Tabernaesines A-I, Cytotoxic Aspidosperma-Aspidosperma-Type Bisindole Alkaloids from Tabernaemontana pachysiphon

Globospiramine from Voacanga globosa Exerts Robust Cytotoxic and Antiproliferative Activities on Cancer Cells by Inducing Caspase-Dependent Apoptosis in A549 Cells and Inhibiting MAPK14 (p38α): In Vitro and Computational Investigations

Bisindole alkaloids are a source of inspiration for the design and discovery of new-generation anticancer agents. In this study, we investigated the cytotoxic and antiproliferative activities of three spirobisindole alkaloids from the traditional anticancer Philippine medicinal plant Voacanga globosa, along with their mechanisms of action. Thus, the alkaloids globospiramine (1), deoxyvobtusine (2), and vobtusine lactone (3) showed in vitro cytotoxicity and antiproliferative activities against the tested cell lines (L929, KB3.1, A431, MCF-7, A549, PC-3, and SKOV-3) using MTT and CellTiter-Blue assays. Globospiramine (1) was also screened against a panel of breast cancer cell lines using the sulforhodamine B (SRB) assay and showed moderate cytotoxicity. It also promoted the activation of apoptotic effector caspases 3 and 7 using Caspase-Glo 3/7 and CellEvent-3/7 apoptosis assays. Increased expressions of cleaved caspase 3 and PARP in A549 cells treated with 1 were also observed. Apoptotic activity was also confirmed when globospiramine (1) failed to promote the rapid loss of membrane integrity according to the HeLa cell membrane permeability assay. Network pharmacology analysis, molecular docking, and molecular dynamics simulations identified MAPK14 (p38α), a pharmacological target leading to cancer cell apoptosis, as a putative target. Low toxicity risks and favorable drug-likeness were also predicted for 1. Overall, our study demonstrated the anticancer potentials and apoptotic mechanisms of globospiramine (1), validating the traditional medicinal use of Voacanga globosa.

Discovery of plant-derived anti-tumor natural products: Potential leads for anti-tumor drug discovery

Natural products represent a paramount source of novel drugs. Numerous plant-derived natural products have demonstrated potent anti-tumor properties, thereby garnering considerable interest in their potential as anti-tumor drugs. This review compiles an overview of 242 recently discovered natural products, spanning the period from 2018 to the present. These natural products, which include 69 terpenoids, 42 alkaloids, 39 flavonoids, 21 steroids, 14 phenylpropanoids, 5 quinolines and 52 other compounds, are characterized by their respective chemical structures, anti-tumor activities, and mechanisms of action. By providing an essential reference and fresh insights, this review aims to support and inspire researchers engaged in the fields of natural products and anti-tumor drug discovery.

Diverse aspidosperma-type alkaloids from the leaves of Tabernaemontana bovina with anti-hepatoma activity

Seventeen undescribed Aspidosperma-type alkaloids (ASPs), along with nine known ones were isolated from the leaves of Tabernaemontana bovina. Taberbovermines A and B were assigned to tabersonine-type with a contracted A- and E-ring, respectively. Taberbovermine C was attributed to tabersonine without D ring. These structures of the ASPs were established on the basis of comprehensive spectroscopic data, electronic circular dichroism calculations and X-ray diffraction. The summaries of structure-activity relationship of tabersonine class were discussed based on hepatoma cells screening.

Two new antimicrobial monoterpenoid indole alkaloids from the roots of Rauvolfia yunnanensis

Two new monoterpenoid indole alkaloids 3-hydroxylochnerine (1) and 10-hydroxyvinorine (2) were isolated from the roots of Rauvolfia yunnanensis. Their structures were elucidated based on the analysis of spectroscopic data and ECD calculation. Both compounds exhibited potent antimicrobial activity against Bacillus subtilis and Escherichia coli, and their activities were comparable to the well-known antibacterial drug berberine.

Two new monoterpenoid indole alkaloids from the kernels of Kopsia arborea

Two new monoterpenoid indole alkaloids, (2 R, 7 R, 16 R, 20 R, 21S)-12-hydroxypleiocarpine (1) and (2S, 7 R, 16S, 20 R, 21S)-N-methoxycarbonyl-11,12-methylenedioxy-Δ^14,15-kopsinaline (2), along with six known alkaloids were isolated from the methanol extract of the kernels of Kopsia arborea. Their structures including the absolute configurations were elucidated by HRESIMS, NMR spectroscopy, and quantum computational methods. Their cytotoxicity against two human cancer cell lines were also evaluated.

The current scenario of naturally occurring indole alkaloids with anticancer potential

Naturally occurring indole alkaloids are ubiquitously present in nature and possess extensive biological properties and structural diversity. Mechanistically, naturally occurring indole alkaloids have the potential to inhibit cancer cell proliferation, arrest cell cycle and induce apoptosis. Accordingly, naturally occurring indole alkaloids exhibit promising activity against both drug-sensitive and drug-resistant cancers including multidrug-resistant forms. Therefore, naturally occurring indole alkaloids constitute an important source of anticancer drug leads and candidates. The goal of this review is to highlight the current scenario of naturally occurring indole alkaloids with anticancer potential, covering articles published from 2018 to present. The names, sources, and antiproliferative activity are discussed to continuously open up a map for the remarkable exploration of more effective candidates.

