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Chemotaxonomic variation of volatile components in Zanthoxylum Bungeanum peel and effects of climate on volatile components

BMC Plant Biology volume 24, Article number: 793 (2024) Cite this article

Abstract

Background

Zanthoxylum bungeanum Maxim. is widely distributed across China, and the aroma of its peel is primarily determined by its volatile components. In this study, we analyzed the characteristics of volatile components in Z. bungeanum peels from different regions and investigated their correlation with climatic factors.

Results

The results identified 126 compounds in Z. bungeanum, with 27 compounds exhibiting distinct odor characteristics. Linalool was the most abundant, with an average relative content of 21.664%. The volatile oil of Z. bungeanum predominantly features spicy, floral, citrus, and mint aromas. The classification results indicated a significant difference in elevation at the ZB10 collection points in Shaanxi Province compared to other groups. Temperature, average annual precipitation, and wind speed were crucial factors influencing the accumulation of volatile components.

Conclusions

This study is beneficial for enhancing the quality of Z. bungeanum, expanding the understanding of how climatic factors influence the accumulation of volatile substances, and promoting agricultural practices in regions with similar climatic conditions.

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Introduction

Zanthoxylum bungeanum is one of China’s most important traditional condiments, with its primary edible and medicinal components found in the peels [1]. Due to its low environmental requirements and strong ecological adaptability, Z. bungeanum is widely cultivated across the country [2]. primarily in Sichuan, Yunnan, Guizhou, Chongqing, Shaanxi, Gansu, and other regions. The harvest season is from June to August each year. Renowned for its unique flavor, Z. bungeanum is considered an indispensable seasoning in Chinese cuisine and is extensively used in food processing. Z. bungeanum is rich in bioactive compounds [3], including alkaloids [4], volatile oils [5], amides [6]and phenols [7]. Its distinctive odors [8] is primarily determined by the volatile components in the peel [9, 10]. Volatile oils, synthesized by defense- and reproduction-related organs in aromatic plants [11], consist of complex mixtures of dozens to several hundred substances with varying concentrations [12, 13]. Typically, two or three of these are the main components at concentrations greater than 30%, while the others are present only at trace levels [14]. The most common components are monoterpenes, sesquiterpenes, and their oxygen-containing derivatives, though some trace components also play an indispensable role.

Gas chromatograph-mass spectrometer (HS-SPME-GC-O-MS) are two key methods for the analyzing and identifying volatile compounds [15,16,17]. These volatile compounds generally include terpene hydrocarbons (e.g., d-Limonene, α-Pinene, β-Myrcene, γ-Terpinolene, α-Thujene, and α-Cubebene), alcohols (e.g., β-Terpineol, Linalool, and Citronellol), aldehydes (e.g., Octanal, nonanal, Citronellal, Decanal, and Geranial), ketones (e.g., Cyclohexanone, Nootkatone, Pulegone, Verbenone, and (-)-Carvone), oxides (e.g., Caryophyllene oxide, (Z)-Limonene oxide, and (E)-Limonene oxide), esters (e.g., Neryl acetate and Geranyl acetate), and others (e.g., Toluene and Ethylbenzene) [18]. In this study, the volatile oils identified included d-Limonene, Linalool, Geranyl acetate, α-Pinene, α-Phellandren, and (Z)-3, 7-Dimethyl-2, 6-Octadien-1-ol, which are responsible for the characteristic fragrance of Sichuan pepper [19]. The difference in characteristic aroma substances of Z. bungeanum from different producing areas were analyzed using both qualitative and quantitative methods. Beyond being sources of aroma, volatile substances are key indicators of the essential quality of Z. bungeanum. The essential oil of Z. bungeanum has demonstrated anti-tumor, anti-inflammation, anti-itching, and other pharmacological activities, highlighting its value and potential in various applications [20,21,22]. In addition to its widespread use in spices, cooking, and as an antioxidant, Z. bungeanum extract has shown diverse benefits, including antibacterial, antiviral, peeling, weeding, medicinal transdermal, and lipid-lowering effects. It plays a crucial role in the food, cosmetics, pharmaceutical, and agricultural industries, offering extensive application prospects [9, 23,24,25]. Moreover, Z. bungeanum not only protects soil and conserves water but also increases farmers’ incomes and improves livelihoods, It is integral to significant projects such as “returning farmland to forest” and the transformation of rural industrial structures, demonstrating its substantial potential for sustainable development and rural revitalization.

