Polyunsaturated Alkyl Amides from Echinacea: Synthesis of Diynes, Enynes, and Dienes

Biocidal efficacy of olefinic N-alkylamides against Aedes aegypti and Culex quinquefasciatus larvae

Mosquito-borne diseases are a major public-health concern worldwide. The development of resistance in mosquitoes to the existing larvicides and the associated-risks necessitates the exploration of novel molecules to control vector-borne pathogens. This study demonstrates that N-alkylamides [2E,4E-N-isobutyl-undeca-2,4-diene-8,10-diynamide (1) and 2E,4E,8Z,10E-N-isobutyl-dodeca-2,4,8,10-tetraenamide (2)] of Acmella ciliata exhibit biocidal action against Aedes aegypti and Culex quinquefasciatus larvae. The LC50 for 1 and 2 were 44.19 and 18.28 ppm against Aedes larvae, and 30.89 and 11.75 ppm against Culex larvae, respectively. We further observed that the chain length, degree of unsaturation, and terminal methylation influence the larvicidal efficacy of N-alkylamides. HPLC-assisted quantification revealed that the content of both 1 (19.01 mg/g) and 2 (68.55 mg/g) was maximum in the flowers of A. ciliata. Thus, this study concludes that N-alkylamides are promising alternatives to control mosquito larvae and can be used as standard for quantitation in test samples.

Phytochemical investigation of Asarum sieboldii var. seoulense and the phenotypic profiles of its constituents against a Parkinson's Disease olfactory cell line

Asarum sieboldii var. seoulense is a plant species under the family Aristolochiaceae and has been used for centuries as an ingredient in a well-known Traditional Chinese medicine (TCM), "Xixin", to treat symptoms of the neurodegenerative condition Parkinson's Disease (PD). Although there have been studies on the neuroprotective effect of this TCM, the phenotypic profiles of its chemical constituents against PD-implicated cellular organelles have not been reported. This research investigated the chemistry of A. sieboldii var. seoulense extract to identify the active small molecules that exhibited perturbation to the cellular compartments related to PD, potentially supporting its traditional application in treating this condition. 1H NMR-guided chemical investigation of this plant yielded twenty secondary metabolites which belong to isobutylamides, lignans and phenolics. The compounds were evaluated against an olfactory cell line derived from a PD patient using phenotypic assay. Several isolates, 2, 3, 7, 11, 13-16 and 18-20, were found to induce moderate perturbation to the staining of mitochondria, autophagosome and α-tubulin of the cells. Considering that PD pathogenesis is closely related to these cellular compartments, the results provided a rationale for the traditional application of Xixin in the treatment of PD.

Comparison of Chemical Compositions and Antioxidant Activities of Fresh and Dried Rosa roxburghii Tratt Fruit

Fresh fruit of Rosa roxburghii Tratt has attracted great interest and is used in many functional products in China. However, fresh fruits are perishable products with quite short shelf lives and few studies have focused on dried fruits. Therefore, this study aimed to explore whether the drying process can be used to preserve bioactive components of R roxburghii fruits by comparing phytochemical profiles and antioxidant activities between fresh and dried fruit. As result, a total of 95 compounds, mainly including organic acids, phenols, and flavonoids, were identified in fresh and dried fruits by using ultrahigh-performance liquid chromatography-quadrupole-time of flight mass spectrometry. The relative quantitative result showed that contents of phenols and acylamide were significantly higher ( p  < .05) in dried fruit. Furthermore, dried fruit showed stronger antioxidant activity by using 1,1-diphenyl-2-picrylhydrazyl radical scavenging ability and ferric reducing antioxidant power. This research suggested that dried R roxburghii fruit could be considered a more effective and economical health and functional source for functional food and industry.

Diastereoselective Synthesis of 1,3-Diyne-Tethered Trifluoromethylcyclopropanes through a Sulfur Ylide Mediated Cyclopropanation/DBU-Mediated Epimerization Sequence

A one-pot synthesis of 1,3-diyne-tethered trifluoromethylcyclopropanes starting from 2-CF₃-3,5-diyne-1-enes and sulfur ylides via a sulfur ylide mediated cyclopropanation and a DBU-mediated epimerization sequence is described in this work. This process is highly diastereoselective with broad substrate scope. Moreover, a series of synthetic transformations based on the diyne moieties were conducted smoothly, affording cyclopropanes featuring trifluoromethyl-substituted all-carbon quaternary centers.

γ-C (sp3)-H bond functionalisation of α,β-unsaturated amides through an umpolung strategy

The nucleophilic γ-phenylation and γ-alkylation of α,β-unsaturated amides have been developed. This umpolung reaction allows the regioselective introduction of phenyl and alkyl groups to a vinylketene N,O-acetal, which is generated in situ from an α,β-unsaturated N-alkoxyamide, followed by N-O bond cleavage in a two-step, one-pot process.

A.E.Favorskii’s scientific legacy in modern organic chemistry: prototropic acetylene – allene isomerization and the acetylene zipper reaction

Alexei Evgrafovich Favorskii was an outstanding organic chemist who left a great scientific legacy as a result of long time and fruitful work. Most of the theoretically and practically important discoveries of A.E.Favorskii were made in the chemistry of acetylene and its derivatives. Nowadays, the reactions discovered by him, which include acetylene – allene isomerization, the Favorskii and retro-Favorskii reactions, the Favorskii rearrangement and the vinylation reaction, are widely used in industry and in laboratory synthesis. This review summarizes the main scientific achievements of A.E.Favorskii, as well as their development in modern organic chemistry. Much consideration is given to acetylene – allene isomerization as a convenient method for the synthesis of methyl-substituted acetylenes and to the acetylene zipper reaction as a synthetic tool for obtaining terminal acetylenes. The review presents examples of the application of these reactions in modern organic synthesis of complex molecules, including natural compounds and their analogues.

