Two New Indole Alkaloids from the Bark of Anthocephalus chinensis

Two new indole alkaloids, cadambinic acid ( 1 ) and isonauclefidine ( 2 ), were isolated from the bark of Anthocephalus chinensis. The structures were identified by spectroscopic methods, and the compounds were tested for their biological activities. Both compounds showed weak cytotoxicities against A549, BGC‐823, and HeLa cells in biological assays.     

Three New Indole Alkaloids from the Leaves of Kopsia officinalis

Three new indole alkaloids, 11,12‐de(methylenedioxy)danuphylline ( 1 ), methyl (2β,11β,12β,19α)‐6,7‐didehydro‐8,21‐dioxo‐11,21‐cycloaspidospermidine‐2‐carboxylate ( 2 ), and (2β,5β)‐aspidofractinin‐16‐ol ( 3 ) were isolated from Kopsia officinalis, together with 16 known compounds. Their structures were determined by spectroscopic methods. The isolated known compound (?)‐12‐methoxykopsinaline displayed antimanic effects in Drosophila, with an IC₅₀ value of 12.5 μg/ml.     

Two New Indole Alkaloids from Emmenopterys henryi

Two new indole alkaloids, 5‐oxodolichantoside ( 1 ) and deglycocadambine ( 2 ), were isolated from the twigs and leaves of Emmenopterys henryi, together with four known indole alkaloids and five known iridoids. The structures of the new compounds were elucidated on the basis of extensive spectroscopic analyses, including 1D‐ and 2D‐NMR experiments, and confirmed by single‐crystal X‐ray diffraction studies. This is the first report on the isolation of indole alkaloids from this species. The indole alkaloids were evaluated for their cytotoxic activities against five human cancer lines.     

Flabelliformides A and B,Two Novel Indole Alkaloids from Ervatamia flabelliformis

Flabelliformides A ( 1 ) and B ( 2 ), containing a novel C₂₀ indole core, have been isolated from the stems of Ervatamia flabelliformis. The structures of 1 and 2 were elucidated on the basis of spectral analysis and X‐ray crystallography.     

New Indole Alkaloids from Rauvolfia yunnanensis

Three new indole alkaloids, 10‐methoxy‐16‐de(methoxycarbonyl)pagicerine ( 1 ), (5β)‐17‐O‐deacetyl‐5,11‐dimethoxyakuammiline ( 2 ), and ((16S,19E)‐N¹‐(hydroxymethyl)isositsirikine ( 3 ) were isolated from the roots of Rauvolfia yunnanensis, together with seven known alkaloids. The structures of the new compounds were elucidated by in‐depth spectroscopic and mass‐spectrometric analyses.     

Two New Indole Alkaloids from Tabernaemontana hystrix Steud. (Apocynaceae)

Two new monoterpene indole alkaloids named ibogamine‐7,8‐dione ( 1 ) and 12‐methoxyvoachalotine ( 2 ), and eight known ones, coronaridine ( 3 ), coronaridine hydroxyindolenine ( 4 ), 5‐oxocoronaridine ( 5 ), 3‐oxocoronaridine hydroxyindolenine ( 6 ), 3‐oxocoronaridine ( 7 ), vobasine ( 8 ), ibogamine ( 9 ), and olivacine ( 10 ), were isolated from a CH₂Cl₂ extract of the root bark from Tabernaemontana hystrix. The structures of the compounds were elucidated on the basis of spectroscopic data analyses, mainly ¹H‐ and ¹³C‐NMR, including 2D experiments (¹H,¹H‐COSY, HMBC, and HMQC).     

Structure and Dynamic of Three Indole Alkaloids from the Campylospermum Genus (Ochnaceae)

A new indole alkaloid, calanthumindole ( 4 ), and three known biflavonoids, amentoflavone, sequoiaflavone, and podoscarpusflavone B, were isolated from Campylospermum calanthum (Ochnaceae). Calanthumindole is a new indole alkaloid of the serotobenine family characterized by the presence of a C?C bond between atoms C(7′) and C(8′) of the furan ring. This is the first compound to have a fully unsaturated furan ring among the members of this family. The combination of NMR and DFT allowed the determination and comparison of the 3D structures and relevant conformational characteristics of serotobenine ( 1 ), flavumindole ( 2 ), and calanthumindole ( 4 ).     