The formation of plant secondary metabolites is closely related to plant growth and development [26, 27] and is strongly regulated by environmental factors such as precipitation, temperature, humidity, and soil [28]. The accumulation of active substances in plants is influenced by various factors, including plant characteristics, growth stage, seasonal changes, light intensity, altitude, climate conditions, and soil environment. Studies have shown that the physiological and ecological changes, as well as the genetic background of plants, can affect the quality and quantity of secondary metabolites, thereby influencing their biological activities [29, 30]. Altitude, precipitation, and soil texture are key factors affecting the composition of Z. bungeanum [31]. Altitude directly impacts temperature, precipitation, sunshine hours, and humidity, all of which influence plant growth and the accumulation of secondary metabolites [32,33,34]. In high-altitude areas, latitude and longitude significantly affect temperature and precipitation, thereby indirectly impacting the growth environment of medicinal plants. Consequently, latitude and longitude play crucial roles in these regions and significantly influence the growth of medicinal plants [35]. The production and accumulation of secondary metabolites in plants are influenced by various climate conditions, as these metabolites help plants cope with climate stress and provide adaptive advantages. Thus, during plant growth and development, the type, content, and proportion of secondary metabolites may be regulated by a variety of climatic factors, in addition to genetic factors [26, 36]. In recent years, diverse climatic and soil conditions have significantly impacted the growth and quality of food and medicinal plants, such as Ferula assa-foetida, Brassica oleracea, Vaccinium myrtillus, and Curcuma longa. Research has been conducted on the impact of different geographical locations on the content of secondary metabolites in plants like Eucommia ulmoides and Sinopodophyllum hexandrum [28, 36, 37]. The types and contents of volatile components in Z. bungeanum vary across different habitats and exhibit distinct morphological characteristics under varying climatic conditions. Therefore, studying the influence of climatic factors on the accumulation of volatile substances in Z. bungeanum peel is of great significance for the identification and targeted application of Z. bungeanum peel.

In the present study, ten samples of Z. bungeanum peels were collected from different regions of China, along with corresponding climatic data. The content and characteristics of volatile oil in Z. bungeanum peel were analyzed using ultra-high-performance liquid chromatography and mass spectrometry, combined with multivariate statistical methods, including hierarchical cluster analysis, principal component analysis, correlation analysis, and path analysis. The correlation between volatile oil compounds and climatic factors was examined. These results provide a deeper understanding of the effects of climatic factors on the quantity and quality of volatile compounds in Z. bungeanum peel, reveal regional differences in volatile oil composition across the natural distribution areas of Z. bungeanum,and identify key environmental factors affecting the accumulation of these compounds. This study offers a theoretical and practical foundation for quality evaluation, quality classification, and product source traceability of Z. bungeanum peels.

Materials and methods

Materials

Z. bungeanum samples were collected through local forestry bureaus or zanthoxylum planting companies. Z. bungeanum (Fig. 1) was gathered from ten sites at different altitudes (457–2450 m) across three provinces in China between July and September 2022. The collected fruits were deseeded and dried to obtain dried Z. bungeanum peel with a moisture content of less than 10.5%, with a sampling volume of 5–10 kg. The dried peel was then crushed, passed through a 60-mesh sieve, and stored in a refrigerator at -20℃ for future use. All experiments were repeated three times. All the specimens were authenticated by Professor Xu Danping of China West Normal University and stored in the School of Life Sciences, China West Normal University.

Fig. 1
figure 1

Map of samples collection sites

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The origin information of Z. bungeanum samples is shown in Table 1.

