背景:基于核磁共振(NMR)的代谢谱已广泛用于食品和植物科学。尽管它的简单性和固有的可重复性,适当的预处理程序的确定极大地影响所获得的代谢谱。
目的:当前的研究代表了食用橄榄(OleaeuropaeaL.)的基于非靶向NMR的代谢谱分析的详细指南。
方法:选择来自不同地理起源的希腊Kalamon表橄榄作为参考材料。使用不同的溶剂和/或溶剂系统提取不同处理的样品。用高效薄层色谱(HPTLC)评价化学概况。评估了不同的氘代溶剂和样品浓度,以记录最佳质量的光谱。
结果:发现冻干食用橄榄的甲醇提取物中含有最具代表性的次生代谢产物,在较高的浓度下,也是。NMR分析的最佳氘代溶剂是甲醇-d4,而最终样品浓度应在10至15mg/mL的范围内。还使用多变量数据分析来估计和确认由样品的不同特征引起的变异和聚类。
结论:本研究的结果表明,在基于NMR光谱的任何广泛的代谢组学研究之前,需要进行彻底的计划和方法开发。在食用橄榄的情况下,预处理和样品制备阶段似乎会极大地影响代谢谱和光谱质量,通过推断可以适用于其他食品。然而,样品的性质必须全面描述,为了得出坚实的结论。
BACKGROUND: Nuclear magnetic resonance (NMR)-based metabolic profiling has been widely used in food and plant sciences. Despite its simplicity and inherent reproducibility, the determination of the appropriate pre-processing procedures greatly affects the obtained metabolic profile.
OBJECTIVE: The current study represents a detailed guide of use for untargeted NMR-based metabolic profiling of table olives (Olea europaea L.).
METHODS: Greek Kalamon table olives from different geographical origins were selected as reference materials. Differently treated samples were extracted using different solvents and/or solvent systems. Chemical profiles were evaluated with high-performance thin layer chromatography (HPTLC). Different deuterated solvents and sample concentrations were evaluated for the recording of optimal quality spectra.
RESULTS: The methanol extract of freeze-dried table olives was found to contain the most representative secondary metabolites, in higher concentrations, as well. The optimal deuterated solvent for the NMR analysis was methanol-d4 , while final sample concentration should be within the range of 10 to 15 mg/mL. Multivariate data analysis was also used to estimate and confirm the variation and clustering caused by different characteristics of the samples.
CONCLUSIONS: Results of the present study make evident the necessity for thorough planning and method development prior to any extensive metabolomic study based on NMR spectroscopy. Pre-processing and sample preparation stages seemed to greatly affect the metabolic profile and spectral quality in the
case of table olives, which by extrapolation could apply to other food commodities. Nevertheless, the nature of the samples must be fully described in general, in order to proceed to solid conclusions.