Melodinines M-U, cytotoxic alkaloids from Melodinus suaveolens

Nine new alkaloids, melodinines M-U (1-9), and 11 known alkaloids were isolated from Melodinus suaveolens. The new structures were elucidated by extensive NMR and mass spectroscopic analyses and comparison to known compounds. All compounds were evaluated for their cytotoxicity against five human cancer cell lines. Compounds 6, 11, and 16 showed significant cytotoxicity.     

Antiplasmodial activities of furoquinoline alkaloids from Teclea afzelii

The study of the chemical constituents of the stem bark of Teclea afzelii (Rutaceae) has resulted in the isolation and characterization of four furoquinoline alkaloids, namely kokusaginine (1), tecleaverdoornine (2), maculine (3) and montrifoline (4) together with lupeol (5) and b‐sitosterol glucopyranoside (6). The structures of the isolated compounds were elucidated based on spectroscopic studies. The antimalarial activity of compounds 1–4 against Plasmodium falciparum in vitro shows partial suppression of parasitic growth. Copyright © 2009 John Wiley & Sons, Ltd.     

Anti-HIV and cytotoxic alkaloids from Buchenavia capitata.

The anti-HIV activity in the organic solvent extract of leaves of Buchenavia capitata was traced to a series of known flavonoid alkaloids, which represent a new chemotype for anti-HIV activity. The 13C-nmr assignments for this series of compounds have been revised. O-Demethylbuchenavianine [1] was the most active compound of the series but produced only moderate cytoprotective effects against HIV in cultured human lymphoblastoid (CEM-SS) cells. Compound 1 was cytotoxic also in the NCI human disease-oriented in vitro tumor screening panel and produced a pattern of modest differential cellular sensitivity.     

Psammaplysenes C and D, cytotoxic alkaloids from Psammoclemma sp

The sponge Psammoclemma sp. was investigated as part of our studies to discover P2X 7 receptor antagonists for the treatment of inflammatory disease. The biological activity of this extract was found to be due to the cytotoxicity of two new bromotyrosine alkaloids, psammaplysenes C (1) and D (2), and not P2X 7-specific activity. Their structures were determined by 1D and 2D NMR spectroscopy.     

Antimalarial, cytotoxic, and antifungal alkaloids from Duguetia hadrantha

Bioassay-guided isolation of Duguetia hadrantha yielded two new 4,5-dioxo-1-azaaporphinoids, hadranthine A (1) and hadranthine B (2), together with the known alkaloids imbiline-1 (3), sampangine (4), and 3-methoxysampangine (5), whose structures were determined primarily from 2D-NMR 1H-13C HMBC, and 1H-15N HMBC experiments. This is the first report of the co-occurrence of the copyrine alkaloids 4 and 5, as well as the first report of either copyrine or imbiline type alkaloids from a Duguetia species. Compounds 1, 4, and 5 demonstrated in vitro antimalarial activity against Plasmodium falciparum (W-2 clone), while 2 was inactive. Instead, 2 showed in vitro cytotoxicity to selected human cancer cell lines (IC50 = 3-6 microg/mL against SK-MEL, KB, BT-549, and SK-OV-3), and 4 was also cytotoxic to human malignant melanoma (IC50 = 0.37 microg/mL). Sampangine (4) also inhibited cell aggregation with a MIC value of <0.15 microg/mL, while 3-methoxysampangine (5) was only weakly active.     

Jerantinines A-G, cytotoxic Aspidosperma alkaloids from Tabernaemontana corymbosa

Seven new indole alkaloids of the Aspidosperma type, jerantinines A-G (1-7), were isolated from a leaf extract of the Malayan Tabernaemontana corymbosa. The structures were established using NMR and MS analysis. Five of the alkaloids isolated and two derivatives (1-5, 8, 9) displayed pronounced in vitro cytotoxicity against human KB cells (IC50 < 1 microg/mL).     

Triterpenoidal alkaloids from Buxus natalensis and their acetylcholinesterase inhibitory activity

Acetylcholinesterase (AChE) inhibition-directed phytochemical studies on the methanolic extract of Buxus natalensis, collected in South Africa, resulted in the isolation of 12 compounds: O(2)-natafuranamine (1), O(10)-natafuranamine (2), cyclonataminol (3), 31-demethylbuxaminol A (4), buxaminol A (5), buxafuranamide (6), buxalongifolamidine (7), buxamine A (8), cyclobuxophylline K (9), buxaminol C (10), methyl syringate (11), and p-coumaroylputrescine (12). Compounds 1-4 were new alkaloids, and compound 5 was isolated for the first time as a natural product. Their structures were elucidated with the aid of extensive NMR and mass spectroscopic studies. Compounds 1 and 2 are members of a rarely occurring class of Buxus alkaloids, having a tetrahydrofuran ring incorporated in their structures. Compounds 1-12 exhibited strong to moderate AChE inhibitory activity.     

