Results of the comparative study of Nigella sativa L. seeds oils composition under Bukhara region conditions

Composição química comparativa de óleos de sementes de Nigella sativa L. cultivadas nas condições regionais de Bukhara

Abstract

The chemical composition of Nigella sativa L. (black cumin) seed oil has been extensively studied in various regions worldwide; however, data specific to Uzbekistan’s agro-climatic zones remain limited. This study aims to characterize the fatty acid, sterol, and volatile composition of Nigella sativa seeds cultivated in the Bukhara region and to compare the results with international literature. Bukhara is characterized by hot, arid summers and low precipitation, which may influence lipid profiles. Oil yield, fatty acid composition, sterol and triterpene content, and essential oil constituents were analyzed using GC–FID, GC–MS, and 1H-NMR spectroscopy. Results revealed that Bukhara-grown Nigella sativa seeds have an oil content of 36.5 ± 0.5%, with linoleic acid (59.1 ± 0.3%), oleic acid (23.5 ± 0.2%), palmitic acid (11.8 ± 0.1%), and thymoquinone (2.3 ± 0.1%) as major compounds. Compared to other regions, Bukhara samples showed higher thymoquinone accumulation, highlighting their potential as valuable raw material for pharmaceutical and nutraceutical industries.

Keywords:
Nigellasativa L.; fatty acids; sterols; essential oils; Bukhara region

Resumo

A composição química do óleo de semente de Nigella sativa L. (cominho preto) tem sido amplamente estudada em várias regiões do mundo; no entanto, os dados específicos das zonas agroclimáticas do Uzbequistão continuam limitados. Este estudo tem como objetivo caracterizar a composição de ácidos graxos, esteróis e compostos voláteis das sementes de Nigella sativa cultivadas na região de Bukhara e comparar os resultados com a literatura internacional. Bukhara é caracterizada por verões quentes e áridos e baixa precipitação, o que pode influenciar os perfis lipídicos. O rendimento do óleo, a composição de ácidos graxos, o teor de esteróis e triterpenos e os constituintes do óleo essencial foram analisados usando GC-FID, GC-MS e espectroscopia 1H-NMR. Os resultados revelaram que as sementes de Nigella sativa cultivadas em Bukhara têm um teor de óleo de 36,5 ± 0,5%, com ácido linoleico (59,1 ± 0,3%), ácido oleico (23,5 ± 0,2%), ácido palmítico (11,8 ± 0,1%) e timoquinona (2,3 ± 0,1%) como principais compostos. Em comparação com outras regiões, as amostras de Bukhara apresentaram maior acúmulo de timoquinona, destacando seu potencial como matéria-prima valiosa para as indústrias farmacêutica e nutracêutica.

Palavras-chave:
Nigella sativa L.; ácidos graxos; esteróis; óleos essenciais; região de Bukhara

1. Introduction

Nigella sativa L. (Ranunculaceae), commonly known as black cumin or black seed, is one of the most widely used medicinal plants in traditional systems such as Ayurveda, Unani, and Islamic medicine (Ahmad et al., 2013; Sultana, 2015). Historical records trace its use back to ancient Egypt and Mesopotamia (Zohary et al., 2012). The seeds contain up to 70% oil, rich in essential fatty acids, sterols, triterpenes, and phenolic compounds, with thymoquinone being the most significant bioactive constituent (Amin and Hosseinzadeh, 2016; Woo et al., 2012).

Numerous studies have investigated the chemical composition of Nigella sativa oils in different agro-ecological zones. Egyptian samples showed high levels of linoleic acid and p-cymene (Ramadan, 2007; Gharby et al., 2015), Indian varieties exhibited lower thymoquinone content but higher monoterpene levels (Singh et al., 2005), while Tajik samples reached thymoquinone levels up to 2.6% (Goryainov et al., 2020). Russian samples showed relatively low thymoquinone content (~0.7%) (Goryainov et al., 2020), and Moroccan studies highlighted sterol variability depending on soil fertility and cultivation practices (Gharby et al., 2015).

Beyond composition, pharmacological studies confirm the therapeutic potential of Nigella sativa oil in cardiovascular diseases, diabetes, liver disorders, and neurodegenerative conditions (Bamosa et al., 2010; Kaatabi et al., 2015; Abdelmeguid et al., 2010; Ismail et al., 2008). Clinical trials have demonstrated improvements in inflammatory biomarkers and metabolic health following supplementation (Darand et al., 2019; Bamosa et al., 2010). Given its wide range of applications, Nigella sativa has also entered the nutraceutical industry (Al-Ali et al., 2008).

