A new 1,2-diketone physalin isolated from Physalis minima and TRAIL-resistance overcoming activity of physalins

Chemical Constituents and α-Glucosidase Inhibitory Activities of the Leaves of Embelia parviflora-In Vitro and In Silico Studies

Phytochemical investigation of the methanol extract of Embelia parviflora Wall. Ex A. DC. leaves (Primulaceae family) led to the isolation of sixteen compounds including three sterols (1-3), one triterpene (4), four flavonoids (5-8), four megastigmanes (9-12), three phenolic compounds (13-15), and one furan derivative (16). Their chemical structures were determined based on ESI-MS and NMR spectral data. This is the first chemical study of E. parviflora. Compounds 3, 8-13, and 16 were found in the Embelia genus for the first time. Compounds 9-11, 13, and 16 represent the first isolation from the Primulaceae family. In the α-glucosidase activity assay, MeOH extract, compounds 4 and 5 strongly inhibited enzyme α-glucosidase activity. A molecular docking study revealed that compounds 4 and 5 showed different interactions with enzyme α-glucosidase.

Photocatalytic C-C bond thio(seleno)esterification of 1,2-diketone-derived pro-aromatic intermediates

We report an organophotocatalyst-enabled oxidant-free C-S/C-Se bond coupling of (un)symmetrical 1,2-diketones via pro-aromatic dihydroquinazolinones/benzothiazolines, employing readily accessible disulfides/diselenides. In this scalable and redox-neutral method, various dialkyl, di(hetero)aryl, and alkyl-aryl 1,2-diketones are expediently converted to S-aryl (S-alkyl) alkyl/(hetero)aryl thioesters and Se-alkyl aryl selenoesters with broad functional group compatibility in high efficiency.

Antitrypanosomal activity of Crossopteryx febrifuga and phytochemical profiling using LC-MS/MS analysis coupled to molecular network and SIRIUS

Crossopteryx febrifuga (Rubiaceae) is a plant widely used in traditional African medicine to treat tryapnosomiasis. The aim of our study was to evaluate the antitrypanosomal activity of C. febrifuga extracts and to identify the compounds responsible for this activity. We prepared 4 extracts by successive maceration of plant leaf powder in n-hexane, dichloromethane, methanol and water. The antitrypanosomal activity of the extracts was assessed on Trypanosoma brucei brucei and their selectivity on Leishmania mexicana mexicana and human non cancer WI38 fibroblast cells. The dichloromethane extract, the most antitrypanosomal (IC50 of 9.3 ± 0.8 μg/mL) was fractionated on an Open Column Chromatography to give 14 fractions. Fractions 6-9 were the most active with an IC50 ranging from 1.3 to 2.1 μg/mL. All fractions were analyzed by UPLC-ZenoTOFHRMS, followed by manual dereplication of metabolites detected in the most active fractions. Manual dereplication was aided by the Molecular Network (MN) and SIRIUS. Metabolic profiling of fractions 6-9 has enabled us to identify 33 compounds, most of which were reported for the first time in C. febrifuga. These include buddlenol C (6), naringenin (7), maslinic acid (22), corosolic acid or isomer (24), asperphenamate (25), hydroxyoctadecenoic acid (29), sumaresinolic acid or isomer I and II (30 and 31), glycyrrhetinic acid (32) and oleanolic acid (36). The bioactivity-based approach identified maslinic (22), corosolic (24), and oleanolic (36) acids as linked to the antitrypanosomal activity. The data obtained support the traditional use of C. febrifuga in the traditional treatment of trypanosomiasis. Further studies are required to verify the activity observed in vivo.

Mimicking Ozonolysis via Mechanochemistry: Internal Alkynes to 1,2-Diketones using H5IO6

Utilizing periodic acid as an environmentally benign oxidizing agent, this study introduces a novel mechanochemical method that mimics ozonolysis to convert internal alkynes into 1,2-diketones, showcasing effective emulation of ozone's reactivity. Notably, this oxidation occurs at room temperature in aerobic conditions, eliminating the need for toxic transition metals, hazardous oxidants, or expensive solvents. Through control experiments validating the mechanism, substantial evidence supports a concerted reaction pathway. This progress marks a significant stride toward cleaner and more efficient chemical synthesis, mitigating the environmental impact of conventional processes. Assessing the green chemistry metrics in both solvent-free and previously reported solvent-based methods, our eco-friendly protocol demonstrates an E-factor of 7.40, a 51.7 % atom economy, a 45.5 % atom efficiency, 100 % carbon efficiency, and 11.9 % reaction mass efficiency when solvents are not used.

Physalin H, physalin B, and isophysalin B suppress the quorum-sensing function of Staphylococcus aureus by binding to AgrA

The virulence of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), depends on the expression of toxins and virulence factors controlled by the quorum-sensing (QS) system, encoded on the virulence accessory gene regulator (agr) locus. The aim of this study was to identify a phytochemical that inhibits Agr-QS function and to elucidate its mechanism. We screened 577 compounds and identified physalin H, physalin B, and isophysalin B--phytochemicals belonging to physalins found in plants of the Solanaceae family--as novel Agr-QS modulators. Biological analyses and in vitro protein-DNA binding assays suggested that these physalins suppress gene expression related to the Agr-QS system by inhibiting binding of the key response regulator AgrA to the agr promoters, reducing the function of hemolytic toxins downstream of these genes in MRSA. Furthermore, although physalin F suppressed gene expression in the Agr-QS system, its anti-hemolytic activity was lower than that of physalins H, B, and isophysalin B. Conversely, five physalins isolated from the same plant with the ability to suppress Agr-QS did not reduce bacterial Agr-QS activity but inhibited AgrA binding to DNA in vitro. A docking simulation revealed that physalin interacts with the DNA-binding site of AgrA in three docking states. The carbonyl oxygens at C-1 and C-18 of physalins, which can suppress Agr-QS, were directed to residues N201 and R198 of AgrA, respectively, whereas these carbonyl oxygens of physalins, without Agr-QS suppression activity, were oriented in different directions. Next, 100-ns molecular dynamics simulations revealed that the hydrogen bond formed between the carbonyl oxygen at C-15 of physalins and L186 of AgrA functions as an anchor, sustaining the interaction between the carbonyl oxygen at C-1 of physalins and N201 of AgrA. Thus, these results suggest that physalin H, physalin B, and isophysalin B inhibit the interaction of AgrA with the agr promoters by binding to the DNA-binding site of AgrA, suppressing the Agr-QS function of S. aureus. Physalins that suppress the Agr-QS function are proposed as potential lead compounds in the anti-virulence strategy for MRSA infections.