Ervahainine A, a new cyano-substituted oxindole alkaloid from Ervatamia hainanensis

Spirooxindol alkaloids from Voacanga africana: Targeting biofilm of MBLs producing Escherichia coli

Seven rarely spirooxindole alkaloids, voagafricines A-G (1-7) were isolated from the stem barks of Voacanga africana. Their structures were unambiguously elucidated by comprehensive spectroscopic data and electronic circular dichroism (ECD) analyses. 1 and 2 possess a unique indoleone system in conjugation with a 3,4'-decahydroquinoline spiral ring originating from seco-quinolhiddin core of the precursor, furthermore 1 undergo decarburization formed a novel C-3-nor monoterpenoid indole. All isolates were evaluated for their antibacterial activities against MBLs producing Escherichia coli strains. Compounds 1 and 7 were found to be potent inhibitors against E. coli 298 and 140 by targeting biofilm. Possible interaction sites of 1 and 7 with biofilm were preliminarily explored by means of molecular docking.

Stereoselective synthesis of highly substituted 1-isomorphans (1-azabicyclo[3.3.1]nonanes)

We describe the first enantioselective synthesis of highly functionalized 1-azabicyclo[3.3.1]nonanes (1-IM). The 1-IM scaffold is present in natural products and drugs and is an isomer of the morphan moiety. The proposed methodology is based on an organocatalytic Michael addition of N-protected piperidine ketoesters to nitroalkenes and an intramolecular nitro-Mannich reaction as key transformations. The 1-IMs feature 6 contiguous stereocenters, substituents at positions 2 and 4, and nitro, ester, and hydroxyl functional groups at positions 3, 5, and 6 respectively. The synthesis is straightforward, highly stereoselective (up to 98% ee, >99 : 1 d.r.), with overall yields of up to 83% and requires only two purification steps.

Chemical Diversity and Bioactivities of Monoterpene Indole Alkaloids (MIAs) from Six Apocynaceae Genera

By the end of the twentieth century, the interest in natural compounds as probable sources of drugs has declined and was replaced by other strategies such as molecular target-based drug discovery. However, in the recent times, natural compounds regained their position as extremely important source drug leads. Indole-containing compounds are under clinical use which includes vinblastine and vincristine (anticancer), atevirdine (anti-HIV), yohimbine (erectile dysfunction), reserpine (antihypertension), ajmalicine (vascular disorders), ajmaline (anti-arrhythmic), vincamine (vasodilator), etc. Monoterpene Indole Alkaloids (MIAs) deserve the curiosity and attention of researchers due to their chemical diversity and biological activities. These compounds were considered as an impending source of drug-lead. In this review 444 compounds, were identified from six genera belonging to the family Apocynaceae, will be discussed. These genera (Alstonia, Rauvolfia, Kopsia, Ervatamia, and Tabernaemontana, and Rhazya) consist of 400 members and represent 20% of Apocynaceae species. Only 30 (7.5%) species were investigated, whereas the rest are promising to be investigated. Eleven bioactivities, including antibacterial, antifungal, anti-inflammatory and immunosuppressant activities, were reported. Whereas cytotoxic effect represents 47% of the reported activities. Convincingly, the genera selected in this review are a wealthy source for future anticancer drug lead.

Three New Monoterpenoid Indole Alkaloids from Ervatamia pandacaqui

Three new monoterpenoid indole alkaloids, ervapandine A (1), (3R)-hydroxyibogaine (3), 12-hydroxyakuammicine N(4)-oxide (6), along with four known ones, were isolated from the twigs and leaves of Ervatamia pandacaqui. The structures of the new alkaloids were elucidated by spectroscopic methods and sugar hydrolysis experiment. All of the compounds were evaluated for their cytotoxicity against three human cell lines. Compound 7 showed moderate cytotoxic activity.

Ervadivamines A and B, Two Unusual Trimeric Monoterpenoid Indole Alkaloids from Ervatamia divaricata

Ervadivamines A (1) and B (2), two unprecedented trimeric monoterpenoid indole alkaloids, were isolated from Ervatamia divaricata. They are the first examples of vobasine-iboga-vobasine-type alkaloid with both C-C and C-N linkage patterns. Their structures including absolute configurations were fully accomplished by extensive spectroscopic analysis, single-crystal X-ray diffraction, and electric circular dichroism methods. The plausible biogenetic pathways of these trimeric alkaloids were also proposed. In addition, compound 1 exhibited significant cytotoxicity against four cancer cells.

