Photochromic Metal–Organic Frameworks: Reversible Control of Singlet Oxygen Generation

The controlled generation of singlet oxygen is of great interest owing to its potential applications including industrial wastewater treatment, photochemistry, and photodynamic therapy. Two photochromic metal–organic frameworks, PC‐PCN and SO‐PCN, have been developed. A photochromic reaction has been successfully realized in PC‐PCN while maintaining its single crystallinity. In particular, as a solid‐state material which inherently integrates the photochromic switch and photosensitizer, SO‐PCN has demonstrated reversible control of ¹O₂ generation. Additionally, SO‐PCN shows catalytic activity towards photooxidation of 1,5‐dihydroxynaphthalene.     

Simultaneous chemical fingerprint and quantitative analysis of Rhizoma Smilacis Glabrae by accelerated solvent extraction and high‐performance liquid chromatography with tandem mass spectrometry

Rhizoma Smilacis Glabrae (RSG) is a well‐known herbal medicine with the homology of medicine and food. In this study, simultaneous chemical fingerprint and quantitative analysis of the bioactive flavonoid components of RSG were developed using accelerated solvent extraction and high‐performance liquid chromatography coupled with ion trap tandem mass spectrometry. The operational parameters of accelerated solvent extraction including extraction solvent, extraction temperature, static extraction time, solid‐to‐liquid ratio, and extraction cycles were optimized. Hierarchical cluster analysis, similarity analysis, and principal component analysis were performed to evaluate the similarity and variation of the samples collected from several provinces in China. Subsequently, high‐performance liquid chromatography fingerprints were established for the discrimination of 16 batches of RSG samples, and the major six flavonoids, namely, toxifolin, neoastilbin, astilbin, neoisoastilbin, isoastilbin, and engeletin were then quantitatively determined. The calibration curves for all the six analytes showed good linearity (r² > 0.999), and the limits of detection and quantification were less than 0.10 and 0.27 μg·mL^?1, respectively. Therefore, the proposed extraction and determination methods were proved to be robust and reliable for the quality control of RSG.     

Separation and purification of five alkaloids from Aconitum duclouxii by counter‐current chromatography

C₁₉‐diterpenoid alkaloids are the main components of Aconitum duclouxii Levl. The process of separation and purification of these compounds in previous studies was tedious and time consuming, requiring multiple chromatographic steps, thus resulted in low recovery and high cost. In the present work, five C₁₉‐diterpenoid alkaloids, namely, benzoylaconine ( 1 ), N‐deethylaconitine ( 2 ), aconitine ( 3 ), deoxyaconitine ( 4 ), and ducloudine A ( 5 ), were efficiently prepared from A. duclouxii Levl (Aconitum L.) by ethyl acetate extraction followed with counter‐current chromatography. In the process of separation, the critical conditions of counter‐current chromatography were optimized. The two‐phase solvent system composed of n‐hexane/ethyl acetate/methanol/water/NH₃·H₂O (25%) (1:1:1:1:0.1, v/v) was selected and 148.2 mg of 1 , 24.1 mg of 2 , 250.6 mg of 3 , 73.9 mg of 4, and 31.4 mg of 5 were obtained from 1 g total Aconitum alkaloids extract, respectively, in a single run within 4 h. Their purities were found to be 98.4, 97.2, 98.2, 96.8, and 96.6%, respectively, by ultra‐high performance liquid chromatography analysis. The presented separation and purification method was simple, fast, and efficient, and the obtained highly pure alkaloids are suitable for biochemical and toxicological investigation.     

Ultrasensitive non-enzymatic glucose sensing at near-neutral pH values via anodic stripping voltammetry using a glassy carbon electrode modified with Pt3Pd nanoparticles and reduced graphene oxide

We describe an anodic stripping voltammetric (ASV) method for glucose sensing that widely expands the typical amperometric i-t response of glucose sensors. The electrode is based on a working electrode consisting of a glassy carbon electrode modified with Pt-Pd nanoparticles (NPs; in an atomic ratio of 3:1) on a reduced graphene oxide (rGO) support. The material was prepared via the spontaneous redox reaction between rGO, PdCl₄ ²⁻ and PtCl₄ ²⁻ without any additional reductant or surfactant. Unlike known Pt-based sensors, the use of Pt₃Pd NPs results in an ultrasensitive ASV approach for sensing glucose even at near-neutral pH values. If operated at a working voltage as low as 0.06 V (vs. SCE), the modified electrode can detect glucose in the 2 nM to 300 μM concentration range. The lowest detectable concentration is 2 nM which is much lower than the LODs obtained with other amperometric i-t type sensing approaches, most of which have LODs at a μM level. The sensor is not interfered by the presence of 0.1 M of NaCl.

We describe an anodic stripping voltammetric method for glucose sensing that widely expands the typical amperometric i-t response of glucose sensors (2 nM to 300 μM). The electrode is based on a glassy carbon electrode modified with Pt-Pd nanoparticles on a reduced graphene oxide (rGO) support.

     

Two Uranyl Complexes with Pyromellitic Acid. A Heterometallic Complex with U=O–CuII Interaction

Two uranyl complexes based on pyromellitic acid were hydrothermally synthesized, and their X‐ray single‐crystal diffraction structures were determined. Complex [UO₂(Hbtec)]^–(Himd)⁺ · H₂O ( 1 ) (H₄btec = pyromellitic acid, imd = imidazole), is an ionic complex, which shows a typical (4, 4) topological structure in the space. A heterometallic complex, UO₂Cu(btec)(phen) ( 2 ) (phen = 1,10‐phenanthroline) results from the reaction of uranyl nitrate and copper(II) bromide with pyromellitic acid. The structure of complex 2 revealed that the chains of UO₇ and CuO₃N₂ units were connected to each other through the carboxyl groups and U=O–Cu interactions to create a two‐dimensional framework.     

