Undescribed Phenolic Glycosides from Syzygium attopeuense and Their Inhibition of Nitric Oxide Production

Posted on 23 September 2023 by

Abstract

Four undescribed phenolic glycosides including three stilbene derivatives (1 and 3) and sodium salt of 3 (2), and a chalcone glycoside (4), together with thirteen known compounds (5–17) were isolated from the leaves of Syzygium attopeuense (Gagnep.) Merr. & L.M.Perry. Their chemical structures were elucidated to be (Z)-gaylussacin (1), 6′′-O-galloylgaylussacin sodium salt (2), 6′′-O-galloylgaylussacin (3), 4′-O-[β-D-glucopyranosyl-(1→6)-glucopyranosyl]oxy-2′-hydroxy-6′-methoxydihydrochalcone (4), gaylussacin (5), pinosilvin 3-O-β-D-glucopyranoside (6), myricetin-3-O-(2′′-O-galloyl)-α-L-rhamnopyranoside (7), myricetin-3-O-(3′′-O-galloyl)-α-L-rhamnopyranoside (8), myricetin-3-O-α-L-rhamnopyranoside (9), quercitrin (10), myricetin-3-O-β-D-glucopyranoside (11), myricetin-3-O-β-D-galactopyranoside (12), quercetin 3-O-α-L-arabinopyranoside (13), myricetin-3-O-2′′-O-galloyl)-α-L-arabinopyranoside (14), (+)-gallocatechin (15), (−)-epigallocatechin (16), and 3,3’,4’-trimethoxyellagic acid 4-O-β-D-glucopyranoside (17) by the analysis of HR-ESI-MS, 1D and 2D NMR spectra in comparison with the previously reported data. Compounds 1–3, 5, and 6 significant inhibition of NO production in LPS-activated RAW264.7 cells, with IC₅₀ values ranging from 18.37±1.38 to 35.12±2.53 μM, compared to a positive control (dexamethasone) with an IC₅₀ value of 15.37±1.42 μM.

Casearia Essential Oil: An Updated Review on the Chemistry and Pharmacological Activities

Posted on 23 September 2023 by

Abstract

Casearia species are found in the America, Africa, Asia, and Australia and present pharmacological activities, besides their traditional uses. Here, we reviewed the chemical composition, content, pharmacological activities, and toxicity of the essential oils (EOs) from Casearia species. The EO physical parameters and leaf botanical characteristics were also described. The bioactivities of the EOs from the leaves and their components include cytotoxicity, anti-inflammatory, antiulcer, antimicrobial, antidiabetic, antioxidant, antifungal, and antiviral activities. The main components associated with these activities are the α-zingiberene, (E)-caryophyllene, germacrene D, bicyclogermacrene, spathulenol, α-humulene, β-acoradiene, and δ-cadinene. Data on the toxicity of these EOs are scarce in the literature. Casearia sylvestris Sw. is the most studied species, presenting more significant pharmacological potential. The chemical variability of EOs components was also investigated for this species. Caseria EOs have relevant pharmacological potential and must be further investigated and exploited.

Front Cover: Chemistry and Bioactivity of the Genus Persea ‐ A Review (Chem. Biodiversity 9/2023)

Posted on 23 September 2023 by

Front Cover. This review comprehensively assesses bioactive compounds in Persea species (1950-2023). Different metabolites, such as flavonoids (32), terpenoids (31), fatty alcohols (30), lignoids (19), and γ-lactone derivatives (18) were identified. These compounds displayed diverse properties such as insecticidal, antibacterial, antifungal, antiviral, cytotoxic, anti-inflammatory, and antioxidant. This review enriches the knowledge of bioactive compounds in the genus Persea as reported by main authors et al. in their article at 10.1002/cbdv.202300947.

Synthetic Approaches to Ribosyl Adenosine 5′,5″‐Diphosphate Fragment of Poly(ADP‐ribose)

Posted on 23 September 2023 by

Ribosyl adenosine 5′,5″-diphosphate is a poly(ADP-ribose) fragment covalently bonded to a protein during post-translational modification. Poly(ADP-ribose) is involved in several biological processes such as DNA repair and cancerization. Herein, we report the development of two synthetic approaches to the poly(ADP-ribose) fragment via a common precursor. The major difficulty in the synthesis of the fragment is the α-(1″→2′)-glycosidic bond formation between the ribose and adenosine because of the lack of neighboring group participation and low reactivity of the 2′-hydroxyl group. The first approach employed an indirect method that involved stepwise assembly of the ribosyl adenosine framework by O-ribofuranosylation of a commercially available ribose acceptor and subsequent N-glycosylation of N6-benzoyl adenine (11 linear longest sequence (LLS) steps, 14.5% overall yield). In the second approach, the direct O-ribofuranosylation of a known 6-chloropurine riboside acceptor was adopted (9 LLS steps, 10.3% overall yield). Thus, two practical synthetic approaches to the target fragment were successfully established in terms of the number of LLS steps and overall yield. Furthermore, the precursor was converted into a conjugation-ready building block, primed for application in ADP-ribose oligomer synthesis.

