Pegaharmols A-B, Axially Chiral ß-Carboline-quinazoline Dimers from the Roots of Peganum harmala.

Two nonbiaryl axially chiral ß-carboline-quinazoline dimers, pegaharmols A (1) and B (2), were isolated from the roots of Peganum harmala. Their planar structures were elucidated by the spectroscopic methods of high-resolution mass spectrometry and 1D and 2D nuclear magnetic resonance (NMR). The stereochemistry was established by a comparison between the experimental data of NMR and electronic circular dichroism and the computed data by quantum mechanical calculations. It is discovered for the first time that the ß-carboline at the C-8 position is bonded to the vasicine at the C-9 position. 1 exhibited moderate cytotoxic activity against HL-60 and A549 cell lines.

Tunicyclin L, a cyclic peptide from Psammosilene tunicoides: Isolation, characterization, conformational studies and biological activity.

Tunicyclin L (1), cyclo (L-Pro1-Gly-L-Phe1-L-Ile-L-Pro2-L-Phe2 -L-Thr-L-Val), and 11 known compounds, including one cyclic peptide (2), eight carboline alkaloids (3 -10), one lignan (11) and one flavone (12) were isolated from the roots of Psammosilene tunicoides. Their structures were elucidated on the basis of extensive UV, IR, MS, NMR spectroscopic data and comparison with literature. Single-crystal X-ray diffraction results revealed the stereochemistry of the 24-membered ring cyclic peptide (1). Among these known compounds, compound 6 was found to be a new natural product, and compounds 3, 4, and 11 were isolated from this plant for the first time. Five compounds (1, 3, 4, 7, and 9) showed moderate anti-acetylcholinesterase (AChE) activity.

1-Carbomethoxy-ß-Carboline, Derived from Portulaca oleracea L., Ameliorates LPS-Mediated Inflammatory Response Associated with MAPK Signaling and Nuclear Translocation of NF-κB.

Portulaca oleracea is as a medicinal plant known for its neuroprotective, hepatoprotective, antidiabetic, antioxidant, anticancer, antimicrobial, antiulcerogenic, and anti-inflammatory activities. However, the specific active compounds responsible for the individual pharmacological effects of P. oleracea extract (95% EtOH) remain unknown. Here, we hypothesized that alkaloids, the most abundant constituents in P. oleracea extract, are responsible for its anti-inflammatory activity. We investigated the phytochemical substituents (compounds 1-22) using nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS) and screened their effects on NO production in lipopolysaccharide (LPS)-induced macrophages. Compound 20, 1-carbomethoxy-ß-carboline, as an alkaloid structure, ameliorated nitric oxide (NO) production, inducible nitric oxide synthase (iNOS), and proinflammatory cytokines associated with the mitogen-activated protein kinase (MAPK) pathways, p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK). Subsequently, we observed that compound 20 suppressed nuclear translocation of nuclear factor κB (NF-κB) using immunocytochemistry. Moreover, we recently reported that compound 8, trans-N-feruloyl-3', 7'-dimethoxytyramine, was originally purified from P. oleracea extracts. Our results suggest that 1-carbomethoxy-ß-carboline, the most effective anti-inflammatory agent among alkaloids in the 95% EtOH extract of P. oleracea, was suppressing the MAPK pathway and nuclear translocation of NF-κB. Therefore, P. oleracea extracts and specifically 1-carbomethoxy-ß-carboline may be novel therapeutic candidates for the treatment of inflammatory diseases associated with the activation of MAPKs and NF-κB.

A new cinnamamide derivative and two new ß-carboline alkaloids from the stems of Picrasma quassioides.

Picrasamide A (1), a new cinnamamide derivative, together with two new ß-carboline alkaloids (2 and 3) and five known ß-carboline alkaloids (4-8) were isolated from the stems of Picrasma quassioides (D. Don) Benn. Their structures were elucidated by detailed analyses of UV, IR, HRESIMS, and NMR data. Compound 1 was the first case of cinnamamide derivative from genus Picrasma. The AChE inhibitory activity and the antimicrobial activity of 1-8 were assessed. In addition, preliminary structure-activity relationships of these ß-carboline alkaloids on the AChE inhibitory activity and antimicrobial activity were proposed.

Isolation and structural elucidation of a novel brunnein-type antioxidant ß-carboline alkaloid from Cyclocybe cylindracea.

