Montamine, a unique dimeric indole alkaloid, from the seeds of Centaurea montana (Asteraceae), and its in vitro cytotoxic activity against the CaCo2 colon cancer cells

Reversed-phase HPLC analysis of the methanol extract of the seeds of Centaurea montana afforded a flavanone, montanoside (4), six epoxylignans, berchemol (7), berchemol 4′-O-β-d-glucoside (5), pinoresinol (10), pinoresinol 4-O-β-d-glucoside (8), pinoresinol 4,4′-di-O-β-d-glucoside (6), pinoresinol 4-O-apiose-(1→2)-β-d-glucoside (9), two quinic acid derivatives, trans-3-O-p-coumaroylquinic acid (1), cis-3-O-p-coumaroylquinic acid (2), and eight indole alkaloids, tryptamine (3), N-(4-hydroxycinnamoyl)-5-hydroxytryptamine (11), cis-N-(4-hydroxycinnamoyl)-5-hydroxytryptamine (12), centcyamine (16), cis-centcyamine (17), moschamine (13), cis-moschamine (14) and a dimeric indole alkaloid, montamine (15). While the structures of two new compounds, montanoside (4) and montamine (15), were established unequivocally by UV, IR, MS and a series of 1D and 2D NMR analyses, all known compounds were identified by comparison of their spectroscopic data with literature data. The antioxidant properties of these compounds were assessed by the DPPH assay, and their toxicity towards brine shrimps and cytotoxicity against CaCo-2 colon cancer cells were evaluated by the brine shrimp lethality and the MTT cytotoxicity assays, respectively. The novel dimer, montamine (15), showed significant in vitro anticolon cancer activity (IC₅₀=43.9 μM) while that of the monomer, moschamine (13), was of a moderate level (IC₅₀=81.0 μM).     

Isolation, structure elucidation and biological activity of hederacine A and B, two unique alkaloids from Glechoma hederaceae

Preparative HPLC purification of a methanol extract of the aerial parts of Glechoma hederaceae has yielded two unique alkaloids, hederacine A (1) and hederacine B (2). The structures of these compounds were established unequivocally by UV, IR, MS and a series of 1D and 2D NMR analyses. These alkaloids were inactive against any of the 11 bacterial species at test concentrations, but showed prominent toxicity in the brine shrimp lethality assay (LC₅₀s=3.2, 14.0 and 2.7 μg/mL, respectively, for 1, 2 and the positive control, podophyllotoxin).     

Isolation and structure elucidation of new sesquiterpenes of protoilludane origin from the fungus Clavicorona divaricata

Four novel sesquiterpenes of protoilludane origin, divaricatines A 3a and B 3b, 7-epitsugicoline H 4a and tsugicoline M 5a have been isolated from agar cultures of the fungus Clavicorona divaricata (Basidiomycetes). Their structures were elucidated by means of NMR studies and chemical correlations. All the metabolites are weakly active on bacteria but inhibited the germination of the water cress Lepidium sativum. A possible mechanism of their formation from the protoilludane tsugicoline A 1 is suggested. A fifth metabolite, the norsesquiterpene tsugicoline L 2b, was also isolated from the same fungus together with the known tsugicoline I 2a.     

Ikirydinium A: a new indole alkaloid from the seeds of Hunteria umbellata (K. Schum)

Chemical investigations into samples of Hunteria umbellata (K. Schum) collected in Osun State, Nigeria, led to the discovery of a new indole alkaloid, ikirydinium A, featuring an unprecedented 3-alkylpyridinium-indole-2-carboxylate scaffold. Ikirydinium A was found to exhibit antimicrobial activity (IC₅₀ 0.6 μM) against Bacillus subtilis ATCC 6051. The involvement of a common intermediate in the biosynthesis of ikirydinium A and vinblastine is hypothesized.     

Spectroscopic analyses and chemical transformation for structure elucidation of two novel indole alkaloids from Gelsemium elegans

Two new monoterpenoid oxindole alkaloids, gelsevanillidine (1) having an additional vanillin residue on gelsenicine-type alkaloid and gelseoxazolidinine (2) possessing an unusual oxazolidine ring, were isolated from Gelsemium elegans. To confirm their structures, the chemical transformation of a humantenine-type alkaloid into gelsevanillidine (1) and the deacetoxy derivative of gelseoxazolidinine was performed.     

