Substituent Effects on EI-MS Fragmentation Patterns of 5-Allyloxy-1-aryl-tetrazoles and 4-Allyl-1-aryl-tetrazole-5-ones; Correlation with UV-Induced Fragmentation Channels

1,4- and 1,5-disubstituted tetrazoles possess enriched structures and versatile chemistry, representing a challenge for chemists. In the present work, we unravel the fragmentation patterns of a chemically diverse range of 5-allyloxy-1-aryl-tetrazoles and 4-allyl-1-aryl-tetrazolole-5-ones when subjected to electron impact mass spectrometry (EI-MS) and investigate the correlation with the UV-induced fragmentation channels of the matrix-isolated tetrazole derivatives. Our results indicate that the fragmentation pathways of the selected tetrazoles in EI-MS are highly influenced by the electronic effects induced by substitution. Multiple pathways can be envisaged to explain the mechanisms of fragmentation, frequently awarding common final species, namely arylisocyanate, arylazide, arylnitrene, isocyanic acid and hydrogen azide radical cations, as well as allyl/aryl cations. The identified fragments are consistent with those found in previous investigations concerning the photochemical stability of the same class of molecules. This parallelism showcases a similarity in the behaviour of tetrazoles under EI-MS and UV-irradiation in the inert environment of cryogenic matrices of noble gases, providing efficient tools for reactivity predictions, whether for analytical ends or more in-depth studies. Theoretical calculations provide complementary information to articulate predictions of resulting products.     

Anti-Inflammatory Activity and Mechanism of Isookanin,Isolated by Bioassay-Guided Fractionation from Bidens pilosa L.

Bidens pilosa L. (Asteraceae) has been used historically in traditional Asian medicine and is known to have a variety of biological effects. However, the specific active compounds responsible for the individual pharmacological effects of Bidens pilosa L. (B. pilosa) extract have not yet been made clear. This study aimed to investigate the anti-inflammatory phytochemicals obtained from B. pilosa. We isolated a flavonoids-type phytochemical, isookanin, from B. pilosa through bioassay-guided fractionation based on its capacity to inhibit inflammation. Some of isookanin’s biological properties have been reported; however, the anti-inflammatory mechanism of isookanin has not yet been studied. In the present study, we evaluated the anti-inflammatory activities of isookanin using lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. We have shown that isookanin reduces the production of proinflammatory mediators (nitric oxide, prostaglandin E₂) by inhibiting the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in LPS-stimulated macrophages. Isookanin also inhibited the expression of activator protein 1 (AP-1) and downregulated the LPS-induced phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-jun NH₂-terminal kinase (JNK) in the MAPK signaling pathway. Additionally, isookanin inhibited proinflammatory cytokines (tumor necrosis factor-a (TNF-α), interleukin-6 (IL-6), interleukin-8 (IL-8), and interleukin-1β (IL-1β)) in LPS-induced THP-1 cells. These results demonstrate that isookanin could be a potential therapeutic candidate for inflammatory disease.     

Influencing Factors on the Physicochemical Characteristics of Tea Polysaccharides

Tea polysaccharides (TPSs) are one of the main bioactive constituents of tea with various biological activities such as hypoglycemic effect, antioxidant, antitumor, and immunomodulatory. The bioactivities of TPSs are directly associated with their structures such as chemical composition, molecular weight, glycosidic linkages, and conformation among others. To study the relationship between the structures of TPSs and their bioactivities, it is essential to elucidate the structure of TPSs, particularly the fine structures. Due to the vast variation nature of monosaccharide units and their connections, the structure of TPSs is extremely complex, which is also affected by several major factors including tea species, processing technologies of tea and isolation methods of TPSs. As a result of the complexity, there are few studies on their fine structures and chain conformation. In the present review, we aim to provide a detailed summary of the multiple factors influencing the characteristics of TPS chemical structures such as variations of tea species, degree of fermentation, and preparation methods among others as well as their applications. The main aspects of understanding the structural difference of TPSs and influencing factors are to assist the study of the structure and bioactivity relationship and ultimately, to control the production of the targeted TPSs with the most desired biological activity.     