Table 1 Sample source information of Z. Bungeanum
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Sample preparations

The volatile oil was extracted from the dried and crushed Z. bungeanum peels using the HS-SPME method. The powdered sample of 1.5 g was transferred into a 10 mL headspace bottle, equilibrated at 80℃ for 30 min, and extracted by a solid-phase micro-extraction needle (100 μm PDMS fiber, SUPELCO, USA). After extraction, GC-MS analysis was performed by desorption at the inlet for 5 min. All experiments were repeated three times.

GC/MS conditions

An appropriate amount of volatile oil was diluted 40 times with methanol and filtered through a 0.22 μm filter membrane. Subsequently, 1 mL of the filtered solution was transferred into an automatic sampling vial. For GC-MS analysis, 1 µL of the sample was injected into an HP-5MS elastic quartz capillary column (30 m × 0.25 mm, 0.25 μm). Elastic quartz capillary column. The heating procedure is that the column temperature is 50℃ (reserved for 1 min), and it is raised to 75℃ at 1 min. Hold it for 1 min and then rise to 120℃ at 6 ℃/ min. Hold it for 1 min, and then rise to 135℃ at 1 min. For 1 min, the temperature rises to 200℃ at 15℃/ min and maintains it for 5 min [38]. Helium was employed as the carrier gas at a flow rate of 1.0 mL/ min, with a purge flow rate of 3 mL/ min. The inlet temperature was set to 250℃ and maintained at a pressure of 7.6522 psi.

The ion source utilized electron impact (EI) ionization at 70 eV, with an ion source temperature of 230℃, quadrupole temperature up to 200℃, and interface temperature of 280℃. Mass scanning was conducted over the range of 50 to 550 amu.

Volatile components were characterized by matching unknown compounds to the NIST 11 library, confirming identification with a match score above 80 (maximum 100). Retention indices (RI) of compounds were calculated using C6 to C20 and verified against literature reports [39].

For determination of main flavor components [40], the Relative Odor Activity Value (ROAV) method was employed to assess each volatile component’s contribution to Z. bungeanum flavor. The component contributing the most to the flavor was assigned an ROAV value of 100, with other components calculated relative to this standard using the prescribed formula.

$$\:{\text{R}\text{O}\text{A}\text{V}}_{\text{i}}=100\times\:\frac{{C}_{i}}{{C}_{stan}}\times\:\frac{{T}_{stan}}{{T}_{i}}$$

Among them, Ci and Cstan represent the relative content (%) of each volatile component and the component that contributes the most to the flavor, respectively. Ti and Tstan denote the odor thresholds (µg/kg) of each volatile component and the component that contributes the most to the flavor, respectively.

Statistical analysis

In this study, the relationship between Z. bungeanum and climate factors was analyzed. The data on average annual temperature (XAMT), average maximum temperature (XAMAT), average annual minimum temperature (XAMIT), annual relative humidity (XRH), average wind speed (XMW), maximum wind speed (XMAW), extreme wind speed (XEW), annual sunshine duration (XASD), and average annual precipitation (XAAP) in the sampling areas were obtained from the Meteorological Bureau. These climate factors are detailed in Table S1. Cluster and principal component analyses were conducted on Z. bungeanum samples from different origins based on the relative content of the main flavor substances. Statistical analysis and calculations were performed using Origin 2021 for generating hierarchical cluster analysis, principal component analysis, and correlation analysis charts. Additionally, SPSS 24.0 software was utilized for hierarchical cluster analysis, correlation analysis, regression analysis, and path analysis (IBM SPSS Statistics 27). Each sample was processed three times to ensure reliability and consistency of the results.

Results

Quantitative study of volatile components in Z. Bungeanum peel

The volatile components of 10 populations of Z. bungeanum were analyzed using gas chromatography-mass spectrometry (GC-MS), revealing a total of 126 detected compounds, detailed in Table S2. The total ion chromatogram is shown in Fig. 2. Variations in volatile components were primarily influenced by the content and types of olefins, alcohols, and esters. Terpenes were the most abundant group, comprising 63 different compounds, followed by alcohols (30) and esters (15). Terpenes exhibited the highest average relative content, followed by alcohols and esters. Among the alcohols identified in the volatile oil, terpenoids were predominant, with Linalool being the most significant terpene, averaging 23.13% relative content.

