Computational and Spectroscopic Studies on the Formation of Halogen-Bonded Complexes Between Tertiary Amines and CBr4 and Application in the Light-Mediated Amino Acid Coupling.

In recent years, halogen-bonded complexes (XBCs), in solution, have played a pivotal role in inducing photochemical organic reactions. In this work, we explore the ability of various tertiary amines to act as XB acceptors in the presence of the XB donor CBr4 by computational and spectroscopic studies. DFT studies clearly showcase the formation of XBCs between the studied tertiary amines and CBr4. Simultaneously, computational and experimental UV-Vis studies display intense red shifts that are consistent with charge transfer observed from tertiary amines to CBr4. A detailed NMR study revealed a clear chemical shift of the carbon carrying the bromine atoms upon mixing the XB acceptor with the donor, suggesting that this spectroscopic technique is indeed an experimental tool to identify the generation of XBCs. An application of the ability of such XBCs to activate a carboxylic acid under UVA irradiation or sunlight is presented for amino acid coupling. Among the various tertiary amines studied, the pair DABCO-CBr4 was found to work well for the photochemical amide bond formation. Direct infusion-HRMS studies allowed us to propose a general mechanism for the photochemical amino acid coupling in the presence of a tertiary amine and CBr4, initiated by the photoactivation of an XBC.

Edible flowers from Theobroma speciosum: Aqueous extract rich in antioxidant compounds.

Theobroma speciosum, known as "cacauí" in Brazil, is considered a prominent unconventional food plant. The objective of this work was to evaluate the chemical profiles, antioxidant capacity and minerals of the aqueous extract and fractions from its flowers. The identified compounds were sugars, organic acids and phenolics compounds such as citric, malic and protocatechuic acids, quercetin, quercetin pentoside and quercetin-3-O-glucoside. The extract was rich in phenolic compounds (640 mg GAE g-1). Furthermore, fractions also presented phenolic compounds from 170.7 to 560.7 mg GAE g-1 (mainly protocatechuic acid, quercetin and derivatives), which influenced on the high antioxidant capacity in DPPH, ABTS, FRAP and co-oxidation ß-carotene/linolenic acid assays. Flowers presented potassium (115 ± 2 µg mL-1), magnesium (18.4 ± 0.2 µg mL-1), phosphorus (7.0 ± 0.0 µg mL-1) and calcium (3.1 ± 0.1 µg mL-1). Moreover, the flowers aqueous extract represents a new promising food source rich in antioxidant compounds.

Metabolic fingerprinting reveals extensive consequences of GLS hyperactivity.

BACKGROUND: High glutaminase (GLS;EC3.5.1.2) activity is an important pathophysiological phenomenon in tumorigenesis and metabolic disease. Insight into the metabolic consequences of high GLS activity contributes to the understanding of the pathophysiology of both oncogenic pathways and inborn errors of glutamate metabolism. Glutaminase catalyzes the conversion of glutamine into glutamate, thereby interconnecting many metabolic pathways. METHODS: We developed a HEK293-based cell-model that enables tuning of GLS activity by combining the expression of a hypermorphic GLS variant with incremental GLS inhibition. The metabolic consequences of increasing GLS activity were studied by metabolic profiling using Direct-Infusion High-Resolution Mass-Spectrometry (DI-HRMS). RESULTS AND CONCLUSIONS: Of 12,437 detected features [m/z], 109 features corresponding to endogenously relevant metabolites were significantly affected by high GLS activity. As expected, these included strongly decreased glutamine and increased glutamate levels. Additionally, increased levels of tricarboxylic acid (TCA) intermediates with a truncation of the TCA cycle at the level of citrate were detected as well as increased metabolites of transamination reactions, proline and ornithine synthesis and GABA metabolism. Levels of asparagine and nucleotide metabolites showed the same dependence on GLS activity as glutamine. Of the nucleotides, especially metabolites of the pyrimidine thymine metabolism were negatively impacted by high GLS activity, which is remarkable since their synthesis depend both on aspartate (product of glutamate) and glutamine levels. Metabolites of the glutathione synthesizing γ-glutamyl-cycle were either decreased or unaffected. GENERAL SIGNIFICANCE: By providing a metabolic fingerprint of increasing GLS activity, this study shows the large impact of high glutaminase activity on the cellular metabolome.