Universidade Federal do Rio Grande do Sul, Instituto de Química, Porto Alegre, RS, Brazil.
Universidade Federal de Minas Gerais, Instituto de Ciências Biológicas, Belo Horizonte, MG, Brazil.
Talanta. 2017 Dec 1;175:9-20. doi: 10.1016/j.talanta.2017.06.063. Epub 2017 Jun 27.
A headspace solid phase microextraction (HS-SPME) method combined with gas chromatography-mass spectrometry (GC/MS) was developed and optimized for extraction and analysis of volatile organic compounds (VOC) of leaves and galls of Myrcia splendens. Through a process of optimization of main factors affecting HS-SPME efficiency, the coating divivnilbenzene-carboxen-polydimethylsiloxane (DVB/Car/PDMS) was chosen as the optimum extraction phase, not only in terms of extraction efficiency, but also for its broader analyte coverage. Optimum extraction temperature was 30°C, while an extraction time of 15min provided the best compromise between extraction efficiencies of lower and higher molecular weight compounds. The optimized protocol was demonstrated to be capable of sampling plant material with high reproducibility, considering that most classes of analytes met the 20% RSD FDA criterion. The optimized method was employed for the analysis of three classes of M. splendens samples, generating a final list of 65 tentatively identified VOC, including alcohols, aldehydes, esters, ketones, phenol derivatives, as well as mono and sesquiterpenes. Significant differences were evident amongst the volatile profiles obtained from non-galled leaves (NGL) and leaf-folding galls (LFG) of M. splendens. Several differences pertaining to amounts of alcohols and aldehydes were detected between samples, particularly regarding quantities of green leaf volatiles (GLV). Alcohols represented about 14% of compounds detected in gall samples, whereas in non-galled samples, alcohol content was below 5%. Phenolic derived compounds were virtually absent in reference samples, while in non-galled leaves and galls their content ranged around 0.2% and 0.4%, respectively. Likewise, methyl salicylate, a well-known signal of plant distress, amounted for 1.2% of the sample content of galls, whereas it was only present in trace levels in reference samples. Chemometric analysis based on Heatmap associated with Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) provided a suitable tool to differentiate VOC profiles in vegetal material, and could open new perspectives and opportunities in agricultural and ecological studies for the detection and identification of herbivore-induced plant VOC emissions.
建立并优化了顶空固相微萃取（HS-SPME）与气相色谱-质谱联用（GC/MS）的方法，用于提取和分析美丽桃金娘叶片和虫瘿中的挥发性有机化合物（VOC）。通过对影响 HS-SPME 效率的主要因素进行优化的过程，选择了二乙烯基苯-羧基-聚二甲基硅氧烷（DVB/Car/PDMS）涂层作为最佳萃取相，不仅萃取效率高，而且分析物覆盖范围更广。最佳萃取温度为 30°C，而 15min 的萃取时间则在低分子量化合物和高分子量化合物的萃取效率之间提供了最佳折衷。考虑到大多数类别的分析物都符合 20%RSD FDA 标准，该优化方案证明能够对植物材料进行高重现性采样。该优化方法用于分析三种美丽桃金娘样品，最终确定了 65 种暂定鉴定的 VOC，包括醇类、醛类、酯类、酮类、酚类衍生物，以及单萜和倍半萜。非虫瘿叶（NGL）和叶折叠虫瘿（LFG）之间的挥发性特征存在显著差异。在样品之间检测到醇类和醛类的含量存在差异，特别是关于绿叶挥发物（GLV）的含量。在虫瘿样品中，醇类约占检测到化合物的 14%，而在非虫瘿样品中，醇类含量低于 5%。在参考样品中几乎不存在衍生自酚类的化合物，而在非虫瘿叶和虫瘿中，其含量分别约为 0.2%和 0.4%。同样，水杨酸甲酯是一种众所周知的植物应激信号物，在虫瘿样本中的含量占样品含量的 1.2%，而在参考样本中仅以痕量存在。基于热图与层次聚类分析（HCA）和主成分分析（PCA）相结合的化学计量学分析为区分植物材料中的 VOC 图谱提供了合适的工具，并且可以为农业和生态研究中检测和识别食草动物诱导的植物 VOC 排放开辟新的视角和机会。