Recent Advances in Bimetallic Catalysts for Methane Steam Reforming in Hydrogen Production: Current Trends, Challenges, and Future Prospects

Posted on 23 September 2023 by

The primary method for hydrogen production is through methane steam reforming (MSR) of natural gas. This process involves the reaction between methane and steam to create a synthesis gas (syn gas). Following this, a step referred to as water-gas shift (WGS) is employed. During the WGS process, the hydrogen content is enhanced as H₂O reacts with CO at lower temperatures. Subsequently, hydrogen is extracted from the gas using pressure swing adsorption (PSA). The remaining off-gas is combusted with additional natural gas to generate the heat necessary for MSR. It is imperative to emphasize the significance of synthesizing steam reforming catalysts with high activity and durability to enable large-scale hydrogen production. Recent advancements in bimetallic catalysts for steam reforming have led to enhanced performance in steam methane reforming. This improvement is attributed to the synergistic interaction between two metals in the catalyst.

Abstract

As energy demand continues to rise and the global population steadily grows, there is a growing interest in exploring alternative, clean, and renewable energy sources. The search for alternatives, such as green hydrogen, as both a fuel and an industrial feedstock, is intensifying. Methane steam reforming (MSR) has long been considered a primary method for hydrogen production, despite its numerous advantages, the activity and stability of the conventional Ni catalysts are major concerns due to carbon formation and metal sintering at high temperatures, posing significant drawbacks to the process. In recent years, significant attention has been given to bimetallic catalysts as a potential solution to overcome the challenges associated with methane steam reforming. Thus, this review focuses on the recent advancements in bimetallic catalysts for hydrogen production through methane steam reforming. The review explores various aspects including reactor type, catalyst selection, and the impact of different operating parameters such as reaction temperature, pressure, feed composition, reactor configuration, and feed and sweep gas flow rates. The analysis and discussion revolve around key performance indicators such as methane conversion, hydrogen recovery, and hydrogen yield.

Glu‐derived zwitterionic micelles with conquering the intestinal mucosal barrier toward oral delivery

Posted on 23 September 2023 by nKedong Liu, nYun Chen, nDutao Yang, nYanfei Cai, nZhaoqi Yang, nJian Jinn

Amino acid transporters with different categories are highly expressed in intestinal epithelial cells for maintaining the essential metabolism of body. The zwitterioninc property of amino acid with α-amino and α-carboxyl also has tremendous potential to conquer the mucus barrier. Therefore, two glutamic acid (Glu)-derived amphiphilic block polymers [poly(lactic acid)-b-poly(glutamine)25 (PPQ) and poly(lactic acid)-b-poly(glutamate)25 (PPD)] were rational designed and further prepared Glu-derived zwitterionic micelles (PPQ-M and PPD-M) toward oral delivery. In comparison with PEG-M (PEG micelles), two Glu-derived zwitterionic micelles revealed superior mucus permeability. In addition, enhanced cellular internalization was also confirmed in both zwitterionic micelles, which were mainly mediated by multiple amino acid transporters. It was speculated that the uptake efficiency of PPQ-M was obviously higher than that of PPD-M due to PPQ-M with higher affinity of glutamine structural unit. Furthermore, the retrograde pathway played an important role in the intracellular transport of both zwitterionic micelles as well as transcytosis transport. Excellent villi absorption in situ of Glu-derived zwitterionic micelles were observed, which gave a convincing evidence for oral delivery potential. The results of this research demonstrated that Glu-derived zwitterionic micelles with unquestionable capacity of conquering intestinal mucosal barrier, have promising application toward oral delivery.

Accuracy of expectation values of one‐electron operators obtained from Hartree–Fock wavefunctions expanded using Lambda functions

Posted on 23 September 2023 by nYasuyo Hatano, nShigeyoshi Yamamoto, nHiroshi Tatewakin

The number of significant figures (SF) of the cusp condition (CC) is approximately half that of the Hartree–Fock total energy (TE). The SFs of expectation values of the other one-electron properties are also smaller than for the TE.

