Browsing by Subject "Phenolics"

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    Chemometric approach for profiling of metabolites of potential antioxidant activity in Apiaceae species based on LC-PDA-ESI-MS/MS and FT-NIR
    (2023) Atta, Noha H.; Handoussa, Heba; Klaiber, Iris; Hitzmann, Bernd; Hanafi, Rasha S.
    Chemometrics is a tool for data mining and unlocking the door for solving big data queries. Apiaceae is a family species which is commonly cultivated worldwide. Although members of this species are widely used as antioxidant, antibacterial, antifungal, and anti-inflammatory agents, their metabolites profiling remains ambiguous. Based on WHO support, chemometrics has been used in evaluating the quality and authenticity of the herbal products. The objective of this study is to profile and characterize phenolic metabolites in nine species from Egyptian cultivars and three different species of German cultivars from the Apiaceae family using multivariate analysis after LC-PDA-ESI-MS/MS and near infrared spectroscopy data are generated. Principal component analysis was successfully applied to distinguish between the nine Egyptian cultivars and the three German cultivars, and hierarchical cluster analysis also confirmed this distinctive clustering. Partial least square regression (PLS-R) models showed a relationship between phytochemicals and antioxidant activities. The metabolites responsible for the clustering pattern and variables important for projection (VIP) were identified, being twelve amongst nine Egyptian cultivar samples and thirteen amongst the Egyptian cultivar and the German cultivar comparison. The identified VIPs were also correlated with the antioxidant activity using PLS-R. In conclusion, the study showed novelty in the application of hyphenated analytical techniques and chemometrics that assist in quality control of herbal medicine.
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    Root exudate fingerprint of Brachiaria humidicola reveals vanillin as a novel and effective nitrification inhibitor
    (2023) Egenolf, Konrad; Schöne, Jochen; Conrad, Jürgen; Braunberger, Christina; Beifuß, Uwe; Arango, Jacobo; Rasche, Frank
    Introduction: Biological Nitrification Inhibition (BNI) is defined as the plant-mediated control of soil nitrification via the release of nitrification inhibitors. BNI of Brachiaria humidicola (syn. Urochloa humidicola) has been mainly attributed to root-exuded fusicoccane-type diterpenes, e.g., 3-epi-brachialactone. We hypothesized, however, that BNI of B. humidicola is caused by an assemblage of bioactive secondary metabolites. Methods: B. humidicola root exudates were collected hydroponically, and metabolites were isolated by semi-preparative HPLC. Chemical structures were elucidated by HRMS as well as 1D and 2D NMR spectroscopy. Nitrification inhibiting potential of isolated metabolites was evaluated by a Nitrosomonas europaea based bioassay. Results and discussion: Besides previously described brachialactone isomers and derivatives, five phenol and cinnamic acid derivatives were identified in the root exudates of B. humidicola: 2-hydroxy-3-(hydroxymethyl)benzaldehyde, vanillin, umbelliferone and both trans- and cis-2,6-dimethoxycinnamic acid. Notably, vanillin revealed a substantially higher nitrification inhibiting activity than 3-epi-brachialactone (ED50 ∼ 12.5 μg·ml−1, ED80 ∼ 20 μg·ml−1), identifying this phenolic aldehyde as novel nitrification inhibitor (NI). Furthermore, vanillin exudation rates were in the same range as 3-epi-brachialactone (1–4 μg·h−1·g−1 root DM), suggesting a substantial contribution to the overall inhibitory activity of B. humidicola root exudates. In relation to the verification of the encountered effects within soils and considering the exclusion of any detrimental impact on the soil microbiome, the biosynthetic pathway of vanillin via the precursor phenylalanine and the intermediates p-coumaric acid/ferulic acid (precursors of further phenolic NI) might constitute a promising BNI breeding target. This applies not only to Brachiaria spp., but also to crops in general, owing to the highly conserved nature of these metabolites.