Activity Guided Isolation of Phenolic Compositions from Anneslea fragrans Wall. and Their Cytoprotective Effect against Hydrogen Peroxide Induced Oxidative Stress in HepG2 Cells

Anneslea fragrans Wall., commonly known as “Pangpo Tea”, is traditionally used as a folk medicine and healthy tea for the treatment of liver and intestine diseases. The aim of this study was to purify the antioxidative and cytoprotective polyphenols from A. fragrans leaves. After fractionation with polar and nonpolar organic solvents, the fractions of aqueous ethanol extract were evaluated for their total phenolic (TPC) and flavonoid contents (TFC) and antioxidant activities (DPPH, ABTS, and FRAP assays). The n-butanol fraction (BF) showed the highest TPC and TFC with the strongest antioxidant activity. The bio-guided chromatography of BF led to the purification of six flavonoids (1–6) and one benzoquinolethanoid (7). The structures of these compounds were determined by NMR and MS techniques. Compound 6 had the strongest antioxidant capacity, which was followed by 5 and 2. The protective effect of the isolated compounds on hydrogen peroxide (H₂O₂)-induced oxidative stress in HepG2 cells revealed that the compounds 5 and 6 exhibited better protective effects by inhibiting ROS productions, having no significant difference with vitamin C (p > 0.05), whereas 6 showed the best anti-apoptosis activity. The results suggest that A. fragrans could serve as a valuable antioxidant phytochemical source for developing functional food and health nutraceutical products.     

In Vitro Antiplasmodial and Cytotoxic Activities of Compounds from the Roots of Eriosema montanum Baker f. (Fabaceae)

Malaria remains one of the leading causes of death in sub-Saharan Africa, ranked in the top three infectious diseases in the world. Plants of the Eriosema genus have been reported to be used for the treatment of this disease, but scientific evidence is still missing for some of them. In the present study, the in vitro antiplasmodial activity of the crude extract and compounds from Eriosema montanum Baker f. roots were tested against the 3D7 strain of Plasmodium falciparum and revealed using the SYBR Green, a DNA intercalating compound. The cytotoxicity effect of the compounds on a human cancer cell line (THP-1) was assessed to determine their selectivity index. It was found that the crude extract of the plant displayed a significant antiplasmodial activity with an IC₅₀ (µg/mL) = 17.68 ± 4.030 and a cytotoxic activity with a CC₅₀ (µg/mL) = 101.5 ± 12.6, corresponding to a selective antiplasmodial activity of 5.7. Bioactivity-guided isolation of the major compounds of the roots’ crude extract afforded seven compounds, including genistein, genistin and eucomic acid. Under our experimental conditions, using Artemisinin as a positive control, eucomic acid showed the best inhibitory activity against the P. falciparum 3D7, a well-known chloroquine-sensitive strain. The present results provide a referential basis to support the traditional use of Eriosema species in the treatment of malaria.     

Photoinduced rotational isomerization mechanism of 2-chlorobenzaldehyde in low-temperature rare-gas matrices by vibrational and electronic spectroscopies

Rotational isomerization of 2-chlorobenzaldehyde in low-temperature rare-gas matrices has been investigated by vibrational and electronic spectroscopies with aids of the density functional theory (DFT) and configuration interaction single (CIS) calculations. Infrared spectrum of the less stable O-cis isomer, produced from the more stable O-trans isomer upon UV irradiation, is measured with an FT-IR spectrophotometer. The enthalpy difference between the O-cis and O-trans isomers is estimated to be 9.7±0.2 kJ mol⁻¹ from the temperature dependence of the infrared band intensities. Analyses of the infrared and electronic absorption spectral changes after UV irradiation and the phosphorescence spectra measured at various excitation wavelengths suggest that the rotational isomerization occurs via the intersystem crossing from S₁ to T₁.     