Monoterpene indole alkaloids from Rhazya stricta

Twenty-seven monoterpene indole alkaloids (MIAs) including three new ones were isolated from the plant of Rhazya stricta. Their structures were elucidated by analyses of HRMS and NMR data. Secopleiocarpamine A (1) represents a novel 2,3-seco pleiocarpamine type MIA possessing a cyano group. A possible biosynthetic pathway for 1 was postulated. All compounds were evaluated for their inhibitory activities against six Candida strains, and the results showed that 2, 5, 12, 21, 23, and 27 exhibited moderate inhibitory activities with MIC values ranging from 3.125 to 50 μg/mL.

Ervaoffines E–G, three iboga-type alkaloids featuring ring C cleavage and rearrangement from Ervatamia officinalis

Three novel alkaloids (1–3) reveal the high structural plasticity of ring C in iboga-type alkaloids.

Aspidosperma-type Alkaloids from Melodinus Suaveolens

Three new aspidosperma-type alkaloids, 3-oxo-11-hydroxytabersonine (2), 11-hydroxytabersonine N-oxide (3) and 11-methoxytabersonine N-oxide (4), along with three known ones were isolated from the twigs and leaves of Melodinus suaveolens. The structures of the new compounds were elucidated by using spectroscopic methods, and circular dichroism experiments. The known compounds were identified by comparing their spectroscopic data with those reported in the literature.

Winchinines A and B, two unusual monoterpene indole alkaloids with a third nitrogen atom from Winchia calophylla

Two novel monoterpenoid indole alkaloids with a third nitrogen atom were isolated from the twigs and leaves of Winchia calophylla.

New iboga-type alkaloids from Ervatamia hainanensis

The structures and absolute configurations of seven new iboga-type alkaloids 1–7 were determined by spectroscopic data, Mosher's method, single crystal X-ray diffraction and ECD analyses.

Two New Oxindole Alkaloid Glycosides from the Leaves of Nauclea officinalis

Two new oxindole alkaloid glycosides, nauclealomide A and (3 S,7 R)-javaniside, were isolated from the leaves of Nauclea officinalis. Their structures and absolute configurations were elucidated by means of NMR, HRESIMS, X-ray diffraction, acid hydrolysis and quantum chemical CD calculation. Nauclealomide A is a novel monoterpenoid oxindole alkaloid possessing a rare tetrahydro-2 H–1,3-oxazine ring.

Ervatamines A-I, Anti-inflammatory Monoterpenoid Indole Alkaloids with Diverse Skeletons from Ervatamia hainanensis

Nine new monoterpenoid indole alkaloids, ervatamines A-I (1-9), and five known ones (10-14), were isolated from Ervatamia hainanensis. The new structures were elucidated by extensive spectroscopic analysis and comparison to known compounds. Their absolute configurations were determined by various methods including computational methods, X-ray diffraction analysis, and electronic circular dichroism spectroscopy, as well as chemical transformations. Ervatamine A (1) is a ring-C-contracted ibogan-type monoterpenoid indole alkaloid with an unusual 6/5/6/6/6 pentacyclic rearranged ring system. Ervatamines B-E (2-5) display a nitrogen-containing 9/6 ring system, which is rarely observed in nature. The epimeric ervatamines B (2) and C (3) possess a 22-nor-monoterpenoid indole alkaloid carbon skeleton, which was only found in deformylstemmadenine. Compounds 10 and 14 exhibited significant anti-inflammatory activities, with IC50 values of 25.5 and 41.5 μM, respectively, while the IC50 value of indomethacin as a positive control was found to be 42.6 μM. Additionally, compound 9 showed mild activity against 786-O and HL-60 cell lines.

Simple indole alkaloids and those with a nonrearranged monoterpenoid unit

This review summarizes the isolation, structure determination, total syntheses and biological activities of simple indole alkaloids and those with a nonrearranged monoterpenoid unit, with literature coverage from 2012 to 2013.

Iboga-Type Alkaloids from Ervatamia officinalis

Seven new iboga-type alkaloids, ervaoffines A-D (1-4), (7S)-3-oxoibogaine hydroxyindolenine (5), ibogaine-5,6-dione (6), and 19-epi-5-oxovoacristine (7), and 10 known alkaloids were isolated from Ervatamia officinalis. The absolute configurations of 1-7 were determined through X-ray diffraction and electronic circular dichroism (ECD) analyses. Ervaoffines A and B represent the first iboga-type pseudoindoxyl alkaloids in which the C-2 spiro carbon configuration is opposite to that of other members of this class, such as iboluteine (8). The relationship between the absolute configuration of the spiro carbons and the Cotton effect in the ECD spectrum is established for the first time for iboga-type pseudoindoxyl and oxindole alkaloids. Additionally, a plausible biogenetic pathway for these alkaloids is proposed.