Cholinesterase inhibitory and anti-amnesic activity of alkaloids from Corydalis turtschaninovii

In the course of screening plants used in Korean folk medicine as memory enhancers, a 70% ethanol extract of tuber from Corydalis turtschaninovii Besser (Papaveraceae) showed significant acetylcholinesterase (AChE) inhibitory activity. Repeated column chromatography led to the isolation of a new aporphine alkaloid, oxoglaucidaline (9), and a new protoberberine, pseudodehydrocorydaline (13) together with 14 known compounds (1-8, 10-12, and 14-16). The chemical structures of isolated compounds were elucidated base on extensive 1D and 2D NMR spectroscopic data. Compounds 1-16 were investigated in vitro for their anti-cholinesterase activity using the mice cortex AChE enzyme. In further study, the anti-amnesic activities of pseudoberberine (16) in mice on the learning and memory impairments induced by scopolamine (1.0mg/kg, i.p.) were examined. This alkaloid (5.0mg/kg, p.o.) administration significantly reversed cognitive impairments in mice by passive avoidance test (P<0.05). It also reduced escape latencies in training trials and prolonged swimming times in the target quadrant during the probe trial in the water maze task (P<0.05). These results indicated that Corydalis turtschaninovii due to its alkaloids have anti-cholinesterase activity and pseudoberberine and other alkaloids have anti-amnesic activities that may be useful for cognitive impairment treatment.     

New cytotoxic indole alkaloids from Tabernaemontana calcarea from the Madagascar rainforest

Bioassay-directed fractionation of the alkaloid portion of a CH(2)Cl(2)-MeOH extract of Tabernaemontana calcarea resulted in the isolation of the three new cytotoxic indole alkaloids, 1-3, and the 12 known alkaloids voacangine (4), isovoacangine (5), coronaridine (6), 11-hydroxycoronaridine (7), voacristine (8), 19-epi-voacristine (9), isovoacristine (10), ibogamine (11), 10-methoxyibogamine (12), 11-methoxyibogamine (13), heyneanine (14), and 19-epi-heyneanine (15). The structures of the new compounds 1-3 were elucidated on the basis of extensive 1D and 2D NMR spectroscopic interpretation. All the compounds exhibited cytotoxic activity against the A2780 ovarian cancer cell line.     

New cytotoxic steroidal alkaloids from the Philippine sponge Corticium niger

Four new steroidal alkaloids, plakinamine I-K (1-3) and dihydroplakinamine K (4), were isolated from the marine sponge Corticium niger. The structures of these compounds were elucidated by interpretation of spectroscopic data. Compounds 1-4 exhibit significant in vitro cytotoxicity.     

Discorhabdins I and L, cytotoxic alkaloids from the sponge Latrunculia brevis

Two cytotoxic alkaloids, discorhabdins L (1) and I (2), were isolated from Latrunculia brevis and their structures assigned on the basis of detailed spectroscopic analysis and comparison with the known metabolites discorhabdins R (5), D (6), and B (4). Compounds 1 and 2 showed strong in vitro cytotoxicity against a panel of 14 tumor cell lines.     

Hyrtioerectines A-C, cytotoxic alkaloids from the red sea sponge hyrtioserectus

A Red Sea specimen of the marine sponge Hyrtios erectus was found to contain three new alkaloids, hyrtioerectines A-C (1-3). Hyrtioerectine A (1) possesses the carbon bond-linked moieties 6-hydroxy beta-carboline and 6-hydroxyindole. The structure elucidation of 1-3 was based on intensive study of their spectral data including 1D (1H and 13C) and 2D (1H-1H COSY, HOHAHA, NOESY, ROESY, HMQC, and HMBC) NMR, together with high-resolution mass spectra. Hyrtioerectines A-C were moderately cytotoxic.     

