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Quinolizidomycins A ( 1 ) and B ( 2 ), two unprecedented quinolizidine alkaloids featuring a tricyclic 6/6/5 ring system, were isolated from Streptomyces sp. KIB-1714. Their structures were assigned by detailed spectroscopic data analyses and X-ray diffraction. Stable isotope labeling experiments suggested that compounds 1 and 2 are derived from lysine, ribose 5-phosphate, and acetate units, which indicates an unprecedented manner of assembly of the quinolizidine (1-azabicyclo[4.4.0]decane) scaffold in quinolizidomycin biosynthesis. Quinolizidomycin A ( 1 ) was active in an acetylcholinesterase inhibitory assay.

Inflammation is connected with a variety of diseases and there is still a need to develop more effective and safer anti-inflammatory drugs. Herein, we synthesized, resolved, and characterized eight enantiopure isomers of yaequinolone J1 (1), yaequinolone J2 (2), 4'-desmethoxyyaequinolone J1 (3), and 4'-desmethoxyyaequinolone J2 (4). The key synthetic steps were extended and 34 racemic analogues modified at the 4-aryl, the N-position, and the pyran ring were designed and synthesized. All the synthesized compounds were evaluated for their anti-inflammatory activities in RAW 264.7 cells of which 13 compounds showed significant inhibition of nitric oxide (NO) production at a concentration of 0.1 μM, which was more potent than that of indomethacin. Furthermore, compounds (-)-3, (-)-4, 5h, and 6g reduced the production of IL-6 in LPS-stimulated RAW 264.7 cells at a concentration of 50 nM. A preliminary SAR indicated that 3'-Br (5h), 4'-NO 2 (6g) on 4-phenyl and 3-bromobenzyl (7f) on the N-position were the most effective substituents. This is the first report of the anti-inflammatory yaequinolone alkaloids and the present study provided evidence for exploiting this series of highly efficacious derivatives for new anti-inflammatory agents., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)

Two new steroidal alkaloids (1-2), together with seven known related steroidal alkaloids (3-9), were isolated from the rhizomes of Veratrum nigrum L. Their structures were elucidated by extensive spectroscopic analysis, and by comparison with literature data. Compound 1 possessed a rare 1, 3-oxazolidine unit within varazine-type alkaloids, and 2 was a 9-hydroxy-4-one derivative of 3-veratroylgermine. All isolates were evaluated inhibit tomato yellow leaf curl virus (TYLCV) activity. Compounds 5 and 7 (40 μg/mL) showed a significant anti-TYLCV activity in the host Nicotiana benthamiana with inhibition rates 74.6% and 63.4%, respectively, which are higher than that of the positive control ningnanmycin (51.4%)., (Copyright © 2020. Published by Elsevier B.V.)

Four new Myrioneuron alkaloids, mysumamides A-D (1-4), along with three known ones were isolated from the twigs and leaves of Myrioneuron effusum. All of these alkaloids possessed the tetracyclic skeleton and contained the decahydroquinoline (cis-DHQ) moiety. Their structures and relative configurations were elucidated on the basis of spectroscopic methods, especially 2D NMR techniques. The absolute configuration of 1 was determined by single-crystal X-ray diffraction. The cytotoxic activities of these compounds were also evaluated in vitro., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Investigation of the alkaloids from Myrioneuron faberi, a plant unique to China, gave four pairs of enantiomers (1-4). (±)-β-Myrifabral A (1) and (±)-α-myrifabral A (2) formed an inseparable mixture of anomers (cluster A), as did (±)-β-myrifabral B (3) and (±)-α-myrifabral B (4) (cluster B). Their structures were determined by X-ray diffraction and NMR analysis. Compounds 1-4 possessed novel cyclohexane-fused octahydroquinolizine skeletons and represent the first quinolizidine alkaloids from the genus Myrioneuron. The epimers of cluster A (1 and 2) were modified and separated. In vitro, clusters A and B and their derivatives inhibited replication of hepatitis C virus (HCV, IC50 0.9 to 4.7 μM) with cytotoxicity lower than that of telaprevir.

One Myrioneuron alkaloid, myrifabine (1), the first example of a dimer with 12 chiral centers embraced in a decacyclic novel skeleton, was isolated from Myrioneuron faberi . Its structure was elucidated by spectroscopic data and single-crystal X-ray diffraction. The antimicrobial and cytotoxic activities of 1 were evaluated in vitro.

Five new yuzurimine-type Daphniphyllum alkaloids, daphmacromines K-O (1-5), were isolated from the leaves and stems of Daphniphyllum macropodum. Their structures were elucidated by extensive spectroscopic techniques, including 2D NMR spectroscopy and mass spectrometry. Daphmacromine O (5) showed moderate cytotoxic activity against brine shrimp., (Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.)

A new BIS-1-oxaquinolizidine alkaloid, 9'- EPI-3 β,3' β-dimethylxestospongin C (2), and three known related analogues have been isolated from the Hainan sponge Neopetrosia exigua., (© Georg Thieme Verlag KG Stuttgart · New York.)

