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Six undescribed bisindole alkaloids, namely taberdisines A-F (1-6), were isolated from the leaves of Tabernaemontana divaricata 'Dwaft'. Among them, alkaloids 1 and 2 were the first examples of strychnos-iboga type alkaloid with both C-C linkage patterns. Alkaloid 3, a new type of aspidosperma-iboga with a furan-ring, as well as other three undescribed ones was disclosed. Their structures were elucidated by comprehensive spectroscopic analyses. Alkaloids 1 and 5 showed insecticide activity on Sf9 cell and eggs of Spodoptera frugiperda in vivo, which might explain the potential of the plants for insect resistance., 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 © 2024 Elsevier Ltd. All rights reserved.)

Phytochemical investigation of the two Tabernaemontana species (Apocynaceae) T . peduncularis Wall. and T . divaricata (L.) R.Br. ex Roem. & Schult. indicated closely related biosynthetic pathways leading to lipophilic and hydrophilic alkaloids. In total, 18 specialized metabolites comprising indole-derived alkaloid aglycones, three oxindole-derived alkaloid glycosides, and two iridoid glucosides could be identified in the studied species. Among the alkaloids, the two Iboga -type alkaloids 3,7-coronaridine isoindolenine, coronaridine 3,4-iminium and a javaniside derivative bearing a glucuronic acid, named javanuronic acid, could be described by spectroscopic and spectrometric methods for the first time. A docking experiment using alpha-fold was performed to generate a protein model of the enzyme 7-deoxyloganetic acid glucosyl transferase. Performed bioassays exhibited a growth reduction of neonate Spodoptera littoralis larvae and reduced cell viability of HepG2 cells of the extracts containing Iboga alkaloids, whilst the javaniside derivatives containing hydrophilic fraction did not show any effects. These findings indicate a high flexibility in the formation of bioactive indole alkaloid aglycones by Tabernaemontana species and also evidence similar accumulation trends in both species as well as indicate that biosynthetic routes leading to oxindole alkaloids like javanisides are more widespread than reported. Furthermore, the incorporation of the three novel compounds into potential biosynthetic pathways is discussed.

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., 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 B.V. All rights reserved.)

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 IC 50 values of 0.30, 0.75 and 3.41 μM, respectively (IC 50  = 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., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Thirty-one Vincan- and two Eburnan-type alkaloids were isolated from the aerial parts of Tabernaemontana bovina, whereas 20 of them are described the first time. Within the purified alkaloids, the firstly described taberbovcamine A features a 6/5/6/6/5 ring system. All the chemical structures were elucidated by employing extensive spectroscopic, computational electronic circular dichroism and X-ray diffraction methods. The two Eburnan-type alkaloids, 10,11-dimethoxy-16-O-methyllisoeburnamenine and 10,11-dimethoxy-isoeburnamenine were simultaneously identified by using the mentioned spectroscopic methods. Within the identified alkaloids, 10-hydroxy-14,15-didehydrovincanmine, 14,15-didehydrovincanmine, 14,15-didehydroapovincanmine, and criocerine increased the glucose consumption in a L6 myotube model., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Continued interest in bioactive alkaloids led to the isolation of four undescribed alkaloids along with 74 known ones from the aerial parts of Tabernaemontana bufalina Lour. The structures of the yet undescribed alkaloids were elucidated based on NMR, IR, UV, MS and CD spectroscopic data and X-ray crystal diffraction and, according to the plant source, named as taberhaines A-D (1-4). The known compounds comprised of 66 monoterpenoid indole, three carboline and five isoquinoline alkaloids. Among them, the known apparicine inhibited significantly the activity of xanthine oxidase, which plays an important role for gout, with an IC 50 value of 0.65 μM, compared to the standard drug allopurinol (IC 50  = 0.60 μM)., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Three monoterpenoid indole alkaloids (MIAs), tabernabovines A-C ( 1 - 3 ), were isolated from Tabernaemontana bovina. They were elucidated by spectroscopic data and computational calculations. Unlike precursors of MIAs, strictosidine and alstrostine A, alkaloid 1 consists of tryptamine and secologanin in a 2:1 ratio. Alkaloid 2 is a cage compound, and 3 possesses a bridged ring. Tabernabovine A exhibited inhibitory activity against NO production with IC 50 44.1 μM compared to l-NMMA with IC 50 of 48.6 μM.

Four unprecedented yellow alkaloids named as taberbovines A-D (1-4) were isolated from stems of Tabernaemontana bovina Lour. Their structures were elucidated by the comprehensive spectroscopic data, computational chemistry, and X-ray crystal diffraction. Alkaloids 1-4 possessed a unique 6/6/5/6/5 ring system and were assigned to monoterpenoid quinolines. Biosynthetically, the isolated alkaloids may be derived from Aspidosperma-type alkaloid by oxidation and rearrangements. Taberbovines A-D exhibited the good inhibitory activities of formation NO in LPS induced RAW264.7 macrophages.