Indole-Containing Natural Products 2019-2022: Isolations, Reappraisals, Syntheses, and Biological Activities

Indole alkaloids represent a large subset of natural products, with more than 4100 known compounds. The majority of these alkaloids are biologically active, with some exhibiting excellent antitumor, antibacterial, antiviral, antifungal, and antiplasmodial activities. Consequently, the natural products of this class have attracted considerable attention as potential leads for novel therapeutics and are routinely isolated, characterized, and profiled to gauge their biological potential. However, data on indole alkaloids, their various structures, and bioactivities are complex due to their diverse sources, such as plants, fungi, bacteria, sponges, tunicates, and bryozoans; thus, isolation methods produce an incredible trove of information. The situation is exacerbated when synthetic derivatives, as well as their structures, bioactivities, and synthetic schemes, are considered. Thus, to make such data comprehensive and inform researchers about the current field's state, this review summarizes recent reports on novel indole alkaloids. It deals with the isolation and characterization of 250 novel indole alkaloids, a reappraisal of previously reported compounds, and total syntheses of indole alkaloids. In addition, several syntheses and semi-syntheses of indole-containing derivatives and their bioactivities are reported between January 2019 and July 2022.

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.

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.

Two new aspidosperma-type monoterpenoid indole alkaloids from Ervatamia officinalis

Two new aspidosperma-type monoterpenoid indole alkaloids, 16-O-methylvoafinine (1) and 14,15-diepi-voafinidine (2) were isolated from the aerial parts of Ervatamia officinalis. Their structures were established by comprehensive spectroscopic analysis including 1D and 2D NMR, HR-ESI-MS, and electronic circular dichroism calculation. The isolated compounds were evaluated for cytotoxic activities against HepG2, MCF-7, and A549 cell lines by CCK-8 assay.

Taberdines L and M, two new alkaloids from Tabernaemontana divaricata

Two new alkaloids, taberdines L (1) and M (2), together with six known alkaloids, were isolated from the twigs and leaves of Tabernaemontana divaricata. Taberdine L (1) represents the first optically active natural member of the allo iboga class of alkaloids with the ethyl side chain in a bridgehead position. Their structures including absolute configuration were elucidated by a combination of MS, NMR, and ECD calculation. The in vitro cytotoxic activities of 1 and 2 against five human cancer cell lines were also evaluated.

Aspidosperma and Strychnos alkaloids: Chemistry and biology

Of Nature's nearly 3000 unique monoterpene indole alkaloids derived from tryptophan, those members belonging to the Aspidosperma and Strychnos families continue to impact the fields of natural products (i.e., isolation, structure determination, biosynthesis) and organic chemistry (i.e., chemical synthesis, methodology development) among others. This review covers the biological activity (Section 2), biosynthesis (Section 3), and synthesis of both classical and novel Aspidosperma (Section 4), Strychnos (Section 5), and selected bis-indole (Section 6) alkaloids. Technological advancements in genetic sequencing and bioinformatics have deepened our understanding of how Nature assembles these intriguing molecules. The proliferation of innovative synthetic strategies and tactics for the synthesis of the alkaloids covered in this review, which include contributions from over fifty research groups from around the world, are a testament to the creative power and technical skills of synthetic organic chemists. To be sure, Nature-the Supreme molecular architect and source of a dazzling array of irresistible chemical logic puzzles-continues to inspire scientists across multiple disciplines and will certainly continue to do so for the foreseeable future.

Lignans with (N, N-diethyl)methyl amino group from Buxus rugulosa

Buxrugulosides A-E, four lignan glycosides (1-4) and a protocatechuate derivative (5) featuring a rare (N, N-diethyl)methyl amino group at aromatic rings, were obtained from the aerial parts of Buxus rugulosa, which is famous for treating coronary heart disease. Their structures including absolute configurations were elucidated by HRMS, 1D and 2D NMR, and by comparing their CD data with previous reports. Compound 1 was a rare sesquilignan, and all of these compounds were the first example of lignans with (N, N-diethyl)methyl amino group.

Trimeric and dimeric Aspidosperma-type alkaloids from leaves of Tabernaemontana divaricata 'Dwaft'

Continued interest in bioactive monoterpenoid indole alkaloids and the purpose to explore the artificial cultivation influence on the chemical composition in the same plant species, 8 undescribed Aspidosperma-type alkaloids including two unprecedented trimers, taberdivarines A-B (1-2), and six new dimers, taberdivarines CH (3-8), together with 9 known bisindoles were isolated from the leaves of Tabernaemontana divaricata 'Dwaft'. Notably, taberdivarines A and B were the first cases of Aspidosperma-Aspidosperma-Aspidosperma-type alkaloids with furan ring linkage patterns of the natural products. Their structures were elucidated by comprehensive spectroscopic analyse. Compounds 1-8 were screened for the cytotoxicity against three human cancer cell lines, SMMC-7721, HT-29 and A549. Among them, Compound 6 exhibited significant activity against three cell lines with IC₅₀ values of 0.30, 0.75 and 3.41 μM, respectively (IC₅₀ = 3.02, 0.14 and 2.23 μM for the positive control, vinorelbine). Compound 1, 3, 4, 6, 7 and 8 also expressed varying degrees of activity. The structure-activity relationships (SARs) of these alkaloids were discussed.