The bibliography includes 266 references.

Improving anti-trypanosomal activity of alkamides isolated from Achillea fragrantissima

In previous studies the aerial parts of Achillea fragrantissima were found to have substantial antileishmanial and antitrypanosomal activity. A bioassay-guided fractionation of a dichloromethane extract yielded the isolation of the essential anti-trypanosomal compounds of the plant. Seven sesquiterpene lactones (including Achillolide-A), two flavonoids, chrysosplenol-D and chrysosplenetine, and four alkamides (including pellitorine) were identified. This is the first report for the isolation of the sesquiterpene lactones 3 and 4, chrysosplenetine and the group of alkamides from this plant. Bioevaluation against Trypanosoma brucei brucei TC221 (T.b brucei) using the Alamar-Blue assay revealed the novel alkamide 13 to have an IC₅₀ value of 40.37μM. A compound library, derived from the alkamide pellitorine (10), was synthesized and bioevaluated in order to find even more active substances. The most active compounds 26 and 27 showed activities in submicromolar concentrations and selectivity indices of 20.1 and 45.6, respectively, towards macrophage cell line J774.1. Toxicity of 26 and 27 was assessed using the greater wax moth Galleria mellonella larvae as an in vivo model. No significant toxicity was observed for the concentration range of 1.25-20mM.

Synthesis and biological evaluation of a series of fatty acid amides from Echinacea

Alkylamides are lipophilic constituents of Echinacea and possess numerous biological activities. Although significant effort has been focused on the study of crude Echinacea extracts, very little is known regarding the activities of the individual constituents that make up these herbal treatments. Herein we explore the SAR of simple alkylamides found in Echinacea extracts with respect to their ability to decrease the production of the pro-inflammatory mediator TNF-α. Our results have revealed the key structural requirements for activity and provide lead compounds for further investigation of these poorly understood molecules.

Unified total synthesis of the natural products endiandric acid A, kingianic acid E, and kingianins A, D, and F

A measure of the strength of a synthetic strategy is its versatility: specifically, whether it allows structurally distinct targets to be prepared. Herein we disclose a unified approach for the total synthesis of natural products of three distinct structural types, all of which occur naturally as racemic mixtures. The point of divergence involves the terminal alkylation of a conjugated tetrayne, and culminates in a significantly shortened synthesis of endiandric acid A (8 steps), the first total synthesis of kingianic acid E (8 steps), and a second-generation synthesis of kingianins A, D, and F (11 steps). Evidence for redox catalysis in the biosynthesis of kingianic acid E is presented.

Direct and two-step bioorthogonal probes for Bruton's tyrosine kinase based on ibrutinib: a comparative study

Direct and two-step activity-based probes allow for profiling of Bruton's tyrosine kinase in vitro and in situ.

Alkamides from Echinacea disrupt the fungal cell wall-membrane complex

We tested the hypothesis that alkamides from Echinacea exert antifungal activity by disrupting the fungal cell wall/membrane complex. Saccharomyces cerevisiae cells were treated separately with each of seven synthetic alkamides found in Echinacea extracts. The resulting cell wall damage and cell viability were assessed by fluorescence microscopy after mild sonication. Membrane disrupting properties of test compounds were studied using liposomes encapsulating carboxyfluorescein. Negative controls included hygromycin and nourseothricin (aminoglycosides that inhibit protein synthesis), and the positive control used was caspofungin (an echinocandin that disrupts fungal cell walls). The results show that yeast cells exposed to sub-inhibitory concentrations of each of the seven alkamides and Echinacea extract exhibit increased frequencies of cell wall damage and death that were comparable to caspofungin and significantly greater than negative controls. Consistent with effects of cell wall damaging agents, the growth inhibition by three representative alkamides tested and caspofungin, but not hygromycin B, were partially reversed in sorbitol protection assays. Membrane disruption assays showed that the Echinacea extract and alkamides have pronounced membrane disruption activity, in contrast to caspofungin and other controls that all had little effect on membrane stability. A Quantitative Structure-Activity Relationship (QSAR) analysis was performed to study the effect of structural substituents on the antifungal activity of the alkamides. Among the set studied, diynoic alkamides showed the greatest antifungal and cell wall disruption activities while an opposite trend was observed in the membrane disruption assay where the dienoic group was more effective. We propose that alkamides found in Echinacea act synergistically to disrupt the fungal cell wall/membrane complex, an excellent target for specific inhibition of fungal pathogens. Structure-function relationships provide opportunities for synthesis of alkamide analogs with improved antifungal activities.

Iron-catalyzed aerobic oxidation of allylic alcohols: the issue of C═C bond isomerization

An aerobic oxidation of allylic alcohols using Fe(NO3)3·9H2O/TEMPO/NaCl as catalysts under atmospheric pressure of oxygen at room temperature was developed. This eco-friendly and mild protocol provides a convenient pathway to the synthesis of stereodefined α,β-unsaturated enals or enones with the retention of the C-C double-bond configuration.