An unusual indole alkaloid with anti-adenovirus and anti-HSV activities from Alstonia scholaris

A novel alkaloid, 17-nor-excelsinidine (1), possessing an unusual 1-azoniatricyclo [4.3.3.0] undecane moiety was isolated from the twigs and leaves of Alstonia scholaris alongside its biogenetically related strictamine (2). The structure and absolute stereochemistry of compound 1 were rigorously determined by a combination of NMR spectroscopy and X-ray crystallography. The 17-nor-excelsinidine (1) and strictamine (2) showed significant inhibitory activity against herpes simplex virus (HSV) and adenovirus (ADV).     

Synthetic approaches towards an indole alkaloid isolated from the marine sponge Halichondria melanodocia

The exocyclic analogue of the indole alkaloid isolated from the marine sponge Halichondria melanodocia has been prepared via olefination of a phosphonoester derived from 3-(2-bromoacyl)indole. The formation of an unexpected indolylazepine is also discussed.     

Kingamide A, a new indole alkaloid from the ascidian Leptoclinides kingi

Chemical investigation of the CH₂Cl₂/MeOH extract from the Australian ascidian Leptoclinideskingi led to the isolation of a new brominated indole alkaloid, kingamide A (1). The planar structure of kingamide A was elucidated following the interpretation of 1D/2D NMR and MS data, and the absolute configuration was determined using Marfey’s method. This is the first report of a natural product from L. kingi.     

Isolation and structure determination of pulicazine, a new sesquiterpene lactone from the Tunisian Pulicaria laciniata (Coss.et Kral.) Thell.

A new naturally occurring pseudo-guaianolide type sesquiterpene lactone named pulicazine along with ent-11β,15β-dihydroxykaur-16-en-19-oic acid is isolated from the Tunisian Pulicaria laciniata (Coss.et Kral.) Thell. flowers. Their structures were elucidated by NMR spectroscopy and their stereochemistries were established by X-ray diffraction.     

A pair of unique sesquiterpene-chalcone conjugates isolated from the seeds of Alpinia katsumadai

Sumadains A (1) and B (2), a pair of unique isomeric sesquiterpene-chalcone conjugates with unprecedented skeletons, were isolated from the seeds of Alpinia katsumadai. Their structures and relative configurations were established by NMR spectroscopy and X-ray crystallography.     

Hericirine,a novel anti-inflammatory alkaloid from Hericium erinaceum

A novel ergosterol conjunction-type alkaloid, hericirine (1), was isolated from the dried fruiting bodies of Hericium erinaceum. The overall framework of 1 was isolated, and combined with hericerin and ergosterol. Its structure was elucidated based on spectroscopic analysis using 1D and 2D NMR, IR and HRESIMS techniques. We found that hericirine significantly inhibited protein expression of iNOS and COX-2 and reduced NO, PGE₂, TNF-α, IL-6 and IL-1β production in RAW264.7 cells exposed to LPS.     

Andrographolactone, a unique diterpene from Andrographis paniculata

Andrographolactone (1), possessing an unprecedented diterpene skeleton, was isolated from the EtOAc extract of the aerial parts of Andrographis paniculata. Its structure was established by NMR, IR, UV, and HRESIMS data and subsequently confirmed by X-ray diffraction analysis. A possible biogenetic pathway of 1 was also proposed. Bioassay showed that 1 exhibited cytotoxic activity.     

Isolation,characterization, and NMR spectroscopic data of indole and oxindole alkaloids from Mitragyna speciosa

A new indole alkaloid, 7β-hydroxy-7H-mitraciliatine (1) and a new oxindole alkaloid, isospeciofoleine (2) together with nine known alkaloids were isolated from Mitragyna speciosa and characterized by NMR, CD, and MS spectroscopic data analyses. The ¹H and ¹³C NMR spectroscopic data of isospeciofoline (3), isorotundifoline (4), paynantheine (5), and 3-isopaynantheine (6) were also reported for the first time.     