Single nucleotide polymorphisms of mitochondrial DNA HVS‐I and HVS‐II in Chinese Bai ethnic group

For forensic and population genetic purposes, a total of 125 unrelated volunteers’ blood samples were collected from Chinese Bai ethnic minority group to analyze sequence variation of two hypervariable segments (HVS‐I and HVS‐II) in the mitochondrial DNA control region. Comparing the HVS‐I and HVS‐II sequences of the 125 Chinese Bais to the Anderson reference sequence, we found 86 polymorphic loci in HVS‐I and 40 in HVS‐II in mitochondrial DNA sequences of the Chinese Bai ethnic minority group, which defined 93 and 53 different haplotypes, respectively. Haplotype diversity and the mean pairwise differences were 0.992 ± 0.003 and 6.553 in HVS‐I, and 0.877 ± 0.027 and 2.407 in HVS‐II, respectively. We defined four macrohaplogroups R, M, N and D with the proportions ranging from 9.6% to 40.0%. With the analysis of the hypervariable domain from nucleotide 16 180–16 193 in HVS‐I, our study revealed new haplotypes of sequence variations. In addition, the Fst metric, phylogenetic tree, and principal component analysis demonstrated a close genetic relationship between the Bai group and Chinese Han populations from South China, Changsha, and Guangdong. The results support that the Bai group is a multiorigin ethnic minority that has merged with the Chinese Han population.     

Comprehensive characterization of natural organic matter by MALDI- and ESI-Fourier transform ion cyclotron resonance mass spectrometry

Natural organic matter (NOM) is a complex and non-uniform mixture of organic compounds which plays an important role in environmental processes. Due to the complexity, it is challenging to obtain fully detailed structural information about NOM. Although Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) has been demonstrated to be a powerful tool for providing molecular information about NOM, multiple ionization methods are needed for comprehensive characterization of NOM at the molecular level considering the ionizing selectivity of different ionization methods. This paper reports the first use of matrix assisted laser desorption/ionization (MALDI) method coupled with FT-ICR-MS for molecular characterization of NOM within a mass range of 200–800 Da. The mass spectral data obtained by MALDI were systematically compared with data generated by electrospray ionization (ESI). It showed that complementary molecular information about NOM which could not be detected by ESI, were provided by MALDI. More unsaturated and aromatic constituents of NOM with lower O/C ratio (O/C ratio < 0.5) were preferentially ionized in MALDI negative mode, whereas more polar constituents of NOM with higher O/C ratio were preferentially ionized in ESI negative mode. Molecular anions of NOM appearing at even m/z in MALDI negative ion mode were detected. The results show that NOM molecules with aromatic structures, moderate O/C ratio (0.7 > O/C ratio > 0.25) and lower H/C ratio were liable to form molecular anions at even m/z, whereas those with higher H/C ratio are more likely to form deprotonated ions at odd m/z. It is speculated that almost half of the NOM molecules identified by MALDI may be aromatic or condensed aromatic compounds with special groups which are liable to absorb electron from other molecules to generate free radical anions during MALDI ionization.     

The Cu-MOF-199/single-walled carbon nanotubes modified electrode for simultaneous determination of hydroquinone and catechol with extended linear ranges and lower detection limits

A novel electrochemical sensor based on Cu-MOF-199 [Cu-MOF-199 = Cu₃(BTC)₂ (BTC = 1,3,5-benzenetricarboxylicacid)] and SWCNTs (single-walled carbon nanotubes) was fabricated for the simultaneous determination of hydroquinone (HQ) and catechol (CT). The modification procedure was carried out through casting SWCNTs on the bare glassy carbon electrode (GCE) and followed by the electrodeposition of Cu-MOF-199 on the SWCNTs modified electrode. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were performed to characterize the electrochemical performance and surface characteristics of the as-prepared sensor. The composite electrode exhibited an excellent electrocatalytic activity with increased electrochemical signals towards the oxidation of HQ and CT, owing to the synergistic effect of SWCNTs and Cu-MOF-199. Under the optimized condition, the linear response range were from 0.1 to 1453 μmol L⁻¹ (R_HQ = 0.9999) for HQ and 0.1–1150 μmol L⁻¹ (R_CT = 0.9990) for CT. The detection limits for HQ and CT were as low as 0.08 and 0.1 μmol L⁻¹, respectively. Moreover, the modified electrode presented the good reproducibility and the excellent anti-interference performance. The analytical performance of the developed sensor for the simultaneous detection of HQ and CT had been evaluated in practical samples with satisfying results.     

New Monoterpenoids from Fruits of Gardenia jasminoides var. radicans

One new lactone, cyclopentanepyrone A ( 1 ), and two new monoterpenoids, gardeterpenone A ( 2 ) and jasminoside V ( 3 ), were isolated from the fruits of Gardenia jasminoides var. radicans, along with four known monoterpenoids, 4 – 7 , which were isolated from this plant for the first time. The structures of the isolates were elucidated by extensive spectroscopic studies, including UV, IR, 1D‐ and 2D‐NMR, ESI‐MS, HR‐ESI‐MS, and CD experiments.