant compound that is commonly perceived as a pleasant aroma with physiological effects on human beings like inducing calmness and enhancing sleep. Linalool is present in the essential oils of more than 200 plant species of different families (Stashenko and Martínez, 2008). The linalool-rich essential oil exhibited various biological activities and enhanced the specific scent of cosmetic products (Kamatou and Viljoen, 2008). The previous study found that the essential oil components (monoterpene and sesquiterpene hydrocarbons and oxygenated monoterpenes) of L. angustifolia had strong antimicrobial activities (Bogdan et al., 2021; Hussain et al., 2008; Ruberto and Baratta, 2000).

The essential oil of L. angustifolia from Poland contained 22.7% of monoterpenes, whereas, the essential oil of L. angustifolia collected from Ukraine contained only 5.8% of monoterpenes. This variation in the same species of L. angustifolia is due to different geographical origins of the plant (Białoń et al., 2019). Lakušic et al. (2014) reported the seasonal variations in the chemical composition of the essential oils obtained from the same individual of L. angustifolia cultivated in Belgrade. Another study indicated that the latitude (sea distance) and altitude influenced on the essential oil composition of L. angustifolia. In particular, latitude had an influence on morphological as well as phytochemical traits (Demasi et al., 2018). Previously, numerous studies demonstrated that the variation in the essential oil composition is highly influenced by genetic variability of the species, plant parts, developmental stage, in addition to various abiotic factors, including season, soil, climate, etc. (Rathore et al., 2022). It is well-known that the interaction between the plant and environment mostly contributes to the expression of phytochemicals (Demasi et al., 2018). These factors influence the biosynthetic pathways of the plant and affect the concentration of the main constituents (Al‐Badani et al., 2017). In the present study, the variation of the chemical components between L. angustifolia essential oils from Seorak and Jiri Mountain might be due to the geographical locations and agronomic factors such as fertilizer application and weather.