桑黄黄酮A和B的分离与合成

利用正相硅胶柱色谱，Sephadex LH-20柱色谱以及反相HPLC等手段从真菌桑黄 中分离得到两个新的二氢黄酮衍生物，经1D NMR，2D NMR和MS等光谱方法鉴定其结 构分别为5，7，4'－三羟基－6－邻羟苄基二氢黄酮和5，7，4'-三羟基－8－邻羟 苄基二氢黄酮，并且对它们进行了合成。     

Low-pressure pyrolysis of tBu2SO: synthesis and IR spectroscopic detection of HSOH

Sulfenic acid (HSOH, 1 ) has been synthesized in the gas‐phase by low‐pressure high‐temperature (1150 °C) pyrolysis of di‐tert‐butyl sulfoxide (tBu₂SO, 2 ) and characterized by means of matrix isolation and gas‐phase IR spectroscopy. High‐level coupled‐cluster (CC) calculations (CCSD(T)/cc‐pVTZ and CCSD(T)/cc‐pVQZ) support the first identification of the gas‐phase IR spectrum of 1 and enable its spectral characterization. Five of the six vibrational fundamentals of matrix‐isolated 1 have been assigned, and its rotational‐resolved gas‐phase IR spectrum provides additional information on the O–H and S–H stretching fundamentals. Investigations of the pyrolysis reaction by mass spectrometry, matrix isolation, and gas‐phase FT‐IR spectroscopy reveal that, up to 500 °C, 2 decomposes selectively into tert‐butylsulfenic acid, (tBuSOH, 3 ), and 2‐methylpropene. The formation of the isomeric sulfoxide (tBu(H)SO, 3 a ) has been excluded. Transient 3 has been characterized by a comprehensive matrix and gas‐phase vibrational IR study guided by the predicted vibrational spectrum calculated at the density functional theory (DFT) level (B3LYP/6‐311+G(2d,p)). At higher temperatures, the intramolecular decomposition of 3 , monitored by matrix IR spectroscopy, yields short‐lived 1 along with 2‐methylpropene, but also H₂O, and most probably sulfur atoms. In addition, HSSOH ( 6 ), H₂, and S₂O are found among the final pyrolysis products observed at 1150 °C in the gas phase owing to competing intra‐ and intermolecular decomposition routes of 3 . The decomposition routes of the starting compound 2 and of the primary intermediate 3 are discussed on the basis of experimental results and a computational study performed at the B3LYP/6‐311G* and second‐order Møller–Plesset (MP2/6‐311G* and RI‐MP2/QZVPP) levels of theory.     

Thioacetylacetone: structural and vibrational assignments.

Thioacetylacetone and its variously deuterated isotopomers have been investigated using electronic and vibrational spectroscopy combined with quantum chemical calculations. Thioacetylacetone is known for its photochromic properties, but the structures of the initial and final forms have been the subject of a long debate. Analysis of the IR spectra recorded in low-temperature argon and xenon matrices, room-temperature solutions, and in the gas phase has allowed us to establish the nature of the photochromic species and of its precursor. Similar to the case of another beta-thioxoketone, monothiodibenzoylmethane, the photo-product has been assigned to the nonchelated SH exo-rotamer of the (Z)-enethiol tautomeric form, whereas the dominant ground-state species corresponds to the chelated (Z)-enol tautomeric form. Detailed vibrational assignments have been proposed for both forms based on quantum chemical calculations and polarization experiments. In the case of the chelated (Z)-enol species prevailing in the ground state, a second-order perturbative anharmonic analysis at the B3LYP/cc-pVTZ level indicated strong anharmonic effects associated with the intramolecular hydrogen bond, leading to a shift of more than 600 cm-1 of the wavenumber of the OH-stretching vibration. A small fraction of the SH endo-rotameric chelated (Z)-enethiol form was also detected under unperturbed conditions. The (Z)-enethiol form can be converted into the (Z)-enol form by irradiation at 290 nm.     

Bromsuperoxid: Bildung und Photoisomerisierung zu Bromdioxid

Bromine Superoxide: Generation and Photoisomerization into Bromine Dioxide Flash pyrolysis of a gas mixture containing bromine, oxygen and argon yields bromine superoxide, which can be identified IR- and UV-spectroscopically after trapping the pyrolysate at 12 K. Matrix irradiation transfers bromine superoxide into bromine dioxide. The backreaction can be induced by changing the wavelength. Even at room temperature a detectable amount of bromine superoxide is formed upon preparing a mixture of gaseous bromine, oxygen and argon.