Fig. 2
figure 2

Comparison of total ion flow (B) and total ion current diagram (A) of Z. bungeanum volatile oil detected by GC-MS

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In Z. bungeanum, compounds with notably high average relative content include d-Limonene (24.71%) and Linalool (23.13%). The abundance of these compounds varied among samples, with d-Limonene and Linalool showing comparable relative contents in most samples except ZB3 and ZB6. In ZB3 and ZB6, the relative content of Linalool was 2.3 and 3.1 times higher than that of d-Limonene, respectively, Notably, ZB10 from Hancheng, Shaanxi Province, exhibited significantly different volatile components compared to other samples, with Limonene being the predominant compound at a relative content of 15.95%.

The 10 predominant components of Z. bungeanum from various main producing areas, along with their average relative contents, are as follows: d-Limonene (24.71%), Linalool (23.13%), Terpinen-4-ol (3.79%), trans-β-Ocimene (2.57%), Terpinolene (1.28%), Terpinyl acetate (1.11%), Germacrene D (1.03%), Alloocimene (0.86%), (Z)-3,7-Dimethyl-2,6-octadien-1-ol (0.44%), and γ-Elemene (0.29%). Among these, seven compounds have a relative content exceeding 1%.

Figure 3 illustrates significant differences in the content of various substances across the 10 samples. In Fig. 3(A), ZB8 exhibits the highest ester content at 14.77%, followed by ZB5 at 14.03% and ZB7 at 12.91%. Figure 3(B) shows that only ZB1, ZB4, ZB5, ZB7, ZB8, and ZB9 contain ethers, all with contents below 0.2%. Regarding ketones (Fig. 3(C)), ZB10 shows the highest content at 1.13%, while other samples range from 0.04 to 0.7%, except for ZB9. Figure 3(D) indicates that terpenes contribute the most to the volatile components of the peel. ZB1 and ZB10 exhibit the highest terpene contents, reaching 72.93% and 78.10%, respectively, followed by ZB2 (69.37%), ZB4 (66.83%), ZB9 (60.27%), and ZB3 (39.91%), which has the lowest terpene content. In ZB6, alcohols constitute 56.55% of the volatile components, with ZB3 following at 48.11%.

Fig. 3
figure 3

Relative contents of different types of compounds in volatile oil from different origins (%). A, esters; B, ethers; C, ketones; D, terpene and alcohols

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Analysis of common volatile characteristic components of Z. Bungeanum peel

The aroma and quality of Z. bungeanum peel predominantly depend on the content and composition of its volatile oil. In the study, the aroma profile of the volatile oil was characterized using GC-MS. Among all detected volatile oils, 27 compounds were identified as having distinct odor signatures, as outlined in Table S3. Terpenes were the most prevalent group, comprising 11 compounds, followed by 8 alcohols, 5 lipids, 2 ketones, and 1 aldehyde.

Among the 27 volatile substances identified, 18 were confirmed to have aroma-active properties through GC-O analysis, indicating that not all volatile substances contribute to aroma formation. Increasing the content of volatile compounds such as Terpinen-4-ol and Linalyl acetate may not necessarily enhance aroma formation. Conversely, compounds with lower concentrations such as α-Pinene, α-Phellandren, and (Z)-3,7-Dimethyl-2,6-Octadien-1-ol contribute significantly to the aroma profile. Both d-Limonene and Linalool exhibit distinctive odor characteristics and are among the most abundant compounds in Z. bungeanum. They are speculated to play crucial roles in determining the fragrance of Z. bungeanum.

