Arbolodinines A−C, biologically-active aspidofractinine-aspidofractinine, aspidofractinine-strychnan, and kopsine-strychnan bisindole alkaloids from Kopsia arborea

Structural diversity and chemical logic underlying the assembly of monoterpene indole alkaloids oligomers

Covering: up to 2024This review aims to draw a parallel between all known oligomers of monoterpene indole alkaloids (MIAs) by illustrating the chemical logic underlying their assembly. For this purpose, oligomeric MIAs were first comprehensively listed and organized according to the names of the backbones of their constitutive monomers and the binding sites. From this extensive list, an oligomer network was generated and unprecedented MIA statistics were mined and shared herein. Subsequently, oligomeric MIAs were categorized according to the number of connections instigated between their monomeric components (single, double, triple, and mixed tethering), then subdivided according to the uniqueness or combination of oligomerization assembly reactions. This effort outlined oligomerization trends in a scaffold-specific manner, and established binding reactivity patterns facilitating the comprehension of the associated biosynthetic processes. At last, this review illustrates a unique initiative in crafting a comprehensive repository of machine-readable metadata for MIA oligomers that could be leveraged for chemoinformatic purposes.

Intramolecular through-space NMR spectroscopic effect of steric compression on 1H NMR spectroscopy

The intramolecular through-space NMR spectroscopic effect of steric compression is related to intramolecular through-space van der Waals repulsion. The electron cloud of a proton can be pushed away by the electron cloud of a nearby proton or functional group. As the electron population of the sterically compressed proton is decreased (therefore deshielded), the chemical shift sharply moves downfield, which may result in ambiguity for the proton signal assignment. Also, the conformation of the local area of the sterically compressed proton can be altered by the steric repulsion, therefore, the coupling constant/coupling pattern of a sterically compressed proton could be influenced. This review summarizes and presents the impacts on the chemical shift and coupling constant by the 1H NMR spectroscopic effect of steric compression extracted from the reported examples from the 1950s to 2021.

Influence of Ring Strain on the Formation of Rearrangement vs Cyclization Isotwistane Products in the Acyl Radical Reaction of Bicyclo[2.2.2]octanone

An acyl radical reaction of bicyclo[2.2.2]octenone to yield either rearranged or cyclized isotwistane products is described. The influence of ring strain on the reaction was demonstrated by alternating the sizes of the fused ring in the starting material. DFT calculations showed that the reaction is under thermodynamic control and proceeds via a 5-exo-trig cyclization intermediate, which undergoes either hydrogen-atom transfer (HAT) to give a cyclized product or rearrangement via a twistane intermediate to give a rearranged product.

Bisindole natural products: A vital source for the development of new anticancer drugs

Currently, the number of new cancer cases and deaths worldwide is increasing year on year. In addition to the requirement for cancer prevention, the top priority is still to seek the effective cure of cancer. In over a half century of constant exploration, increasing attention has been paid to the excellent anticancer activity of natural products, with more and more natural products isolated, identified and detected. For this study, the focus lies the natural products of bisindole, where two indole molecules are indirectly linked or directly polymerized, developing the diversity of structure and mechanism, accompanied with the better anticancer activity than monomers. There has been a long history of applying indirubin and vincristine in cancer treatment, verifying the anticancer effect of bisindoles. Vincribine, midostaurin and other anticancer drugs have also been developed and commercialized. In this paper, a review regarding the potential therapeutic effect of bisindole alkaloids extracted from various natural products was carried out, in which the progress made in research of 242 bisindole alkaloids for cancer treatment was introduced. These compounds may be applicable as medicinal products for clinical research in the future.

Monoterpenoid indole alkaloid dimers from Kopsia arborea inhibit cyclin-dependent kinase 5 and tau phosphorylation

Three undescribed monoterpenoid indole alkaloid dimers (kopoffines A-C, which are connected via a methylene unit) and with nine known alkaloids were isolated and identified from the fruits of Kopsia arborea Blume. Their structures, including their absolute configurations, were established by HRESIMS, NMR, single-crystal X-ray diffraction, and ECD analyses. Kopoffines A-C showed significant inhibition against cyclin-dependent kinase 5 (IC₅₀: 0.34-2.18 μM). Western blotting analyses showed that kopoffines A-C significantly decreased the protein levels of CDK5 and phospho-CDK5 (Tyr15) (pCDK5) at concentrations of 2.5 and 10 μM. The levels of phospho-Tau (Thr217) (pTau217, a new biomarker of AD), and phospho-Tau (Ser396) (pTau396), which play major roles in the formation of neurofibrillary tangles , were decreased by the kopoffines A-C treatment. Molecular docking studies indicated that kopoffines A-C could form stable interactions with CDK5.