Effect-directed isolation of free radical scavengers from the methanol extract of the freeze-dried fruiting bodies of the cultivated basidiomycetous mushroom, black poplar (Cyclocybe cylindracea), yielded a ß-carboline alkaloid. Its structure was determined based on ESI-TOF-MS/MS, NMR and circular dichroism spectra by comparison with published data. The compound, identified as the C1-S diastereomer of brunnein B, exhibited explicit radical scavenging activity (EC50 = 119.1 ±â€¯1.2 µg/mL). The quantity of the active component was determined with HPLC-MS in the fruiting body (36.2 ±â€¯2.8 ng/g DW, dry weight) and its different tissues such as peel (94.7 ±â€¯1.9 ng/g DW), inner cap (90.5 ±â€¯1.3 ng/g DW), gills (71.5 ±â€¯0.6 ng/g DW), and stipe (162.2 ±â€¯1.7 ng/g DW). It is a ß-carboline alkaloid that was not reported previously.

Effects of Enantiomerically Pure ß-Carboline Alkaloids from Picrasma quassioides on Human Hepatoma Cells.

Four pairs of ß-carboline enantiomers (1A: /1B: -4A: /4B: ), 2 ß-carboline derivatives (5:  - 6: ) with a single enantiomeric configuration, together with 2 known achiral congeners (7:  - 8: ) were isolated from the stems of Picrasma quassioides. Their structures were elucidated on the basis of extensive spectroscopic analyses and quantum mechanical calculations. Compound 5: possesses a 4,5-seco ß-carboline framework and represents the first example of this type of ß-carboline alkaloids from nature. A possible biosynthetic pathway is proposed to generate the racemate 4: and the enantiomerically pure compounds 5: and 6: . All isolates were screened for their cytotoxicity against hepatocellular carcinoma Hep3B and HepG2 cells, which revealed that enantiomeric compounds 4A: and 4B: had distinctive effects in HepG2 cells. Further investigation showed that 4B: could induce apoptosis in HepG2 cells.

Flavopereirine-An Alkaloid Derived from Geissospermum vellosii-Presents Leishmanicidal Activity In Vitro.

Chemotherapy is limited in the treatment of leishmaniasis due to the toxic effects of drugs, low efficacy of alternative treatments, and resistance of the parasite. This work assesses the in vitro activity of flavopereirine on promastigote cultures of Leishmania amazonensis. In addition, an in silico evaluation of the physicochemical characteristics of this alkaloid is performed. The extract and fractions were characterized by thin-layer chromatography and HPLC-DAD, yielding an alkaloid identified by NMR. The antileishmanial activity and cytotoxicity were assayed by cell viability test (MTT). The theoretical molecular properties were calculated on the Molinspiration website. The fractionation made it possible to isolate a beta-carboline alkaloid (flavopereirine) in the alkaloid fraction. Moreover, it led to obtaining a fraction with greater antileishmanial activity, since flavopereirine is very active. Regarding the exposure time, a greater inhibitory effect of flavopereirine was observed at 24 h and 72 h (IC50 of 0.23 and 0.15 µg/mL, respectively). The extract, fractions, and flavopereirine presented low toxicity, with high selectivity for the alkaloid. Furthermore, flavopereirine showed no violation of Lipinski's rule of five, showing even better results than the known inhibitor of oligopeptidase B, antipain, with three violations. Flavopereirine also interacted with residue Tyr-499 of oligopeptidase B during the molecular dynamics simulations, giving a few insights of a possible favorable mechanism of interaction and a possible inhibitory pathway. Flavopereirine proved to be a promising molecule for its antileishmanial activity.

Discovery of potent indoleamine 2,3-dioxygenase (IDO) inhibitor from alkaloids in Picrasma quassioides by virtual screening and in vitro evaluation.

Indoleamine 2,3-dioxygenase (IDO) is one of the important targets for cancer immunotherapy through tryptophan pathway. Recently it has being paid great attention to search potent and safe IDO inhibitor from small-molecule compounds. Picrasma quassioides is a kind of medicinal plant abundant with tryptophan-derived indole alkaloids. By virtual screening and kinetic method for enzymatic analysis, lead compounds with potential IDO inhibitory activity were discovered for the first time from PQAs, the natural alkaloids in Picrasma quassioides. The results based on molecular docking analysis and structure-activity relationship (SAR) study demonstrated that coordinating with ferrous ion on the active site of IDO has a great impact on the inhibition potency, and ß-carboline with carboxyl substituted on C-1 is the key pharmacophore for IDO inhibition of PQAs. Enzymatic assay provided further evidence for the effectiveness of ß-carboline-1-carboxylic acid, which displayed as the most potent competitive inhibitor of IDO among these PQAs, and is even more potent than the recognized positive control 1-methyl tryptophan. This natural tryptophan-derived alkaloid thus deserved further deep research as a promising IDO modulator for cancer immunotherapy.