The highest relative content of linalool in Z. bungeanum and the lower odor threshold (7.4 µg/kg) contributed the most to the flavorthus defining ROAVstan = 100 for Linalool. Based on the odor threshold and relative content data from Schedule S3, Table 2 presents the Relative Odor Activity Values (ROAV) for various compounds. Higher ROAV values indicate greater contributions to the overall flavor profile of the sample. Compounds with ROAV values above 1 are classified as key flavor compounds, while those with ROAV values between 0.1 and 1 significantly modify the overall flavor. Key flavor substances of Z. bungeanum identified include Linalool, Geranyl acetate, d-Limonene, β-Pinene, and Limonene, all with ROAV values exceeding 1. Additionally, there are 12 main flavor substances such as α-Copaene, Copaene, Caryophyllene, α-Terpineol, (R)-3,7-dimethyl-6-octenal, Terpinolene, and L-α-Terpineol contributing to the predominant fragrances of Z. bungeanum, characterized by oriental, floral, citrus, and minty notes. This study observed higher concentrations of key aroma substances like Limonene and Linalool in Z. bungeanum from northwest and southwest regions, enhancing the citrus aroma profile of peppers from these areas. According to Table S4, the difference of 12 substances was significant.

Table 2 The ROAV value of volatile components in Z. Bungeanum
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HCA and PCA analysis

Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were employed to analyze Z. bungeanum, focusing on 12 common volatile compounds (Linalool, Geranyl acetate, d-Limonene, β-Pinene, Limonene, α-Copaene, Copaene, Caryophyllene, α-Terpineol, (R)-3,7-Dimethyl-6-octenal, Terpinolene, and L-α-Terpineol) with ROAV values above 0.1. These compounds were selected for correlation analysis, as depicted in Fig. 4. HCA was used to cluster the samples based on their volatile profiles, utilizing Pearson correlation as the measurement criterion. The Z-score method was applied to standardize the relevant variables, resulting in the creation of the cluster plot.

The results of hierarchical cluster analysis (HCA) are depicted in Fig. 5. At a distance coefficient of 0.4, the 10 Z. bungeanum samples can be grouped into two clusters. With a distance coefficient of 0.15, the samples can be further divided into three distinct groups. Specifically, samples ZB1, ZB2, ZB4, ZB5, ZB7, ZB8, and ZB9 cluster together, while samples ZB10 form a separate group due to their collection in Shaanxi Province at lower altitudes. Samples ZB3 and ZB6 also cluster together based on their geographical similarities. Notably, ZB10 stands out with a significant difference in its volatile profile, particularly characterized by a high content of Limonene. Samples ZB5, ZB7, ZB8, and ZB9 share similarities and are clustered together, collected from altitudes ranging between 1000 and 2000 m. Similarly, ZB1 and ZB4 form another distinct group, collected at altitudes exceeding 2000 m in Sichuan Province. These findings underscore the close relationship between the relative content of characteristic aroma substances and the geographic origin of Z. bungeanum. The study highlights the comprehensive impact of climate factors on secondary metabolites, reflecting geographic continuity across different classes of secondary metabolites.

In the principal component analysis (PCA) shown in Fig. 6, two principal components (PC1 and PC2) were constructed, explaining variance rates of 31.9% and 25.7%, respectively. The 3D scoring plot of PCA (Fig. 7) illustrates a trend where the samples are separated into relatively distinct groups. Consistently, the 10 samples can be categorized into 2 main groups, which aligns with the clustering observed in the hierarchical cluster analysis (HCA).

Consistent with the cluster analysis results, sample ZB10 exhibits a significant distance from other samples on the principal component scatter plot. This indicates that the flavor profile of ZB10 from Hancheng, Shaanxi Province, is notably distinct from the others. Limonene is identified as the key flavor compound that differentiates ZB10 from the rest. In contrast, samples ZB3 and ZB6 are clustered closely together on the principal component score chart and are distinctly separate from the other samples. Caryophyllene emerges as the characteristic flavor substance associated with these two samples.

