Characterization of Plant Volatiles Reveals Distinct Metabolic Profiles and Pathways among 12 Brassicaceae Vegetables

Abstract

Plants emit characteristic organic volatile compounds (VOCs) with diverse biological/ecological functions. However, the links between plant species/varieties and their phytochemical emission profiles remain elusive. Here, we developed a direct headspace solid-phase microextraction (HS-SPME) technique and combined with non-targeted gas chromatography‒high-resolution mass spectrometry (GC-HRMS) platform to investigate the VOCs profiles of 12 common Brassicaceae vegetables (watercress, rocket, Brussels sprouts, broccoli, kai lan, choy sum, pak choi, cabbage, Chinese cabbage, cauliflower, radish and cherry radish). The direct HS-SPME sampling approach enabled reproducible capture of the rapid-emitting VOCs upon plant tissue disruption. The results revealed extensive variation in VOCs profiles among the 12 Brassicaceae vegetables. Furthermore, principal component analysis (PCA) showed that the VOC profiles could clearly distinguish the 12 Brassicaceae vegetables, and that these profiles well reflected the classical morphological classification. After multivariate statistical analysis, 44 VOCs with significant differences among the Brassicaceae vegetables were identified. Pathway analysis showed that three secondary metabolism pathways, including the fatty acid pathway, methylerythritol phosphate (MEP) pathway and glucosinolate (GLS) pathway, behave distinctively in these vegetables. These three pathways are responsible for the generation and emission of green leaf volatiles (GLVs), terpenes and isothiocyanates (ITCs), respectively. Correlation analysis further showed that volatile metabolites formed via the common pathway had significantly positive correlations, whereas metabolites from different pathways had either non-significant or significantly negative correlations. Genetic influences on these metabolites across various vegetable types were also evaluated. These findings extend our phytochemical knowledge of the 12 edible Brassicaceae vegetables and provide useful information on their secondary metabolism.

An Integrated Metabolomics Study of Glucosinolate Metabolism in Different Brassicaceae Genera

“…The results from our principal component analysis (PCA) analysis of the 12 vegetables studied ( Figure 2 ) agreed well with the results from our previous studies [ 30 , 48 ]. In the present study, we are able to distinguish the same 12 vegetables using PCA, based on the profiles of volatile compounds [ 48 ] and glucosinolates [ 30 ]. For volatile organic compounds, 1490 features were subjected to PCA after cleaning the data of features present in blanks and with too low detection frequencies, with the vegetable samples separated into 12 clusters that correspond to each genus.…”

Oviposition Preference of the Cabbage Root Fly towards Some Chinese Cabbage Cultivars: A Search for Future Trap Crop Candidates

“…There is a higher concentration of AITC in the volatile profile of broccoli and chinensis than in pekinensis, while the concentration of HA is higher in the broccoli profile than in either chinensis or pekinensis [56]. DMDS reduces D. radicum oviposition when released at high concentration in the environment [57] and broccoli emits greater quantities of it compared to pekinensis or chinensis [56]. Together, these differences might explain the oviposition differences found between our three subspecies, however, data are still lacking regarding the variability of VOC profiles among the cultivars we used.…”

“…AITC attracts females at low concentrations but becomes repellent at higher ones while HA is never attractive and also becomes repellent at high concentrations [54,55]. There is a higher concentration of AITC in the volatile profile of broccoli and chinensis than in pekinensis, while the concentration of HA is higher in the broccoli profile than in either chinensis or pekinensis [56]. DMDS reduces D. radicum oviposition when released at high concentration in the environment [57] and broccoli emits greater quantities of it compared to pekinensis or chinensis [56].…”

Volatile Organic Compounds (VOCs) of Endophytic Fungi Growing on Extracts of the Host, Horseradish (Armoracia rusticana)

“…There are several studies published on VOCs from Brassicaceae vegetables, but these exclusively use the plant myrosinase as the decomposing agent. Usually, the headspace-SPME approach is used [26,27], with some sort of GC-MS detection. The major disadvantages of SPME fibers are ageing of the fiber material, selectivity of the adsorption of volatiles onto the fiber, and possible saturation effects resulting in carry-over.…”

“…The major disadvantages of SPME fibers are ageing of the fiber material, selectivity of the adsorption of volatiles onto the fiber, and possible saturation effects resulting in carry-over. Despite these, this technique is widely used for the screening of volatiles due to its sensitivity, but it is rather used in a semi-quantitative fashion, also reflected in the studies [26,27]. For some analytes, however, much higher sensitivity can be obtained using a proper fiber than by injecting headspace air.…”