Two Novel Plumeran Indole Alkaloids Isolated from Aspidosperma cylindrocarpon (Apocynaceae)

Two novel indole alkaloids with plumeran skeleton, N‐benzoyl‐12‐demethoxycylindrocarine and N‐cinnamoyl‐12‐demethoxycylindrocarine ( 1 and 2 , resp.), were isolated from the MeOH extract of the stem bark of Aspidosperma cylindrocarpon Müll .Arg . These compounds were obtained by high‐speed counter‐current chromatography, and their structures were elucidated on the basis of their NMR (1D and 2D) data. They were tested in vitro against chloroquine‐resistant strains of Plasmodium falciparum, and only 2 showed a weak activity (IC₅₀ 127.97 ng/ml with respect to the standard drug). Several other known compounds, comprising steroids, flavonoids, the rarely found atraric acid, as well as the previously reported alkaloid 3 , were also isolated by conventional chromatographic techniques.     

A New Indole Alkaloid from Cleome droserifolia

The phytochemical investigations on Cleome droserifolia resulted in the isolation and characterization of a new indole alkaloid, 5‐hydroxy‐2‐methoxy‐1‐methyl‐1H‐indole‐3‐carbaldehyde ( 1 ). The structure elucidation was carried out on the basis of 1D‐ and 2D‐NMR techniques. In addition to 1 , two known aromatic derivatives, veratrol ( 2 ) and 2‐methoxy‐4‐methylacetophenone ( 3 ), were also obtained. All these compounds were purified by repeated column chromatography of the CH₂Cl₂ fraction obtained from MeOH extract of Cleome droserifolia. The structure of the new compound 1 was finally confirmed by the combined 1D (¹H‐ and ¹³C‐) and 2D (H? C correlations; HMBC and HSQC) NMR and IR spectroscopy, mass spectrometry (MS), and UV absorption spectroscopy techniques. The comparison of the physical and spectroscopic data with those in the literature provided evidence for the structure confirmation of known compounds. All the purified compounds were subjected to urease and α‐glucosidase enzymes inhibition. The results showed that compound 1 was more potent with an IC₅₀ value 11.97±2.067 μg/ml towards urease inhibition, while the activity of α‐glucosidase enzyme was marginal.     

Two New 11‐Hydroxy‐Substituted Gelsedine‐Type Indole Alkaloids from the Stems of Gelsemium elegans

Two new 11‐hydroxy‐substituted gelsedine‐type indole alkaloids, named 11,14‐dihydroxygelsenicine ( 1 ) and 11‐hydroxygelsenicine ( 2 ), together with six known alkaloids, i.e., koumine, gelsemine, 14‐hydroxygelsenicine, 11‐hydroxyhumantenine, gelsenicine, and (19Z)‐akuammidine, were isolated from the EtOH extract of the stems of Gelsemium elegans Benth. Their structures were determined mainly by means of spectroscopic analyses including HR‐ESI‐MS and 2D‐NMR (HSQC, HMBC, ¹H,¹H‐COSY). The configuration of 1 was confirmed by X‐ray‐diffraction analysis.     

Three New Monoterpenoid Indole Alkaloids from Ervatamia flabelliformis

The three new monoterpenoid indole alkaloids 1 – 3 were isolated from the stems of Ervatamia flabelliformis. The structures were elucidated on the basis of spectral analysis and chemical derivatization.     

Two Novel Alkaloids from Zanthoxylum nitidum

Two novel alkaloids, 4,5‐dihydroxy‐1‐methyl‐3‐oxo‐2‐(trichloromethyl)‐3H‐indolium chloride ( 1 ) and 4‐(2‐methoxyethyl)‐N,N‐dimethylbenzenamine ( 2 ), were isolated from the EtOH extract of the roots of Zanthoxylum nitidum. Their structures were identified on the basis of spectroscopic and mass‐spectrometric analyses.     

Two New Indole Alkaloids from the Marine‐Derived Bacterium Aeromonas sp. CB101

Two new indole alkaloids, arsindolines A and B ( 1 and 2 , resp.), together with six known indole alkaloids, were isolated from a marine‐derived bacterium strain CB101, identified as Aeromonas sp. Their structures were established by spectroscopic methods, and their antitumor activities were evaluated by SRB and MTT methods.     