Fig. 4
figure 4

The relative content of common volatile components in Z. bungeanum samples. Yβ-PI, β-Pinene; YCO, Copaene; YLIM, Limonene; Yd-LIM, d-Limonene; YTE, Terpinolene; YCAR, Caryophyllene; YLIN, Linalool; YL-α-TE, L-α-Terpineol; Yα-TE, α-Terpineol; YGE, Geranyl acetate; Y(R)-3,7-DI, (R)-3,7-Dimethyl-6-octenal; Yα-CO, α-Copaene

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Fig. 5
figure 5

Dendrograms resulting from hierarchical clustering analysis of Z. bungeanum from different locations

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Fig. 6
figure 6

2-D scores plot of the PCA of 10 samples

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Fig. 7
figure 7

loading values of PCA of all 10 common characteristic volatile components on 3-D map

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Correlation analysis between climate factors and volatile components of Z. Bungeanum

Correlation analysis

The production and accumulation of volatile oil in Z. bungeanum peel across different regions are influenced by various climate factors. Twelve common volatile compounds (Linalool, Geranyl acetate, d-Limonene, β-Pinene, Limonene, α-Copaene, Copaene, Caryophyllene, α-Terpineol, (R)-3,7-Dimethyl-6-octenal, Terpinolene, and L-α-Terpineol), each with an ROAV value greater than 0.1, were selected for correlation analysis with climate factors. The results of the correlation analysis (Fig. 8 and Table S5) reveal varying degrees of association between these compounds and climate variables. When categorizing all climate factors into two clusters, XAMT, XAMAT, XASD, and XMW form one cluster, while XAMIT, XAAP, and XRH form another. Specifically, Terpinolene, β-Pinene, Limonene, d-Limonene, Caryophyllene, α-Copaene, and Copaene exhibit positive correlations with XAMAT, XAMIT, and XAMT, indicating that higher temperatures promote the formation of terpenes. In contrast, Linalool, L-α-Terpineol, and α-Terpineol show negative correlations with XAMT, XAMIT, and XAMAT, suggesting that high temperatures and temperature fluctuations are unfavorable for the accumulation of alcohols. Additionally, β-Pinene, α-Copaene, Linalool, L-α-Terpineol, and Geranyl acetate are negatively correlated with XASD, indicating that reduced sunshine duration affects their accumulation. Limonene, Copaene, and (R)-3,7-Dimethyl-6-octenal are significantly positively correlated with XMW. suggesting that higher wind speeds promote the accumulation of these compounds. On the other hand, Linalool, Geranyl acetate, and L-α-Terpineol show positive correlations with XAAP and XRH, while being negatively correlated with XAMT, indicating that cooler temperatures and ample precipitation favor their accumulation, Furthermore, β-Pinene, d-Limonene, and α-Copaene exhibit significant positive correlations with XAAP and XRH, suggesting that increased precipitation promotes the accumulation of these compounds.

Fig. 8
figure 8

Correlation analysis results of environmental factors and volatile components of Z. bungeanum peels. XMW (m/s), wind speed; XASD (h), Annual sunshine duration; XAMIT (℃), minimum temperature; XAMT (℃), average temperature; XAAP (mm), Rainfall data; XRH (%), medial humidity; XAMAT (℃), highest temperature; Yβ-PI, β-Pinene; YCO, Copaene; YLIM, Limonene; Yd-LIM, d-Limonene; YTE, Terpinolene; YCAR, Caryophyllene; YLIN, Linalool; YL-α-TE, L-α-Terpineol; Yα-TE, α-Terpineol; YGE, Geranyl acetate; Y(R)-3,7-DI, (R)-3,7-Dimethyl-6-octenal; Yα-CO, α-Copaene

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Path analysis

Path analysis (PA) was employed to assess both the direct and indirect effects of climate factors on volatile components in Z. bungeanum peels (Table 3). Specifically, 12 common volatile compounds were selected as independent variables, while climate factors were designated as dependent variables. The analysis proceeded through several steps: Initially, climate factors and volatile components were subjected to stepwise regression analysis using SPSS statistical software. Subsequently, based on the regression results, the primary climate factors influencing each compound were identified. Finally, path coefficients, representing both direct and indirect effects, were calculated to elucidate the relationships between climate factors and volatile compounds.