Bioactivity-guided isolation of ß-Carboline alkaloids with potential anti-hepatoma effect from Picrasma quassioides (D. Don) Benn.

ß-Carboline alkaloids in Picrasma quassioides (D. Don) Benn. have been proven to possess inhibitory activity against various cancer cells. However, their effect on hepatocellular carcinoma and structure-activity relationships (SAR) have not been systematically reported. In this work, bioactivity-directed fractionation of P. quassioides led to the separation of active fraction A2-2. A total of 39 ß-carbolines, including 4 new ones (1-4), were obtained from the active fraction. Moreover, all the isolated compounds were identified in the active fraction A2-2 by LC-MS. The cytotoxicity on HepG2 and Hep3B cells of all compounds was screened by MTT assay, and the SAR were established. The SAR were also supported by the apoptosis ratio of HepG2 cells using flow cytometry analysis after treatment with potential compounds 1, 2, 9, 10, 12, 29, 36 and 38. It suggested that these active compounds caused death of hepatoma cells through apoptosis induction. In addition, further study revealed that compounds 12, 29, 36 significantly activated caspase-3 in HepG2 cells.

Two new ß-carboline alkaloids from the stems of Picrasma quassioides.

Two new ß-carboline alkaloids, 1-acetyl-4-methoxy-8-hydroxy-ß-carboline (1) and 1-acetyl-4,8-dimethoxy-ß-carboline (2), together with 10 known compounds; seven ß-carboline alkaloids (3-9), two canthin-6-one alkaloids (10 and 11), and one quassinoid (12) were isolated from the stems of Picrasma quassioides. The structure of the new compounds 1 and 2 were determined by spectroscopic analyses including 1D- and 2D-NMR and HRMS interpretation. All the isolates (1-12) were evaluated for their cytotoxicity against human ovarian carcinoma A2780 and SKOV3 cell lines using MTT assays. Of the isolates, compounds 5-7 exhibited the most potent cytotoxicity on both A2780 and SKOV3 cell lines in vitro.

Preparation and purification of canthinone and ß-carboline alkaloids from Picrasma quassioides based on bioautography and mass-spectrometry-directed autopurification system.

Picrasma quassioides (D. Don) Benn. is a widely used traditional Chinese medicine for anti-inflammation and antibiosis. Canthinone and ß-carboline alkaloids are the main characteristic constituents that possess diverse pharmacological effects, such as anti-inflammatory and anti-infectious properties. In this study, bioautography in thin-layer chromatography indicated that the antiradical activity compound may be alkaloids. Then, a simple, fast, and efficient method was established for the separation and purification of two types of alkaloids from P. quassioides by mass-spectrometry-directed autopurification system. Eight alkaloids were isolated and purified in this one-step methodology. Among them, five compounds (3, 95.1%, 58.8 mg; 4, 98.4%, 71.7 mg; 6, 97.8%, 365.4 mg; 7, 97.7%, 172.7 mg; 8, 98.2%, 180.3 mg) were obtained in large amounts with extremely high purities. Then, the antiradical activities of the isolates showed that 4-methoxy-5-hydroxycanthin-6-one (6) exhibited obvious 1,1-diphenyl-2-picryl-hydrazyl free radical scavenging activity with an IC50 value of 84.037 µM. This study offers a new method for the preparation of targeted bioactive alkaloids in P. quassioides. This work also provides a reference for the separation of other targeted chemical components with potential activities from traditional Chinese herbal medicines.

Anti-inflammatory Effects of Canthin-6-one Alkaloids from Ailanthus altissima.

