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The present study used untargeted metabolomics to investigate the short-term metabolic changes induced in wheat seedlings by the specialized metabolite umbelliferone, an allelochemical. We used 10 day-old wheat seedlings treated with 104 μM umbelliferone over a time course experiment covering 6 time points (0 h, 6 h, 12 h, 24 h, 48 h, and 96 h), and compared the metabolomic changes to control (mock-treated) plants. Using gas chromatography mass spectrometry (GCMS)-based metabolomics, we obtained quantitative data on 177 metabolites that were derivatized (either derivatized singly or multiple times) or not, representing 139 non-redundant (unique) metabolites. Of these 139 metabolites, 118 were associated with a unique Human Metabolome Database (HMDB) identifier, while 113 were associated with a Kyoto Encyclopedia of Genes and Genomes (KEGG) identifier. Relative quantification of these metabolites across the time-course of umbelliferone treatment revealed 22 compounds (sugars, fatty acids, secondary metabolites, organic acids, and amino acids) that changed significantly (repeated measures ANOVA, P-value < 0.05) over time. Using multivariate partial least squares discriminant analysis (PLS-DA), we showed the grouping of samples based on time-course across the control and umbelliferone-treated plants, whereas the metabolite-metabolite Pearson correlations revealed tightly formed clusters of umbelliferone-derived metabolites, fatty acids, amino acids, and carbohydrates. Also, the time-course umbelliferone treatment revealed that phospho-l-serine, maltose, and dehydroquinic acid were the top three metabolites showing highest importance in discrimination among the time-points. Overall, the biochemical changes converge towards a mechanistic explanation of the plant metabolic responses induced by umbelliferone. In particular, the perturbation of metabolites involved in tryptophan metabolism, as well as the imbalance of the shikimate pathways, which are strictly interconnected, were significantly altered by the treatment, suggesting a possible mechanism of action of this natural compound.

The research on heterometallic 3d-4f polyoxometalates has made immense progress over the last decade with a larger number of structures being reported every year until the present day. The formation of 3d-4f POMs has been considered a challenge as both the 3d and 4f ions compete for coordination to the lacunary POMs ligands. It was seen that mostly amorphous precipitate was obtained instead of crystalline material. Hence, as a result, the synthetic parameters such as pH, temperature, solvent, time of reaction has to be precisely controlled in order to isolate the desired product. This review focuses on the heterometallic 3d-4f polyoxometalates reported in the last decade mainly after 2011, when the field of 3d-4f heterometallic polyoxometalates was considered an incipient field. The structural variety exhibited by this kind is diverse with a large number of structures including dimers, trimers, tetramers which can be divided mainly into four types of polyanions. These are pure 3d-4f polyanions, 3d substituted anions with 4f linkers, 4f substituted anions with 3d linkers, and POMs with both 3d and 4f as linkers. The reason for the desire to create such complexes is mainly due to the interesting magnetic properties exhibited by them. Introduction of 4f ions into the paramagnetic 3d cluster enhances the already present magnetic properties and allows the formation of single-molecule/ion magnets (SMMs or SIMs). Many of the complexes show slow magnetic relaxation which is ideal for SMMs/SIMs. A few of the complexes displaying such properties are discussed in the review. Apart from that, the catalytic properties exhibited by such 3d-4f complexes have also been discussed.