XMW was significantly positively correlated with Copaene and (R)-3,7-Dimethyl-6-octenal (P < 0.001). XMW is a key factor affecting Limonene (1.071), Copaene (0.886), and (R)-3,7-Dimethyl-6-octenal (1.071). XAMT had positive direct and indirect effects on limonene and (R)-3,7-Dimethyl-6-octenal, but negative direct and indirect effects on Geranyl acetate. The direct effect of XAMIT on Terpinolene (-0.695) was negative (P < 0.05), and the direct effect of XAAP on α-Copaene (0.644) was positive (P < 0.05). The positive correlation coefficient of XMW to Limonene was the largest (0.988), indicating that XMW was the main reason affecting Limonene. The direct effects of XASD and XAAP on Limonene and (R)-3,7-Dimethyl-6-octenal are negative, and the indirect effects are positive. XAAP is a key factor affecting α-Copaene and has a positive direct effect (0.644). XAMT is a key factor influencing Geranyl acetate with a negative direct effect (-0.632). In conclusion, path analysis elucidates the relative importance of each climatic factor on volatile components, enhancing the reasonableness of multivariate statistical analysis. The results demonstrated that temperature, rainfall data, and average wind speed significantly influenced the contents of individual volatile oils and total volatile oils.

Table 3 Path analysis between climate factors and volatile component of 6 Z. bungeanum peels
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Discussion

The production and accumulation of secondary metabolites are influenced by a multitude of factors, including internal factors such as genetic inheritance, tree age, and seasonal variations, as well as external ecological conditions such as light, temperature, and precipitation. Plants from different provenances exhibit variations even in the same environmental conditions, and these factors collectively impact the synthesis and accumulation of secondary metabolites [44]. Different environmental conditions across various production areas result in varying levels of active ingredients in plants. Significant differences in volatile compound contents were observed among 10 natural habitat samples of Z. bungeanum, with a total of 126 compounds detected, predominantly terpenes and terpene alcohols. Terpenoids are primary secondary metabolites in plants and play a crucial role in aroma production [45]. Among individual compounds, Linalool and d-Limonene exhibited the highest average relative content in Z. bungeanum. The contribution of terpenes to the volatile components of Z. bungeanum peel was most pronounced in ZB1 (72.93%) and ZB10 (78.10%). The sample ZB6 had the highest relative content of alcohols (56.55%), while ZB8 showed the highest content of esters (14.77%).

Among the 27 common volatile substances, d-Limonene imparts fresh citrus and minty notes; Linalool contributes sweet floral notes reminiscent of lavender and rosemary; and Geranyl acetate adds hints of rose, bergamot, and lavender. The volatile oil of Z. bungeanum is characterized by fragrant, floral, citrus, and minty aromas. Key flavor substances in Z. bungeanum include Linalool, d-Limonene, Geranyl acetate, Caryophyllene, α-Copaene, These compounds likely play a significant role in defining the distinctive flavor profile of Z. bungeanum [46].

Furthermore, variations in volatile substance content occur within the same variety due to different growing environments. For instance, ZB1, ZB7, and ZB10 belong to the same variety of Z. bungeanum, but their growth environments differ in climate factors, leading to significant differences in volatile component content, This suggests that climate factors may contribute to variations in volatile content. The flavor of Z. bungeanum samples from Hancheng City, Weinan City, and Shaanxi Province notably differs from other samples of Z. bungeanum, likely influenced by factors such as variety, environmental conditions, and human activities [47].

The PCA and HCA analyses revealed significant variations in volatile substances across different habitats. β-Pinene, Limonene, and Linalool emerged as potential key compounds for distinguishing Z. bungeanum from various origins. These compounds can serve as markers for differentiating origins and are valuable for the quality assessment of Z. bungeanum peel.

