A new benzophenanthridine alkaloid from stem bark of Zanthoxylum rhetsa and its biological activities

A new benzophenanthridine alkaloid 6-butanoyldihydrochelerythrine (1) and five known alkaloids 6-acetonyldihydronitidine (2), 6-acetonyldihydrochelerythrine (3), isocorydine (4), (O)-methyltembamide (5), N-(4-methoxyphenethyl)benzamide (6) were isolated from the stem barks of Zanthoxylum rhetsa. These structures were elucidated by 1D, 2D NMR spectroscopy and by mass spectrometry. This is the first time that compounds 2-6 were identified from Zanthoxylum rhetsa and the first time that compounds 4 and 6 were identified from the genus Zanthoxylum. Bioactivity results of isolated compounds showed that 1, 2, 5 and 6 exhibited inhibitory activity against MCF7 and A549 cell lines, while 3 showed the inhibitory activity against A549 cell line; all isolated compounds 1-6 inhibited at least two strain microorganisms; compound 4 showed angiotensin II converting enzyme inhibitory activity in vitro with IC50 value of 65.58 µM and in silico with a docking score of -11.52 kcal/mol.

Transition Metal-Free Regioselective Phosphonation of Pyridines: Scope and Mechanism

Regioselective phosphonation of pyridines is an interesting transformation in synthesis and medicinal chemistry. We report herein a metal-free approach enabling access to various 4-phosphonated pyridines. The method consists of simply activating the pyridine ring with a Lewis acid (BF₃·OEt₂) to facilitate the nucleophilic addition of a phosphine oxide anion. The formed sigma complex is subsequently oxidized with an organic oxidant (chloranil) to yield the desired adducts in good to excellent yields. We furthermore showed that access to C2-phosphoinated pyridines can be achieved in certain cases with strong Lewis basic phosphorus nucleophiles or with strong Lewis acidic pyridines. Both experimental and computational mechanistic investigations were undertaken and allowed us to understand the factors controlling the reactivity and selectivity of this reaction.

Inhibition of Arenaviridae nucleoprotein exonuclease by bisphosphonate

Arenaviruses are emerging enveloped negative-sense RNA viruses that cause neurological and hemorrhagic diseases in humans. Currently, no FDA-approved vaccine or therapeutic agent is available except for ribavirin, which must be administered early during infection for optimum efficacy. A hallmark of arenavirus infection is rapid and efficient immune suppression mediated by the exonuclease domain encoded by the nucleoprotein. This exonuclease is therefore an attractive target for the design of novel antiviral drugs since exonuclease inhibitors might not only have a direct effect on the enzyme but could also boost viral clearance through stimulation of the innate immune system of the host cell. Here, in silico screening and an enzymatic assay were used to identify a novel, specific but weak inhibitor of the arenavirus exonuclease, with IC₅₀ values of 65.9 and 68.6 µM for Mopeia virus and Lymphocytic choriomeningitis virus, respectively. This finding was further characterized using crystallographic and docking approaches. This study serves as a proof of concept and may have assigned a new therapeutic purpose for the bisphosphonate family, therefore paving the way for the development of inhibitors against Arenaviridae.

Observation of arenavirus nucleoprotein heptamer assembly

Arenaviruses are enveloped viruses containing a segmented, negative, and ambisense single‐stranded RNA genome wrapped with a nucleoprotein (NP). The NP is the most abundant viral protein in infected cells and plays a critical role in both replication/transcription and virion assembly. The NP associates with RNA to form a ribonucleoprotein (RNP) complex, and this implies self‐assembly while the exact structure of this polymer is not yet known. Here, we report a measurement of the full‐length Mopeia virus NP by negative stain transmission electron microscopy. We observed RNP complex particles with diameter 15 ± 1 nm as well as symmetric circular heptamers of the same diameter, consistent with previous observations.

Alkaloids From Zanthoxylum nitidum and Their Cytotoxic Activity

Zanthoxylum nitidum (Roxb.) DC (Rutaceae) is a traditional medicine used for the treatment of various diseases like toothache, gingivitis, fever, colic vomiting, diarrhea, and cholera. Three new alkaloids, zanthocadinanine C (1), 7-methoxy-8-demethoxynitidine (2), and zanthonitiside I (3) were isolated from the stems and twigs of Z. nitidum. Their structures were determined on the basis of extensive spectroscopic, including 1-dimensional and 2-dimensional nuclear magnetic resonance and mass spectroscopy data. Compounds 1–3 were evaluated for cytotoxic activity against 5 human cancer cell lines, KB, MCF-7, LNCaP, HepG-2, and LU-1. Compound 2 showed significant cytotoxic activity against all tested human cancer cell lines with IC50 values ranging from 10.3 to 12.6 µM.

Structure and oligomerization state of the C-terminal region of the Middle East respiratory syndrome coronavirus nucleoprotein

Middle East respiratory syndrome coronavirus (MERS-CoV) is a human pathogen responsible for a severe respiratory illness that emerged in 2012. Structural information about the proteins that constitute the viral particle is scarce. In order to contribute to a better understanding of the nucleoprotein (N) in charge of RNA genome encapsidation, the structure of the C-terminal domain of N from MERS-CoV obtained using single-crystal X-ray diffraction is reported here at 1.97 Å resolution. The molecule is present as a dimer in the crystal structure and this oligomerization state is confirmed in solution, as measured by additional methods including small-angle X-ray scattering measurements. Comparisons with the structures of the C-terminal domains of N from other coronaviruses reveals a high degree of structural conservation despite low sequence conservation, and differences in electrostatic potential at the surface of the protein.

Chemical components of Ardisia splendens leaves and their activity against coxsackie A16 viruses

Using a combination of chromatographic methods, one new flavonol glycoside, myricetin 3,7-di-O-alpha-L-rhamnopyranoside (1), and nine known compounds myricitrin (2), quercetin 3,7-di-O-alpha-L-rhamnopyranoside (3), quercitrin (4), desmanthin-l (5), myricetin 3-O-(3"-O-galloyl)-alpha-L-rhamnopyranoside (6), (+)-catechin (7), benzyl O-1-D-glucopyranoside (8), 2-phenylethyl O-beta-D-glucopyranoside (9), and corilagin (10) were isolated from the leaves of Ardisia splendens Pit. Based on an in vitro test against Coxsackie viruses A16 by SRB assay, only compounds 2, 5, and 10 exhibited activity against Coxsackie viruses A16 with IC50 values of 40.1, 32.2, and 30.5 microM, respectively. This result suggested that compounds 2, 5, and 10 might be potential agents for treating hand, foot and mouth diseases.

Chemical constituents of the fruits of Gleditschia australis Hemsl

From the methanolic extract of the fruits of Gleditschia australis Hemsl., a new flavonoid derivative 3"-O-menthiafoloylisovitexin (1) and a new carbohydrate ester of cinnamic acid 1-O-E-cinnamoyl-[2-O-E-cinnamoyl-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranoside] (2) have been isolated along with four known compounds, 1-O-E-cinnamoyl-[3-O-E-cinnamoyl-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranoside], isovitexin, luteolin, and quercetin. Their structures were elucidated on the basis of physical and spectroscopic evidence.

Synthesis of 4,5-Benzotropones by Cyclization of 1,3-Bis-Silyl Enol Ethers with 1,2-Dialdehydes

The cyclization of 1,3-bis-silyl enol ethers or (2,4-dioxobutylidene)triphenylphosphoranes with phthalic dialdehyde allowed a convenient synthesis of a variety of 4,5-benzotropones. The hydrogenation of benzotropones afforded functionalized benzocycloheptanones which were transformed into tricyclic butenolides.