Canthin-6-one (CO) alkaloids possess various biological activities, including antibacterial, antitumor, antifungal, and antiviral activities. However, their anti-inflammatory effects and underlying molecular mechanisms are poorly characterized. This study aimed to investigate the anti-inflammatory effects of CO and its derivative 5-(1-hydroxyethyl)-canthin-6-one (5-HCO), isolated from the stem barks of Ailanthus altissima in lipopolysaccharide (LPS)-stimulated macrophages. CO (1 and 5 µM) and 5-HCO (7.5 and 15 µM) significantly inhibited the LPS-induced expression of inducible nitric oxide synthase. In addition, CO (1 and 5 µM) and 5-HCO (15 µM) markedly suppressed the production of prostaglandin E2 (PGE2) and expression of cyclooxygenase-2, a key enzyme in PGE2 synthesis, in LPS-stimulated macrophages. Moreover, CO treatment significantly reduced monocyte chemotactic protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α) expression, whereas 5-HCO inhibited MCP-1, but not TNF-α expression. Both CO and 5-HCO inhibited the phosphorylation of inhibitor kappa B and transcriptional activation of nuclear factor kappa B (NF-κB) in LPS-stimulated macrophages. In addition, CO, but not 5-HCO, markedly reduced Akt phosphorylation. Taken together, these data suggest that CO, but not 5-HCO with a hydroxyethyl moiety on the D ring, has potent anti-inflammatory activity in LPS-stimulated macrophages through the downregulation of both the NF-κB and the Akt pathway.

A self-feedback network based on liquid chromatography-quadrupole-time of flight mass spectrometry for system identification of ß-carboline alkaloids in Picrasma quassioides.

Profiling chemical components in herbs by mass spectrometry is a challenging work because of the lack of standard compounds, especially for position isomers. This paper provides a strategy based on a self-feedback network of mass spectra (MS) data to identify chemical constituents in herbs by liquid chromatography-quadrupole-time of flight mass spectrometry without compound standards. Components sharing same skeleton were screened and all ions were classified into a database. All candidates were connected by the selected bridging ions to establish a primary MS network. Benefited from such a network, it is feasible to characterize sequentially the structures of all diagnostic ions and candidates once single component has been de novo identified. Taking Picrasma quassioides as an example, the primary network of ß-carbolines was established with 65 ions (selected from 76 ß-carbolines), each of which appeared at least in four compounds. Once an alkaloid has been identified, its logical ions could feedback into primary network to build pathways with other unknown compounds. Moreover, the position of the substituent groups could be deduced through the secondary metabolic pathways of alkaloids (plant secondary metabolism). The network therefore can be utilized for identification of unknown compounds and even their position isomers.

Anti-inflammatory bioactive equivalence of combinatorial components ß-carboline alkaloids identified in Arenaria kansuensis by two-dimensional chromatography and solid-phase extraction coupled with liquid-liquid extraction enrichment technology.

Bioactive equivalent combinatorial components play a critical role in herbal medicines. However, how to discover and enrich them efficiently is a question for herbal pharmaceuticals researchers. In our work, a novel two-dimensional reversed-phase/hydrophilic interaction high-performance liquid chromatography method was established to perform real-time components trapping and combining for preparation and isolation of coeluting components. Arenaria kansuensis was taken as an example, and solid-phase extraction coupled with liquid-liquid extraction as a simple and efficient method for enriching trace components, reversed phase column coupled with hydrophilic interaction liquid chromatography XAmide column as two-dimensional chromatography technology for isolation and preparation of coeluting constituents, enzyme-linked immune-sorbent assay as bio-guided assay, and anti-inflammatory bioactivity evaluation for bioactive constituents. A combination of 12 ß-carboline alkaloids was identified as anti-inflammatory bioactive equivalent combinatorial components from A. kansuensis, which accounts for 1.9% w/w of original A. kansuensis. This work answers the key question of which are real anti-inflammatory components from A. kansuensis and provides a fast and efficient approach for discovering and enriching trace ß-carboline alkaloids from herbal medicines for the first time. More importantly, the discovery of bioactive equivalent combinatorial components could improve the quality control of herbal products and inspire a herbal medicine based on combinatorial therapeutics.

Isolation of a new ß-carboline alkaloid from aerial parts of Triclisia sacleuxii and its antibacterial and cytotoxicity effects.

A new ß-carboline alkaloid named sacleuximine A (1) together with known compounds palmatine (2), isotetrandrine (3), trans-N-feruloyltyramine (4), trans-N-caffeoyltyramine (5), yangambin (6), syringaresinol (7), sesamin (8), (+) epi-quercitol (9), 4-hydroxybenzaldehyde (10), ß-sitosterol (11), quercetin 3-O-rutinoside (12) and myricetin 3-O-ß-glucose (1→6) α-rhamnoside (13) have been isolated from methanol extract of Triclisia sacleuxii aerial parts. Compounds 1-10 were evaluated for their cytotoxicity against human adenocarcinoma (HeLa), human hepatocarcinoma (Hep3B) and human breast carcinoma (MCF-7) cells lines and also for antibacterial activities against both Gram-positive and Gram-negative bacteria. The cytotoxicity (IC50) values ranged between 0.15 and 36.7 µM while the minimum inhibitory concentrations were found to be in the range of 3.9 and 125 µM, respectively. This is the first report of antibacterial compounds and the isolation of lignans together with a ß-carboline alkaloid from T. sacleuxii.