Despite global research efforts, no studies have comprehensively examined Nigella sativa seeds cultivated in Uzbekistan. The extreme continental climate of the Bukhara region—with hot, dry summers (up to 45°C), cold winters, and limited precipitation—creates stress conditions that may stimulate secondary metabolite biosynthesis (UzHydromet, 2018).

Therefore, this study aims to fill this knowledge gap by analyzing the chemical composition of Nigella sativa seeds grown in Bukhara and comparing the results with international data. Specifically, the study aims to determine and comparatively evaluate the oil yield, fatty acid profile, sterol composition, and volatile constituents of Nigella sativa L. seed oils cultivated in the Bukhara region using GC–FID, GC–MS, and 1H-NMR techniques, and to assess the influence of regional agro-ecological conditions on their chemical characteristics.

Comparative data on the chemical composition of Nigella sativa seed oils cultivated under Bukhara’s agro-ecological conditions are still lacking, highlighting the novelty and scientific relevance of this work.

2. Materials and Methods

Nigella sativa L. seeds were collected from experimental fields in Jondor (39.7785° N, 63.1152° E) and Vobkent (39.8540° N, 63.4001° E) districts, Bukhara region, Uzbekistan, during the harvesting seasons of 2019–2021. Seeds were obtained from the local cultivar and a total of n = 5 plants per field were sampled. The collected seeds were air-dried and stored at 4°C prior to extraction.

The soil in the experimental fields is light loamy with low organic matter (1.2%) and pH 7.8. The region experiences an average annual precipitation of approximately 150 mm and hot, dry summers with maximum temperatures up to 45°C (UzHydromet, 2018).

Powdered seeds (50 g) were extracted using a Soxhlet apparatus with n-hexane (200 mL) for 6 hours. Extracts were dried under vacuum at 40°C, and oil yield was calculated relative to the dry seed weight (Goryainov et al., 2020).

Fatty acids were converted to methyl esters (FAMEs) and analyzed by GC-FID (Agilent 7890B) using reference standards (Gharby et al., 2015). The injection volume was 1 μL, carrier gas was helium at 1 mL/min, and the oven program ranged from 150°C to 250°C at 5°C/min.

Sterols and triterpenes were analyzed by GC-MS (Agilent 7890B coupled with 5977 MSD) after separation of unsaponifiable fractions (Khoddami et al., 2013). Injector temperature was 250°C, and mass spectra were recorded in electron ionization mode (70 eV).

Essential oils were analyzed by GC-MS and quantified using area normalization (Darand et al., 2019).

Thymoquinone content was determined by 1H-NMR spectroscopy (Bruker 400 MHz) using deuterated chloroform (CDCl3) as solvent, with 16 scans per sample (Amin and Hosseinzadeh, 2016).

All experiments were conducted in triplicate, and results are reported as mean ± standard deviation (SD).

3. Results

The average oil yield of Nigella sativa L. seeds cultivated in the Bukhara region was 36.5 ± 0.5%, which is comparable to previously reported values from Tajikistan (37.2%), Egypt (35.5%), and Russia (37.8%) (Goryainov et al., 2020; Gharby et al., 2015) (Figure 1).

Figure 1
Oil yield (%) of Nigella sativa L. seeds from Bukhara region compared with samples from other countries (Tajikistan, Egypt, Russia).

Gas chromatography analysis identified 12 fatty acids. Linoleic acid (C18:2, 59.1 ± 0.3%) was the most abundant, followed by oleic acid (C18:1, 23.5 ± 0.2%), palmitic acid (C16:0, 11.8 ± 0.1%), and stearic acid (C18:0, 2.8 ± 0.1%). Minor fatty acids, including myristic, arachidic, and behenic acids, were present at <1%. The polyunsaturated/saturated fatty acid ratio (PUFA/SFA) was 4.2, and the linoleic/oleic ratio was approximately 2.5 (Figure 2).

Figure 2
Fatty acid composition (%) of Nigella sativa L. seed oil cultivated in Bukhara region.