Alkaloids from Ochrosia borbonica

Ten new monoterpenoid indole alkaloids, ochroborines A and B ( 1 and 2 , resp.), 10‐hydroxyisovallesiachotamine ( 3 ), 10‐hydroxyisositsirikine ( 4 ), 10,11‐dimethoxysitsirikine ( 5 ), 10‐methoxyapoyohimbine ( 6 ), 10‐hydroxyakuammidine ( 7 ), akuammidine 17‐O‐β‐D ‐glucoside ( 8 ), 15α‐hydroxyapparicine ( 9 ), and 15α‐hydroxy‐10‐methoxyapparicine ( 10 ), and 24 known alkaloids were isolated from leaves and twigs of Ochrosia borbonica J. F.Gmel . These structures were elucidated based on 1D‐ and 2D‐NMR, FT‐IR, UV, and MS data. 10‐Hydroxyisovallesiachotamine ( 3 ), ellipticine, and 10‐methoxyellipticine showed cytotoxic activities against five human cancer cell lines.     

Monoterpenoid Indole Alkaloids from Alstonia mairei

Three new monoterpenoid indole alkaloids, (14α,15α)‐14,15‐epoxyaspidofractinine ( 1 ) and maireines A and B ( 2 and 3 , resp.), together with 19 known alkaloids, were isolated from the leaves and twigs of Alstonia mairei. The structures of the new compounds were elucidated by 1D‐ and 2D‐NMR spectroscopic methods in combination with MS experiments.     

New Indole Alkaloids from Kopsia. Alkaloid Variation in Kopsia singapurensis

Five new indole alkaloids, viz., kopsiloscine G ( 2 ), kopsidarine ( 4 ), kopsimaline F ( 6 ), kopsidine C N‐oxide ( 7 ), and aspidophylline B ( 9 ), in addition to 17 other known alkaloids, were obtained from the leaf and stem‐bark extract of the Malaysian Kopsia singapurensis. The structures were determined by using NMR and MS analysis. The results are compared with the alkaloidal composition of another sample of K. singapurensis, collected from the same location but at a different time of the year, as well as with other samples of K. singapurensis collected from different locations.     

Flavonoid Aglycones and Indole Alkaloids from the Roots of Acacia Confusa

From the methanolic extract of the roots of Acacia confusa Merr. (Leguminosae), (‐)‐2,3‐cis‐3,4‐cis‐4′‐methoxy‐3,3′,4,7,8‐pentahydroxyflavan ( 1 ), (‐)‐2,3‐cis‐3,4‐cis‐3,3′,4,4′,7,8‐hexahydroxyflavan ( 2 ), (‐)‐2,3‐trans‐3′,4′,7,8‐tetrahydroxydihydroflavonol ( 3 ), (+)‐catechin ( 4 ), (‐)‐epicatechin ( 5 ), 3′,4′,7,8‐tetrahydroxyflavonol ( 6 ) together with N‐methyltryptamine ( 7 ) and N,N‐dimethyltryptamine ( 8 ) were isolated, and their structures were established by analysis of their spectroscopic data. Among them, compound 1 was a new flavonoid. Additionally, the results of chromatographic bioassay on lettuce seeds indicated that compounds 7 and 8 exhibited significant phytotoxicity at a concentration lower than 14 mM.     

Further Alkaloids from the Leaves of Trigonostemon lii

Four new indole alkaloids, trigonoliimines D–G ( 1 – 4 , resp.), were isolated from Trigonostemon lii. Their structures were elucidated by spectroscopic methods, including extensive 1D‐ and 2D‐NMR experiments.     

Kopsine and Danuphylline Alkaloids from Kopsia. Biomimetic Partial Synthesis of Danuphylline B

Two new indole alkaloids, 12‐methoxykopsine ( 6 ) and danuphylline B ( 7 ), were obtained from the leaf extract of the Malayan Kopsia species, K. arborea, and their structures established by spectroscopic analysis. An electrochemically‐mediated partial synthesis of the ring‐opened alkaloid, danuphylline B from the hexacyclic alkaloid, methyl N(1)‐de(methoxycarbonyl)chanofruticosinate was carried out.     

Alkaloids from stems of Ervatamia yunnanensis

Six indole alkaloids were isolated from the stems of Ervatamia yunnanensis. Among them, yunnanensine (I) is new. The other five are known alkaloids, namely: 19,20-E-vallesamine (II), 19s-heyneanine (HI), ibogaine (IV), ibogamine (V), coronaridine (VI). The structural elucidation of the alkaloids was based on spectral means.