Indole Alkaloids from the Leaves of Nauclea officinalis.

Three new indole alkaloids, named naucleamide G (1), and nauclealomide B and C (5 and 6), were isolated from the n-BuOH-soluble fraction of an EtOH extract of the leaves of Nauclea officinalis, together with three known alkaloids, paratunamide C (2), paratunamide D (3) and paratunamide A (4). The structures with absolute configurations of the new compounds were identified on the basis of 1D and 2D NMR, HRESIMS, acid hydrolysis and quantum chemical circular dichroism (CD) calculation. According to the structures of isolated indole alkaloids, their plausible biosynthetic pathway was deduced.

A Series of ß-Carboline Alkaloids from the Seeds of Peganum harmala Show G-Quadruplex Interactions.

In this study, we screened 17 medicinal plants for binding activity to G-quadruplex d(TTGGGTT)4 by (1)H NMR spectroscopy and found that the crude extract of Peganum harmala L. seeds showed the most potential binding activity. Subsequently, (1)H NMR- and bioassay-guided isolation of the extract of P. harmala L. was performed to obtain four pairs of partially racemized ß-carboline alkaloids, pegaharmines A-D (1-4). Their structures and absolute configurations were determined by extensive NMR analyses, X-ray crystallography, ECD calculations, and CD exciton chirality approaches. Interestingly, pegaharmine D (4), which showed the strongest G-quadruplex interaction, exhibited significant cytotoxic activity against three cancer cell lines. This work contributed a practical strategy for the discovery of novel G-quadruplex ligands from natural products and provided potential insights for using ß-carboline alkaloids as anticancer lead compounds specifically targeting G-quadruplexes.

A new anti-inflammatory ß-carboline alkaloid from the hairy-root cultures of Eurycoma longifolia.

One new ß-carboline alkaloid 7-methoxy-(9H-ß-carbolin-1-il)-(E)-1-propenoic acid (1) together with 9-methoxycanthin-6-one (2) and 9-hydroxycanthin-6-one (3) were isolated from the hairy-root cultures of Eurycoma longifolia. The effects of these compounds on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 cells were investigated. Compound 1 strongly inhibited the production of NO while 2 and 3 having weak or inactive effect. Consistently, compound 1 decreased the expression of cyclooxygenase-2 and inducible nitric oxide synthase.

Constituents of the stem barks of Ailanthus altissima and their potential to inhibit LPS-induced nitric oxide production.

Three new canthinone type alkaloids, canthin-6-one-1-O-ß-D-apiofuranosyl-(1→2)-ß-D-glucopyranoside (1), canthin-6-one-1-O-[6-O-(3-hydroxy-3-methylglutaryl)]-ß-D-glucopyranoside (2) and canthin-6-one-1-O-[2-ß-D-apiofuranosyl-6-O-(3-hydroxy-3-methylglutaryl)]-ß-D-glucopyranoside (3) were isolated from the stem barks of Ailanthus altissima together with four quassinoids (4-7), seven phenylpropanoids (8-14) and a lignan of previously known structure (15). The inflammatory activities of the 15 isolates were screened on LPS-induced nitric oxide (NO), a proinflammatory mediator, in RAW 264.7 cells.

Design, synthesis, anti-TMV, fungicidal, and insecticidal activity evaluation of 1,2,3,4-tetrahydro-ß-carboline-3-carboxylic acid derivatives based on virus inhibitors of plant sources.

By drawing the creation ideas of botanical pesticides, a series of tetrahydro-ß-carboline-3-carboxylic acid derivatives were designed and synthesized, and first evaluated for their anti-TMV, fungicidal and insecticidal activities. Most of these derivatives exhibited good antiviral activity against TMV both in vitro and in vivo. Especially, the activities of compounds 8 and 15 in vivo were higher than that of ribavirin. The compound 8 exhibited more than 70% fungicidal activities against Cercospora arachidicola Hori, Alternaria solani, Bipolaris maydis, and Rhizoctonia solani at 50mg/kg, compounds 16 and 20 exhibited more than 60% insecticidal activities against Mythimna separate and Ostrinia nubilalis.