Lycopladine H, a novel alkaloid with fused-tetracyclic skeleton from Lycopodium complanatum

A novel Lycopodium alkaloid, lycopladine H (1), with a fused-tetracyclic ring system consisting of an azocane ring connected to a [2,2,2]-bicyclooctane ring and a 3-piperidone ring, was isolated from the club moss Lycopodium complanatum. The structure and relative stereochemistry of 1 were elucidated on the basis of spectroscopic data.     

Isolation and biological evaluation of chromone alkaloid dysoline,a new regioisomer of rohitukine from Dysoxylum binectariferum

The chromone alkaloid dysoline (1), a new regioisomer of rohitukine (2) along with rohitukine and rohitukine-N-oxide (3) were isolated from the stem barks of Dysoxylum binectariferum. The structure of dysoline (1) was determined by extensive 2D-NMR studies and the absolute configuration was established by NOESY and CD spectra. Dysoline (1) consisted of a 5,7-dihydroxy-2-methylchromone nucleus substituted with a 2′-hydroxylated N-Me piperidine ring at the C-6 position. Dysoline differs from rohitukine by the position of the piperidine ring on the chromone nucleus. Dysoline displayed promising cytotoxicity in HT1080 fibrosarcoma cells with an IC₅₀ of 0.21 μM, and also displayed significant inhibition of proinflammatory cytokines TNF-α and IL-6.     

Naupliolide, a sesquiterpene lactone with a novel tetracyclic skeleton from Nauplius graveolens subsp. odorus

The aerial parts of Nauplius graveolens subsp. odorus (Schousb) Wikl. afforded a novel sesquiterpene lactone (1) named naupliolide together with the known 6,7,9,10-tetradehydroasteriscanolide 2 and asteriscunolides A-D 3a-d. The structure of compound 1 corresponds to a novel skeleton of 14,15-dimethyl-7,13-dioxotricyclic[6.4.0.0^9,11]dodeca-12,13-olide, and was established on the basis of spectroscopic methods including 2D-NMR. The coexistence of naupliolide 1 together with the structurally related sesquiterpene lactones asterisculolides A-D (3a-d) and 6,7,9,10-tetradehydroasteriscanolide 2, seems to indicate their biosynthetic relationship.     

N-Demethyl-sauroxine,a novel Lycodine Group alkaloid from Huperzia saururus

The present study describes the isolation and identification of N-demethyl-sauroxine, a novel Lycopodium alkaloid obtained from Huperzia saururus (Lam.) Trevis. (Lycopodiaceae). Its structure and relative stereochemistry were elucidated on the basis of its spectral data and chemical correlations. Additionally, acetylcholinesterase inhibitory activity was evaluated (IC₅₀ = 209.6 ± 1.1 μM). The structure of the already identified alkaloid sauroxine was also re-validated through two dimensional NMR data.     

Spironaamidine, a new spiroquinone-containing alkaloid from the marine sponge Leucetta microraphis

Spironaamidine (1), a unique spiroquinone-containing alkaloid, was isolated from the marine sponge, Leucetta microraphis, along with two known imidazole alkaloids, naamidine H (2) and (9E)-clathridine 9-N-(2-sulfoethyl)imine (3). Spironaamidine (1) showed antimicrobial activity against Bacillus cereus.     

Two novel indole alkaloids, Kopsiyunnanines A and B, from a Yunnan Kopsia

Two novel indole alkaloids having unusual skeletons were isolated from the aerial part of Yunnan Kopsia arborea. Kopsiyunnanine A (1) is a new class of bisindole alkaloid composed of vallesiachotamine (modified Corynanthe-type) and Aspidospermatan-type alkaloids. Kopsiyunnanine B (2) is a new Corynanthe-type oxindole alkaloid rearranged by D ring rotation.     

Calyciphylline G, a novel alkaloid with an unprecedented fused-hexacyclic skeleton from Daphniphyllum calycinum

Calyciphylline G (1), a novel Daphniphyllum alkaloid with an unprecedented fused-hexacyclic skeleton containing a 5-azatricyclo[6.2.1.0^1,5]undecane ring, has been isolated from the stem of Daphniphyllum calycinum (Daphniphyllaceae), and the structure and relative stereochemistry were elucidated on the basis of spectroscopic data.