A new pyrrolyl 4-quinolinone alkaloid with an unprecedented ring system, named penicinoline (1) was isolated from a mangrove endophytic fungus. The structure of 1 was elucidated by spectroscopic methods and comparison with its derivative, penicinotam (1a), an unexpected lactam that was obtained from 1 by intramolecular dehydration. The structure of 1a was unambiguously confirmed by single-crystal X-ray analysis. Penicinoline (1) showed potent in vitro cytotoxicity toward 95-D and HepG2 cell lines with IC(50) values of 0.57 and 6.5 microg/mL, respectively., (Copyright 2010 Elsevier Ltd. All rights reserved.)

Two new Daphniphyllum alkaloids, macropodumines J and K (1 and 2, resp.), together with six known structurally related alkaloids, 3-8, were isolated from the bark of Daphniphyllum macropodum M(IQ). The structures of the new compounds 1 and 2 were elucidated on the basis of a comprehensive analysis of their spectroscopic and chemical data. Macropodumine J (1) contains a CN group which is relatively rare in naturally occurring alkaloids. All isolated compounds were tested for their insecticidal activities against a number of insect species. Daphtenidine C (5) is the most active compound against Plutella xylostella. This is the first report of insecticidal properties of Daphniphyllum alkaloids.

Ergot alkaloids (EAs) are a diverse group of indole alkaloids known for their complex structures, significant pharmacological effects, and toxicity to plants. The biosynthesis of these compounds begins with chanoclavine-I aldehyde (CC aldehyde, 2), an important intermediate produced by the enzyme EasDaf or its counterpart FgaDH from chanoclavine-I (CC, 1). However, how CC aldehyde 2 is converted to chanoclavine-I acid (CC acid, 3), first isolated from Ipomoea violacea several decades ago, is still unclear. In this study, we provide in vitro biochemical evidence showing that EasDaf not only converts CC 1 to CC aldehyde 2 but also directly transforms CC 1 into CC acid 3 through two sequential oxidations. Molecular docking and site-directed mutagenesis experiments confirmed the crucial role of two amino acids, Y166 and S153, within the active site, which suggests that Y166 acts as a general base for hydride transfer, while S153 facilitates proton transfer, thereby increasing the acidity of the reaction. Key points: •EAs possess complicated skeletons and are widely used in several clinical diseases •EasDafbelongs to the short-chain dehydrogenases/reductases (SDRs) and converted CC or CC aldehyde to CC acid •The catalytic mechanism of EasDaffor dehydrogenation was analyzed by molecular docking and site mutations [ABSTRACT FROM AUTHOR]

Natural products are well established as an important resource and play an important role in drug discovery. Here, two pyrrolinone-fused benzoazepine alkaloids, (+)-asperazepanones A (1) and B (2) with a 6/7/5 ring system, together with the artifact (−)-asperazepanone A (1), were isolated from the coral-derived Aspergillus candidus fungus. Their structures including absolute configurations were elucidated by extensive spectroscopic methods, single crystal X-ray diffraction, and ECD calculations. Furthermore, total syntheses of (±)-1 and (±)-2 have been achieved starting from the commercially L-aspartic acid diethyl ester hydrochloride and monoethyl malonate in 7 and 8 steps, respectively. The key step in the syntheses was an intramolecular Friedel-Crafts reaction to build the unique tricyclic skeleton. Interestingly, (+)-2 not only showed obviously inhibitory activity against NO production, but also inhibited potent LPS-induced expression of TNF-α and IL-6 at the concentration of 0.1 μM. It thus represents a potentially promising lead for anti-inflammatory drug discovery. Benzoazepine is a well-known pharmacophore presented in several marketed drugs. Here, the authors report the isolation and total syntheses of asperazepanones A and B from coral-derived Aspergillus candidus, two novel pyrrolinone-fused benzoazepine alkaloids with potent anti-inflammatory activities. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Two new bis‐quinolizidine alkaloids, neopetrosiasins A (1) and B (2), possessing cis‐ and trans‐quinolizidine nuclei, one known related analogue petrosin (3) and three known xestospongins (4—6), were isolated from the South China Sea sponge Neopetrosia chaliniformis. The structures of new compounds were unambiguously determined by extensive spectroscopic and single‐crystal X‐ray analyses. In bioassay, compounds 4—6 exhibited moderate cytotoxicity against several human cancer cells. [ABSTRACT FROM AUTHOR]

Abstract: A novel securinega alkaloid, suffruticosine (1), was isolated from the leaves and barks of Securinega suffruticosa. The structure of 1, characterized by a fused complex octacyclic system, was elucidated by combined spectroscopic techniques, especially 2D NMR and CD spectral analyses. [Copyright &y& Elsevier]

isolation and structure elucidation [ABSTRACT FROM AUTHOR]