In this study, significant variations were found in the essential oil concentrations, the main attribute of V. jatamansi, among the naturally distributed populations in Chamba region and cultivated sources. The highest oil concentration (0.35%) was registered with the population collected from Kugti and Khani. These differences among the populations were probably due to variations in micro-climatic conditions, soil characteristics, and genetic make-up. The altitude of these two locations is higher. Although the physicochemical properties of the soils were found differences among the locations, no definite correlation was found between soil characteristics and essential oil concentration. Despite the higher altitude, the lowest concentration of oil (0.17%) was registered with the population from Garola. This location is characterized by higher EC (1.07 dS m− 1) and relatively low OC (0.71%) and available N (61.12 kg ha− 1) that might be another cause for the low concentration of essential oil in roots/rhizome. Crop-ecological factors such as light, ambient temperature and soil nutrients availability control the biosynthesis of essential oil47. In the mountainous region, variation in micro-climate is common, and this variation influences the qualitative and quantitative parameters of medicinal and aromatic plants48,49,50. The variations in essential oil concentrations in the wild populations and cultivated populations of V. jatamansi have also been reported earlier31,36,44. Despite proper agronomic practices, the oil concentration in the cultivated population (CSIR-IHBT) was lower than the populations from Kugti and Khani. This result was probably due to altitudinal variations and chemotype differences. The populations difference in terms of oil content has been reported from Himachal Pradesh, and the major chemical constituents and essential oil content are negatively correlated with altitude33. The low percentage of patchouli alcohol with the population from Khani during first cycle of distillation was noticed probably due to the edaphic factor, particularly soil available K content. Patchouli alcohol is synthesized in various stages through cis- farsenylpyrophosphate51.The variations in essential oil composition of V. jatamansi due to growing conditions and location have also been reported44,52. Thus, the population having higher amount of patchouli alcohol could be used for mass multiplication for commercial cultivation. It is also suggested that variation in oil quality can be reduced bycollecting the raw material from the cultivated sources.
Despite 6 h distillation on the first day, some quantities of essential oil of V. jatamansi were obtained up to the third day of distillation for the populations collected from Kugti and Khani and cultivated sources (CSIR-IHBT). The populations of Rupena and Garola also produced oil on the second day. These results were because some compounds of essential oil of V. jatamansi like β-elemene, santalene, and seychellene were not removed from the hypodermal layer in the root cortex region. The outcome is noteworthy, and the result can be used to maximize the recovery of essential oil of V. jatamansi. The effects of duration of distillation time on recovery of essential oil have been reported in many aromatic plants39,42,45,53−58.
In this study maximum of 18 volatile compounds were identified, which contributed up to 81.8% of the total volume (Fig. 2), and the maximum number (16) of volatile compounds were identified with the cultivated source from CSIR-IHBT during third-day distillation (Fig. 2e). This result could be due to the fact that the plants at CSIR-IHBT were grown with proper agronomic practices, which ultimately facilitated better conditions for the synthesis of a large number of compounds compared with other naturally distributed populations. The variations in genetic makeup among the populations may be another reason for changing the chemical profile of essential oil. On the other hand, the minimum number of volatile compounds were identified in the oil obtained at first-day distillation from the Garola population (Fig. 2c). The variations in the number of compounds in the essential oil of V. jatamansi have been reported in the literature4,25,30,59. Thus, it is established from the present study that, irrespective of populations, the number of compounds has been increased either at first-day or on the second day of distillation (Fig. 2a-f).
The variations in compositions of essential oils were found noticeable due to populations and distillation methods (Table 2). The differences in crop-ecology may be another cause of variations in compositions of essential oil among the populations. In this study, variations in oil characteristics and altitudinal were observed (Table 1, 2). The variations in essential oil composition from the different parts of India have been reported in V. jatamansi 31,36,43,52. Patchouli alcohol, the most abundant compound in all the populations, was found noticeable differences, and the maximum concentrations were recorded on the first day of distillation, irrespective of populations (Table 2). The essential oil with different in fractions was probably due to boiling point, degree of solubility, molecular weight, and polarity of the compounds. The extraction of polar compounds during hydro-distillation is easy over that of terpene hydrocarbons60.
Table 1
Geophysical positioning of different locations of sample collection
Location | Altitude (m) | Latitude | Longitude |
Rupena (Chamba) | 1810 | 32°27′68′′ N | 76°04′54′′ E |
Kugti (Chamba) | 2140 | 32°34′35′′ N | 72°27′82′′ E |
Garola (Chamba) | 2003 | 32°25′11′′ N | 72°28′32′′ E |
Khani (Chamba) | 2014 | 32°27′39′′ N | 76°29′1′′ E |
CSIR-IHBT, Palampur | 1354 | 32°06′61′′ N | 76°33′77′′ E |
Saloonie (Chamba) | 2032 | 32°26′43′′ N | 76°32′10′′ E |
The concentration of patchouli alcohol in Saloonie (distilled in traditional method) was substantially lower compared with the rest of the populations distilled on the first day. This result could be due to the fact that patchouli alcohol was lost during the drying and storage or post-harvest practices. Low concentrations of patchouli alcohol were also found in the second and third days' oil for all populations. This result could be due to the fact that hydrolytic reactions occurred in the remaining hydrolat, which leads to the breakage of the functional group in patchouli alcohol.
However, the higher concentrations of β-patchoulene, α-guaiene, α-humulene, and δ-guaiene were found in the Saloonie sample probable due to the generation of more heat during the traditional distillation method. Disproportionation, as well as the cyclization process, occurs in monoterpenes at elevated temperatures61. Moreover, at high temperatures compounds are formed through termination reactions62. Moreover, the higher concentration of humulene epoxide II (2.5% on the second day) makes difference to Garola from other populations.
Interestingly, the concentrations of seychellene were abruptly increased with subsequent days of extraction for all the populations. The use of seychellene compound as a non-selective candidate for inhibitor cyclooxygenase on pre-osteoblast cells has been reported63. The α-santalene, generally used in cosmetic, perfumery, and aromatherapy industries64, was found only in second and third days. The α-santalene is the precursor of α-santalol, which is the main component of sandalwood oil from eastern India65. Similarly, β-elemene was found in the second and third days' oil. β-elemene is a novel anticancer agent and also reported for antitumor activity66. The improvement and/or generation of the new compound during the second and third days was probably due to oxidation, thermal degradation, chemical degradation, eventually a chemical conversion. This finding confirmed that the distillation method can be used to obtain the higher quantity of essential oil of V. jatamansi with variance chemical profiles. For example, if a high-patchouli alcohol oil is desirable, 6 h distillation is required for a single day. Similarly, if high concentrations of seychellene, α-santalene, or β-elemene are desirable, roots/rhizome of V. jatamansi need to be distilled for second and/or third times. The effects of cyclic/repeated distillation on the dynamics of compounds in the essential oil of V. jatamansi are explained in the form of a schematic diagram (Fig. 6).
The results of this study have been proven the hypothesis that crop-ecology, source of materials, and distillation method determine the yield and composition of the essential oil of V. jatamansi. The results of the present study also demonstrate that the species V. jatamansi has wide adaptability, and it can be commercially grown with an altitudinal range of 1354–2140 m. It can also be grown in sandy loam to silty clay soil with a wide pH range of 5.59–8.85 and different nutritional levels.