Abstract

The accuracy of the expectation values (<A>$$ <A> $$) of one-electron operators is examined using Hartree–Fock wavefunctions expanded using Λ$$ \Lambda $$ functions. In this expansion, 150 terms, then 149, 148, and 147 terms are used for the s-, p-, d-, and f-symmetries, respectively. The systems investigated are He–Ne and the Group 18 atoms of Ar–Og. The one-electron properties investigated are the cusp condition (CC), the electron density at the nucleus (ρ(0)$$ \rho (0) $$), and <ri>$$ <{r}^i> $$ (i=−2,…,9$$ i=-2,\dots, 9 $$). Convergence of <A>$$ <A> $$ is examined by increasing the number of expansion terms (N$$ N $$) up to the given limit (150). The number of significant figures (SF) of <A>$$ <A> $$ is counted by comparing the calculated value at N$$ N $$=150 (<A(150)>$$ <A(150)> $$) with the extrapolated value <A(∞)>$$ <A\left(\infty \right)> $$. For He, the SF of CC is found to be 26. For the atoms under consideration, the SF of CC is approximately half that of the total energy (TE). The SFs of expectation values of the other properties are also smaller than for the TE.

XMe ‐ Xiamen Molecular Electronics code: an intelligent and open‐source data analysis tool for single‐molecule conductance measurements

Posted on 22 September 2023 by

Comprehensive Summary

Charge transport characterization of single-molecule junctions is essential for the fundamental research of single-molecule physical chemistry and the development towards single-molecule electronic devices and circuits. Among the single-molecule conductance characterization techniques, the single-molecule break junction technique is widely used in tens of worldwide research laboratories which can generate a large amount of experimental data from thousands of individual measurement cycles. However, data interpretation is a challenging task for researchers with different research backgrounds, and the different data analysis approaches sometimes lead to the misunderstanding of the measurement data and even reproducibility issues of the measurement. It is thus a necessity to develop a user-friendly all-in-one data analysis tool that automatizes the basic data analysis in a standard and widely accepted way. In this work, we present the XMe Code (Xiamen Molecular Electronics Code), an intelligent all-in-one data analysis tool for the comprehensive analysis of single-molecule break junction data. XMe code provides end-to-end data analysis that takes in the original experimental data and returns electronic characteristics and even charge transport mechanisms. We believe that XMe Code will promote the transparency of the data analysis in single-molecule electronics and the collaborations among scientists with different research backgrounds.

Efficient Synthesis and Microwave‐Assisted Sonogashira Reactions of Triflate‐Substituted Porphyrin

Posted on 22 September 2023 by

Porphyrins that bear halogens at the meso-aryl positions are useful building blocks for the preparation of light-harvesting arrays and materials through cross-coupling procedures. Despite the wide use of such intermediates, their scale-up and purification are usually hampered by tedious chromatographic separations because of the statistical nature of the synthetic protocol and the similar polarity of the different products. Here, we propose the use of porphyrins bearing a triflatophenyl group as alternative starting materials for palladium cross-coupling reactions. In particular, purification of the zinc 5,10,15-triaryl-20-(4-triflatophenyl)porphyrin (ZnP-OTf) model compound by column chromatography proved to be much easier compared to porphyrin analogues that carry halogen substituents. This is the result of the increased polarity of compounds functionalized by highly polar triflate groups if compared to those substituted by halogens. To show the value of the triflatophenylporphyrin model compound in cross-coupling reactions, we developed a microwave-assisted Sonogashira protocol that quantitatively converts the ZnP-OTf to the corresponding alkynylphenylporphyrin, in relatively short reaction times. Finally, we showed that the proposed ZnP-OTf building block can be conveniently converted into an alkynyl-linked molecular wire to bridge the zinc porphyrin donor with the [60]fullerene acceptor in a molecular dyad.

Application of an Oscillatory Plug Flow Reactor to Enable Scalable and Fast Reactions in Water Using a Biomass‐Based Polymeric Additive

Posted on 22 September 2023 by

The utilization of water as a sustainable reaction medium has important advantages over traditional organic solvents. Hydroxypropyl methylcellulose has emerged as a biomass-based polymeric additive that enables organic reactions in water through hydrophobic effects. However, such conditions imply slurries as reaction mixtures, where the efficacy of mass transfer and mixing decreases with increasing vessel size. In order to circumvent this limitation and establish an effectively scalable platform for performing hydroxypropyl methylcellulose-mediated aqueous transformations, we utilized oscillatory plug flow reactors that feature a smart dimensioning design principle across different scales. Using nucleophilic aromatic substitutions as valuable model reactions, rapid parameter optimization was performed first in a small-scale instrument having an internal channel volume of 5 mL. The optimal conditions were then directly transferred to a 15 mL reactor, achieving a three-fold scale-up without re-optimizing any reaction parameters. By precisely fine-tuning the oscillation parameters, the system achieved optimal homogeneous suspension of solids, preventing settling of particles and clogging of process channels. Ultimately, this resulted in a robust and scalable platform for performing multiphasic reactions under aqueous conditions.