Analysis of the unsaponifiable fraction revealed that β-sitosterol (27.4 ± 0.4%) and cycloartenol (23.2 ± 0.3%) were the major sterols, consistent with Moroccan Nigella sativa oils (Gharby et al., 2015). Minor sterols included stigmasterol (6.2 ± 0.1%), campesterol (4.8 ± 0.1%), and avenasterol (3.7 ± 0.1%), while cholesterol was negligible (0.8 ± 0.05%).

GC–MS analysis of the essential oil fraction identified more than 40 volatile compounds. The major constituents were p-cymene (47.6 ± 1.2%), thymoquinone (18.9 ± 0.5%), thymol (4.1 ± 0.1%), and α-thujene (9.8 ± 0.3%) (Figure 3).

Figure 3
GC–MS chromatogram of the essential oil extracted from Nigella sativa L. seeds grown in Bukhara region.

¹H-NMR spectroscopy confirmed GC–MS results and allowed precise quantification of thymoquinone content, which was 2.3 ± 0.2%. This value is higher than Russian (0.7%) and Indian (1.0%) samples, approaching the upper range recorded in Tajikistan (2.6%) (Goryainov et al., 2020).

4. Discussion

The comparative analysis of Nigella sativa seed oils obtained from the Bukhara region and previously reported data from other geographical areas indicates that arid and high-temperature environmental conditions primarily affect the biosynthesis of secondary metabolites rather than the general lipid profile. In particular, thymoquinone and p-cymene contents were markedly higher in the Bukhara samples, whereas the overall fatty acid composition remained within the ranges reported for seeds cultivated in Tajikistan, Egypt, Russia and India.

This comparative pattern suggests that environmental stress associated with high solar radiation and limited water availability in the Bukhara region selectively enhances secondary metabolic pathways, while maintaining relatively stable primary lipid metabolism. The observed regional variability of thymoquinone therefore reflects the adaptive biosynthetic response of Nigella sativa to local agro-ecological conditions. These results support the pharmacological relevance of Bukhara-grown seeds, particularly in relation to their antioxidant, anti-inflammatory and anticancer potential (Woo et al., 2012; Randhawa and Alghamdi, 2011).

Furthermore, the sterol profile of the Bukhara samples is comparable to that reported for other producing regions, but the relatively high proportion of β-sitosterol strengthens the nutraceutical value of the oil, especially for applications related to cholesterol reduction. The present comparative evaluation therefore identifies the Bukhara region as a promising cultivation area for producing high-value Nigella sativa raw materials with enhanced bioactive properties (see Figure 4).

Figure 4
Comparative analysis of Nigella sativa L. seed oil composition from different geographical regions.

Based on these findings, future studies should focus on agronomic optimization strategies and genotype–environment interactions in order to clarify the mechanisms controlling secondary metabolite accumulation. In addition, further clinical investigations are required to validate the biological activity of Nigella sativa oil produced under the agro-climatic conditions of the Bukhara region (Bamosa et al., 2010; Kaatabi et al., 2015).

5. Conclusion

This study provides the first comprehensive characterization of Nigella sativa L. seed oil cultivated under the agro-climatic conditions of the Bukhara region of Uzbekistan and its comparison with data reported for other producing regions. The results demonstrate that, although the overall oil yield and fatty acid composition are comparable to those reported for seeds grown in Tajikistan, Egypt and Russia, the Bukhara samples exhibit a markedly higher accumulation of thymoquinone (2.3%). These findings indicate that the arid continental climate of the Bukhara region mainly influences secondary metabolite biosynthesis rather than primary lipid metabolism. In particular, the enhanced thymoquinone content represents a distinctive chemical feature of Bukhara-grown seeds and underlines their potential relevance for pharmaceutical and nutraceutical applications. Overall, the comparative evidence suggests that the Bukhara region represents a promising agro-ecological area for the cultivation of Nigella sativa with improved bioactive characteristics. Nevertheless, further studies involving controlled agronomic trials and genotype–environment interactions are required to confirm the stability of the observed chemical profile and to support future large-scale production and application.

Acknowledgements

The authors thank the staff of Bukhara State University for their assistance in laboratory analyses and data collection.

Data Availability Statement

The data supporting the findings of this study are available from the corresponding author upon reasonable request.

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Edited by

• Editor:
  Takako Matsumura Tundisi

Publication Dates

• Publication in this collection
  20 July 2026
• Date of issue
  2026

History

• Received
  15 Oct 2025
• Accepted
  13 Feb 2026