A comprehensive review on phytochemistry and pharmacology of genus Kopsia: monoterpene alkaloids - major secondary metabolites

Kopsia belongs to the family Apocynaceae, which was originally classified as a genus in 1823. Kopsia consists of medicinal plants that can be traditionally used to treat rheumatoid arthritis, pharyngitis, tonsillitis, and dropsy. More than one hundred and twenty-five publications have been documented relating to the phytochemical and pharmacological results, but a systematic review is not available. The goal of this study is to compile almost all of the secondary metabolites from the plants of genus Kopsia, as well as the coverage of their pharmacological research. The document findings were conducted via reliable sources, including Web of Science, Sci-Finder, Science Direct, PubMed, Google Scholar, and publishers, while four words "Kopsia", "monoterpene alkaloids", "Phytochemistry" and "Pharmacology" are key factors to search for references. Most Kopsia secondary metabolites were collected. A total of four hundred and seventy-two, including four hundred and sixty-six monoterpene alkaloids, five triterpenoids, and one sterol, were summarized, along with their resource. Kopsia monoterpene alkaloids presented in various skeletons, but aspidofractinines, eburnamines, and chanofruticosinates are the three major backbones. Mersinines and pauciflorines are new chemical classes of monoterpene alkaloids. With the rich content of monoterpene alkaloids, Kopsia constituents were also the main objects in pharmacological studies since the plant extracts and isolated compounds were proposed for anti-microbial, anti-inflammatory, anti-allergic, anti-diabetic, anti-manic, anti-nociceptive, acetylcholinesterase (AChE) inhibitory, cardiovascular, and vasorelaxant activities, especially cytotoxicity.

Anti-inflammatory and analgesic monoterpenoid indole alkaloids of Kopsia officinalis

ETHNOPHARMACOLOGICAL RELEVANCE

"Ya gai", an important part of Dai medical theory, is traditionally recognized as an antidote. Kopsia officinalis Tsiang et P. T. Li is a "Ya gai" related medicine and has been widely used by Dai people for the treatment of pain and inflammation. Previous literature on title species suggested that monoterpenoid indole alkaloids (MIAs) could be its main bioactive components. However, the specific bioactive ingredients for inflammation-related treatment are still unrevealed, which inspired us to conduct a phytochemical and pharmacological investigation related to its traditional use.

AIM OF THE STUDY

To support the traditional use of K. officinalis by assessing the anti-inflammatory and analgesic effects of its purified MIAs.

MATERIAL AND METHODS

Compounds were isolated and purified from the barks and leaves of K. officinalis using diverse chromatographic methods. The structures were established by means of extensive spectroscopic analyses and quantum computational technique. The anti-inflammatory activities of the purified MIAs were evaluated in vitro based on the suppression of lipopolysaccharide-activated inflammatory mediators (COX-2, IL-1β, and TNF-α) in RAW 264.7 macrophage cells. Anti-inflammatory and analgesic activities in vivo were assessed with carrageenan-induced paw edema and acetic acid-stimulated writhing in mice models.

RESULTS

23 MIAs including four new compounds were obtained and structurally established. Most of isolates showed significant anti-inflammatory effects in vitro by inhibiting inflammatory mediators (COX-2, IL-1β, and TNF-α). Further pharmacological evaluation in vivo revealed that 12-hydroxy-19(R)-hydroxy-ibophyllidine (1) and 11,12-methylenedioxykopsinaline N⁴-oxide (5) remarkably decreased the number of writhing, while kopsinic acid (8), (-)-kopsinilam (12), and normavacurine-21-one (20) significantly relieved paw edema, respectively, even better than the positive control aspirin.

CONCLUSIONS

The in vitro and in vivo findings supported the traditional use of K. officinalis with respect to its anti-inflammatory and analgesic effect, as well as provided potent bioactive MIAs for further chemical modification and pharmacological investigation.

Monoterpene indole alkaloids from Vinca minor L. (Apocynaceae): Identification of new structural scaffold for treatment of Alzheimer's disease

One undescribed indole alkaloid together with twenty-two known compounds have been isolated from aerial parts of Vinca minor L. (Apocynaceae). The chemical structures of the isolated alkaloids were determined by a combination of MS, HRMS, 1D, and 2D NMR techniques, and by comparison with literature data. The NMR data of several alkaloids have been revised, corrected, and missing data have been supplemented. Alkaloids isolated in sufficient quantity were screened for their in vitro acetylcholinesterase (AChE; E.C. 3.1.1.7) and butyrylcholinesterase (BuChE; E.C. 3.1.1.8) inhibitory activity. Selected compounds were also evaluated for prolyl oligopeptidase (POP; E.C. 3.4.21.26), and glycogen synthase 3β-kinase (GSK-3β; E.C. 2.7.11.26) inhibition potential. Significant hBuChE inhibition activity has been shown by (-)-2-ethyl-3[2-(3-ethylpiperidinyl)-ethyl]-1H-indole with an IC₅₀ value of 0.65 ± 0.16 μM. This compound was further studied by enzyme kinetics, along with in silico techniques, to reveal the mode of inhibition. This compound is also predicted to cross the blood-brain barrier (BBB) through passive diffusion.