Characterization of Plant Volatiles Reveals Distinct Metabolic Profiles and Pathways among 12 Brassicaceae Vegetables  
[PERSON]  
1 NUS Environment Research Institute, National University of Singapore, Singapore 117411, Singapore; [EMAIL_ADDRESS] (Y.L. ); [EMAIL_ADDRESS] (H.Z. ); [EMAIL_ADDRESS] (S.U. ); [EMAIL_ADDRESS] (X.L. ); [EMAIL_ADDRESS] (H.W.L. ); [EMAIL_ADDRESS] (S.S.)  
[PERSON]  
1 NUS Environment Research Institute, National University of Singapore, Singapore 117411, Singapore; [EMAIL_ADDRESS] (Y.L. ); [EMAIL_ADDRESS] (H.Z. ); [EMAIL_ADDRESS] (S.U. ); [EMAIL_ADDRESS] (X.L. ); [EMAIL_ADDRESS] (H.W.L. ); [EMAIL_ADDRESS] (S.S.)  
[PERSON]  
1 NUS Environment Research Institute, National University of Singapore, Singapore 117411, Singapore; [EMAIL_ADDRESS] (Y.L. ); [EMAIL_ADDRESS] (H.Z. ); [EMAIL_ADDRESS] (S.U. ); [EMAIL_ADDRESS] (X.L. ); [EMAIL_ADDRESS] (H.W.L. ); [EMAIL_ADDRESS] (S.S.)  
[PERSON]  
1 NUS Environment Research Institute, National University of Singapore, Singapore 117411, Singapore; [EMAIL_ADDRESS] (Y.L. ); [EMAIL_ADDRESS] (H.Z. ); [EMAIL_ADDRESS] (S.U. ); [EMAIL_ADDRESS] (X.L. ); [EMAIL_ADDRESS] (H.W.L. ); [EMAIL_ADDRESS] (S.S.)  
Sanjay Swee Hock School of Public Health, National University of Singapore, Singapore 117549, Singapore  
the atmosphere or soil, allowing the plant to interact with its surroundings [2]. From a physiological standpoint, plant VOCs play important roles in plant-plant or within-plant signalling [3; 4], as well as providing protection by deterring herbivores or pathogens [5; 6], attracting natural enemies of herbivores [7], and enhancing resistance to plant damage or against abiotic stresses [8]. In addition, plant VOCs are major determinants of food flavour and aroma, which are of great agronomic importance for food quality [9; 10]. Recently, the findings of the beneficial effects of plant VOCs on human health also shed light on drug discovery [11]. Thus, plant VOCs, as a significant part of plant metabolome, are of particular interest to researchers in ecology, agriculture, food quality and safety, and functional food usage. Brassicaceae vegetables, also known as cruciferous vegetables, have attracted increasing research interest because they are among the most commonly consumed vegetables globally, and have been demonstrated to have substantial human health benefits [12]. Recent studies on VOCs emitted from Brassicaceae vegetables have been dedicated to characterizing the vegetables, identifying the aroma components, and evaluating the quality of vegetables, such as VOCs in watercress [13], radish [14], Korean cabbage [15], Brussels sprouts and cauliflower during blanching [16], Brussels sprouts damaged by caterpillars [17], broccoli under ambient and elevated atmospheric CO\({}_{2}\) concentrations [18] and rocket during the post-harvest storage [19]. However, most of these studies focused mainly on the fingerprint of VOCs in a single species, so there is still a lack of comprehensive comparison of VOCs profiles in commonly consumed Brassicaceae vegetables. As volatile metabolites in vegetables, VOCs are typical end products in the related metabolic pathways. For example, studies revealed that the glucosinolates (GLSs) in Brassicaceae vegetables could be enzymatically broken down to form isothiyanates (ITCs), which are typical vegetable VOCs [7; 20]. The VOCs profiles may reflect differences in metabolic pathways among various vegetables. In Brassicaceae vegetables, the correlation of VOCs and the possible metabolic pathways for the formation and emission of VOCs are yet to be systematically investigated. On the other hand, there has been significant progress in the methodologies and analytical instruments for precise and comprehensive investigation of plant VOCs. In the literature, various extraction methods have been developed for analysis of VOCs in plant, including liquid-liquid extraction [21], steam distillation or simultaneous distillation extraction [22], purge and trap, and headspace solid phase micro-extraction (HS-SPME) [23].