Climatic factors such as temperature, precipitation, relative humidity, wind speed, and annual sunshine duration can influence the production and accumulation of plant secondary metabolites [48]. Studies conducted by Olha Mykhailenko and her team have demonstrated that sunshine duration positively affects the accumulation of phenolic compounds in iris flowers [49]. Furthermore, it has been observed that temperature and water vapor pressure exhibit a significant negative correlation with flavonoid content in iris, whereas wind speed shows a significant positive correlation with flavonoid content [50].

In this study, the relationship between 12 common characteristic volatile substances and climate factors varies significantly. Higher temperatures correlate with increased levels of β-Pinene, Limonene, d-Limonene, Caryophyllene, Alpha-copaene, and Copaene. Conversely, lower temperatures and minimal temperature fluctuations favor the formation of Linalool, L-α-Terpineol, and α-Terpineol. Conditions of low temperatures coupled with ample precipitation are conducive to the accumulation of Linalool, Geranyl acetate, and L-α-Terpineol. Adequate precipitation also promotes the accumulation of β-Pinene, d-Limonene, and α-Copaene. Within the same environment, d-Limonene, α-Terpineol, L-α-Terpineol, Linalool, Caryophyllene, Terpinolene, α-Phellandren, and Geranyl acetate are more sensitive to environmental stress, whereas the content of β-pinene and Limonene is less influenced by climatic factors. By manipulating climate conditions, we can study the regulatory effects of volatile substances in Z. bungeanum and further investigate the mechanisms underlying the synthesis and accumulation of volatile oil under varied ecological conditions. Understanding these processes through molecular biology technologies could potentially enhance the quality of Z. bungeanum peel. Therefore, exploring the regulatory effects of climate factors on volatile substances in Z. bungeanum peel offers valuable insights into the ecological responses underlying the accumulation of volatile oil.

Conclusion

Environmental factors play a crucial role in shaping the accumulation of secondary metabolites. This study utilized GC-MS to analyze and identify aromatic compounds in Z. bungeanum from ten distinct regions, investigating their relationship with climatic variables. The volatile oil composition of wild Z. bungeanum exhibited significant regional variation, with terpenes predominating. Notably, d-Limonene (24.71%) and Linalool (23.13%) were identified as compounds with relatively high average contents in Z. bungeanum. Relative Odor Activity Value (ROAV) analysis highlighted d-Limonene and Linalool as key aroma compounds, imparting a robust citrus aroma to peppers from these regions.Correlation and path analyses of volatile components and ecological factors revealed that temperature, rainfall patterns, and average wind speed exert substantial influences on the accumulation of volatile oil compounds. This study not only establishes a foundation for identifying superior Z. bungeanum resources based on volatile compound profiles but also provides comprehensive insights and valuable references regarding the impact of climatic factors on the accumulation of volatile substances in Z. bungeanum.

Data availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

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This research was funded by the Sichuan Province Science and Technology (2022NSFSC0986), China West Normal University (20A007, 20E051, 21E040 and 22kA011).

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  1. Yuhan Wu and Zhihang Zhuo are contributed equally to this work and should be considered co-first authors.

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  1. College of Life Science, China West Normal University, Nanchong, 637002, China

    Yuhan Wu, Zhihang Zhuo, Qianqian Qian & Danping Xu

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Conceptualization, Zhihang Zhuo; methodology, Yuhan Wu and Danping Xu; software, Danping Xu and Yuhan Wu; formal analysis, Yuhan Wu and Zhihang Zhuo; investigation, Qian Qianqian; data curation, Qian Qianqian; writing-original draft preparation, Yuhan Wu; writing-review and editing, Danping Xu and Zhihang Zhuo; supervision, Zhihang Zhuo.

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Wu, Y., Zhuo, Z., Qian, Q. et al. Chemotaxonomic variation of volatile components in Zanthoxylum Bungeanum peel and effects of climate on volatile components. BMC Plant Biol 24, 793 (2024). https://doi.org/10.1186/s12870-024-05485-8

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BMC Plant Biology

ISSN: 1471-2229

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