Continued study in bioactive monoterpenoid alkaloids led to the isolation of nine undescribed alkaloids, taberyunines A-I, together with 32 known ones from the aerial parts of Tabernaemontana corymbosa Roxb. ex Wall (Apocynaceae). Among the undescribed alkaloids, taberyunines A-G and H-I were assigned to Aspidosperma-Aspidosperma and Vobasinyl-Ibogan type bisindoles, respectively. Their structures were determined by NMR spectra, MS data and X-ray diffraction. Taberyunine B showed significant cytotoxicity against three cancer cell lines., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Continued interest in cytotoxic alkaloids resulted in the isolation of 37 alkaloids including 29 known monoterpenoid indole alkaloids from the aerial parts of Tabernaemontana officinalis. Of the remaining 8 alkaloids, six were bisindole alkaloids named taberdivarines A-F (1-6) and the two were monomers named taberdivarines G and H (7-8). Alkaloids 1 and 2 are voaphylline-vobasinyl type bisindole alkaloids, a structural type previously unknown, while 3-6 exhibited cytotoxicity against three human cancer cell lines HeLa, MCF-7, and SW480 with IC50 values ranging from 1.42 to 11.35 μM., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Five new vobasinyl-ibogan-type bisindole alkaloids, tabernaricatines A-E (1-5), two new monomers, tabernaricatines F and G (6 and 7), and 24 known indole alkaloids were isolated from the aerial parts of Tabernaemontana divaricata. Alkaloids 1 and 2 are the first vobasinyl-ibogan-type alkaloids possessing a six-membered ring via an ether linkage between C-17 and C-21. All compounds except for 3 were evaluated for their cytotoxicity against five human cancer cell lines; conophylline showed significant bioactivity against HL-60, SMMC-7721, A-549, MCF-7, and SW480 cells with IC₅₀ values of 0.17, 0.35, 0.21, 1.02, and 1.49 μM, respectively.

Main observation and conclusion: Phytochemical investigations on Tabernaemontana divaricata led to the isolation of seven undescribed monoterpenoid indole alkaloids, taberdicatines A—G (1—7). Taberdicatines A—C might be derived from Aspidosperma‐type alkaloid, less skeletal carbons in 1—2 and an additional carbon in 3. Taberdicatines D—E (4—5) were attributed to Iboga alkaloids with enantiomeric skeleton, respectively. Alkaloid 3 could promote the neurite growth of mouse primary cortical neurons at the concentration of 5 μmol/L. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Two new pairs of monoterpenoid indole alkaloids (MIAs) enantiomers as well as their new congeners were isolated from stems of Tabernaemontana bovina Lour. (Apocynaceae). Their structures were elucidated by spectroscopic analyses and confirmed by X‐ray diffractions and computational calculations. Tabovine A, tabovine B and tabovines C—D possessed unprecedented 6/5/5/6/6, 6/5/5/6/5 and 6/5/6/6/6 ring systems, respectively. It is the first time to report co‐occurring enantiomers of MIAs. Additionally, the explanation concerning biogenesis of MIAs was provided. The findings would open a new window where we could disclose more diverse MIAs. [ABSTRACT FROM AUTHOR]

Abstract: Three new monoterpene indole alkaloids, 3α-hydroxymethyl-ibogamine (1), 3α-acetatemethoxyl-ibogamine (2), 16α-hydroxyl-ibogamine (3) together with six known alkaloids were isolated from the branches and leaves of Tabernaemontana divaricata (Apocynaceae). The structures of these alkaloids were determined by spectroscopic analyses. All isolated compounds showed no significant cytotoxicity against SGC-7901 gastric cancer, HeLa, and A-549 lung cancer cell lines (IC50 > 20 µM).Graphical Abstract: [ABSTRACT FROM AUTHOR]

Eleven undescribed tacamine type alkaloids, named tabercamines A–K were isolated from leaves of Tabernaemontana bovina , together with six known alkaloids. The planar structure of the undescribed alkaloids were determined by comprehensive spectroscopic data analysis. Their absolute configuration were established based on the combination of the electronic circular dichroism and single X-ray crystal diffraction analysis. The NMR rules (in acetone- d 6) of identifying of the stereo-configuration at C-20/16 was established. Image 1 • Eleven undescribed tacamine type alkaloids were isolated from leaves of Tabernaemontana bovina. • The absolute configuration of undescribed alkaloids were determined by NMR, single X-ray diffraction analysis and TDDFT-ECD data. • The rule of 13C NMR data was summarized, which was helpful to identify the stereo-configuration of C-16/20 in tacamines. [ABSTRACT FROM AUTHOR]