Magnetic Resonance in Chemistry

Wu, Qiong; Li, Yan; Yuan, Bin; Xu, Qing; Liu, Yanfang

doi: 10.1002/mrc.70123pmid: 42289892

Isodon rubescens is a widely used traditional folk medicine in China. In this study, 13 natural products were isolated using a two‐step ethanol extraction. Notably, flavonoid glycosides 2 and 4, and polymeric caffeic acids 7 and 8, were identified for the first time from the secondary extraction residues, highlighting the continued presence of bioactive compounds with potential for further development. Oridonin (9), the major active compound, was quantified in nine commercial preparations using quantitative NMR (qNMR). Its concentration in the drop pill (0.92 mg/g) was comparable to that in the raw extract (0.90 mg/g). The three tablet samples showed varying levels: Tablet 3 (2.66 mg/g) > Tablet 1 (1.22 mg/g) > Tablet 2 (1.09 mg/g). Capsule, tea bag, and syrup samples could not be quantified due to low concentrations.

Zhu, Yun‐chao; Ding, Chang‐chun; Sun, De‐chuan; Fan, Zhi‐xiang

doi: 10.1002/mrc.70122pmid: 42235988

To clarify the correlation between the V4+ doping and the structure of DUT‐5(Al), this study establishes a theoretical calculation model for the electron paramagnetic resonance (EPR) parameters of V4+ with a 3d1 electron configuration in orthorhombically compressed octahedrons. After verifying the rationality of the model by fitting with experimental data, the local structural distortion of [VO6] clusters, the regulation mechanism of electronic states, and the essence of EPR components (lp, np, BL, and Blp) were systematically analyzed. The findings reveal that, due to the Jahn–Teller distortion, the [VO6] units adopt an orthorhombically distorted octahedral structure, quantified by an axial compression parameter ρ ranging from 5.6% to 6.4%, and in‐plane bond‐length variation rate τ spanning 6.0% to 6.8%. The theoretical method adopted in this study can clarify the doping mechanism of transition metal ions in metal–organic frameworks (MOFs), provide theoretical support for interpreting the EPR phenomena of V4+‐doped DUT‐5(Al), and offer guidance for the rational design and performance optimization of transition metal‐doped MOF materials.

Reyes‐Colón, Kiara T.; Díaz Corretjer, Carla M.; Sang‐Laboy, Branlee; Vlaar, Cornelis P.; Bayro, Marvin J.

doi: 10.1002/mrc.70121pmid: 42287084

Characterizing protein–drug interactions at the atomic level is challenging partly because small molecules can be difficult to detect within large biomolecular complexes. We have developed a strategy to introduce NMR‐active isotopic 15N labels into derivatives of bevirimat (BVM), a triterpenoid inhibitor of HIV‐1 maturation. Isotopically labeled compounds were synthesized through concise and efficient routes using commercially available, isotopically enriched building blocks. Three 15N‐labeled BVM derivatives were prepared to be used as molecular probes to investigate HIV‐1 protein interactions. These labeled compounds enable site‐specific 15N detection of the inhibitor in both solution and solid‐state NMR experiments, which will be useful to obtain molecular‐level insight into the interactions between BVM derivatives and its target HIV‐1 Gag protein. Synthetic incorporation of NMR‐active isotopes produces chemical probes for atomic‐level analysis of next‐generation HIV‐1 therapeutics derived from BVM and can be applied to other derivatives of betulinic acid with various medical applications.