Targeted and Non-Targeted Analyses of Secondary Metabolites in Nut and Seed Processing

Drying enhances the antioxidant activity of Allium mongolicum Regel through the phenylpropane and AA-MA pathway as shown by metabolomics

Fresh Allium mongolicum Regel (FA) and dried A. mongolicum Regel (DA) are significantly different in antioxidant activity. However, the relevant mechanisms have not yet been explored. We evaluated the antioxidant activities of two varieties of FA and DA and characterized their metabolites using targeted metabolomics. The effect of different metabolites on the antioxidant activity of A. mongolicum Regel was investigated by multivariate analysis. A total of 713 metabolites were detected in all samples. Pearson correlation analysis demonstrated that the key primary metabolites were directly and significantly correlated with the total phenolic content (TPC) and total flavonoid content (TFC), while the secondary metabolites were directly correlated with antioxidant activity. The higher antioxidant activity of DA may be mainly attributed to the higher TPC and TFC. This study revealed the potential mechanism by which drying enhances the antioxidant activity of A. mongolicum Regel.

Breba Fruits Characterization from Four Varieties (Ficus carica L.) with Important Commercial Interest in Spain

Although most of the published articles generalize with the fruit of the fig tree (Ficus carica L.), the differentiation between fig and breba is increasingly common in the bibliography. In this regard, keep in mind that the fig tree generally produces two crops a year, the parthenocarpic breba, also called as early fig, and the main non-parthenocarpic crop, the fig proper. In this study, four brebas varieties (‘Colar’, ‘SuperFig1’, ‘Cuello de Dama Negro’ and ‘San Antonio’) were selected in order to identify compositional, nutritional, and chemical diversity. These varieties were chosen for their commercial relevance in Spain. Color (internal and external), fruit and peel weight, size, pH, total soluble solids (TSS), titratable acidity (TA), maturity index (MI), sugar, and organic content were determined for all the breba fruits samples. In addition, polyphenolic profile, amino acids, and volatile aromatic compounds were also identified. The varieties ‘Colar’ and ‘SuperFig1’ showed the highest fruit weight and size, while ‘Cuello de Dama Negro’ presented the higher pulp yield. The higher organic acid and sugar contents were determined for ‘SuperFig1’ and ‘Cuello de Dama Negro’, respectively. Although in low concentrations, the phenolic compound quercetin 3-(6-O-acetyl-beta-glucoside) and the amino acid tyrosine were only detected in the ‘’Cuello de Dama Negra’ and ‘SuperFig1’ fruits, respectively. Of the eighty volatile aromatic compounds identified, only eight were common in four varieties. An important knowledge gap was identified in relation to the characterization of the two Ficus carica L. crops, that is, the differentiation and specification in the literature when working with brebas and/or figs.

Experimental Design and Sample Preparation in Forest Tree Metabolomics

Appropriate experimental design and sample preparation are key steps in metabolomics experiments, highly influencing the biological interpretation of the results. The sample preparation workflow for plant metabolomics studies includes several steps before metabolite extraction and analysis. These include the optimization of laboratory procedures, which should be optimized for different plants and tissues. This is particularly the case for trees, whose tissues are complex matrices to work with due to the presence of several interferents, such as oleoresins, cellulose. A good experimental design, tree tissue harvest conditions, and sample preparation are crucial to ensure consistency and reproducibility of the metadata among datasets. In this review, we discuss the main challenges when setting up a forest tree metabolomics experiment for mass spectrometry (MS)-based analysis covering all technical aspects from the biological question formulation and experimental design to sample processing and metabolite extraction and data acquisition. We also highlight the importance of forest tree metadata standardization in metabolomics studies.