Lipoperoxidation and cyclooxygenase enzyme inhibitory piperidine alkaloids from Cassia spectabilis green fruits

Phytochemical work in the search for bioactive metabolites from the methanolic extract of Senna spectabilis green fruits led to the isolation of a new piperidine alkaloid, (+)-3- O-feruloylcassine ( 1), in addition to the known (-)-spectaline ( 2) and (-)-3- O-acetylspectaline ( 3). The isolates were submitted to in vitro evaluation of lipoperoxidation (LPO) and cyclooxygenase enzymes (COX-1 and -2) inhibitory properties and showed moderate antioxidant activities (40-70%) at 100 ppm when compared to commercial standards BHT and vitamin E and moderate inhibition of COX-1 (ca . 40%) and marginal inhibition of COX-2 enzymes (<10%) at 100 ppm when compared to nonsteroidal anti-inflammatory drugs (NSAIDs) aspirin, rofecoxib, and celecoxib, respectively.     

New cytotoxic alkaloids from the wood of Vepris punctata from the Madagascar rainforest

Bioassay-guided fractionation of a CH(2)Cl(2)/MeOH extract of the wood of Vepris punctata resulted in the isolation of three new furoquinoline alkaloids, 5-methoxymaculine (1), 5,8-dimethoxymaculine (2), and 4,5,6,7,8-pentamethoxyfuroquinoline (3), in addition to the four known alkaloids flindersiamine (4), kokusaginine (5), maculine (6), and skimmianine (7). The structures of the new alkaloids 1-3 were established on the basis of extensive 1D and 2D NMR spectroscopic data interpretation. All the isolated compounds were tested against the A2780 human ovarian cancer cell line, and all seven alkaloids showed weak cytotoxic activity.     

Two new natural azafluorene alkaloids and a cytotoxic aporphine alkaloid from Polyalthia longifolia

The stem and stem bark of Polyalthia longifolia afforded the cytotoxic aporphine alkaloid liriodenine [1], as well as two aporphine alkaloids, noroliveroline [2] and oliveroline-beta-N-oxide [3] and three azafluorene alkaloids, darienine [4], polyfothine [6], and isooncodine [7], which are not bioactive. Polyfothine [6] and isooncodine [7] are new natural compounds.     

Quinolone alkaloids with nitric oxide production inhibitory activity from Orixa japonica

Four new quinolone alkaloids, orixalone A (1), B (2), C (3), and D (4), together with 12 known compounds were isolated from the stems of Orixa japonica. Orixalone A (1) inhibited nitric oxide production in murine macrophage-like RAW 264.7 cells stimulated with interferon-gamma and lipopolysaccharide.     

Claurailas A-D, cytotoxic carbazole alkaloids from the roots of Clausena harmandiana

Four new carbazole alkaloids, claurailas A-D (1-4), as well as 12 known carbazoles and three known coumarins were isolated from the roots of Clausena harmandiana. Heptaphylline (6) and 7-methoxyheptaphylline (7) showed strong cytotoxicity against NCI-H187 and KB cell lines with IC(50) values ranging from 1.3 to 2.7 μM. Compound 7 showed no cytotoxicity against Vero cells.     

New cytotoxic N-methylated beta-carboline alkaloids from the marine ascidian Eudistoma gilboverde.

Bioassay-guided fractionation of an extract of the marine ascidian Eudistoma gilboverde provided three new beta-carboline alkaloids identified as 2-methyleudistomin D (1), 2-methyleudistomin J (2), and 14-methyleudistomidin C (3). Six known metabolites, eudistomins C, D (4), E, J (5), K, and L, were also isolated and characterized. The structures of the new metabolites were elucidated by spectroscopic analyses and by comparison of their spectral data with related literature values. Of the three new compounds, 14-methyleudistomidin C (3) exhibited the most potent cytotoxic activity with IC(50)'s of < 1.0 microg/mL against four different human tumor cell lines.     

New cytotoxic beta-carboline alkaloids from the marine bryozoan, Cribricellina cribraria.

Bioactivity-directed separations led to the isolation of the new alkaloid, 1-vinyl-8-hydroxy-beta-carboline [1], as the major cytotoxic component of the marine bryozoan Cribricellina cribraria. Another new beta-carboline alkaloid 2 with the novel sulfone structure was isolated, together with a number of known beta-carboline compounds. Cytotoxicity and antimicrobial effects are reported for these compounds and for other synthesized beta-carbolines.     

Micromide and guamamide: cytotoxic alkaloids from a species of the marine cyanobacterium Symploca

Two new cytotoxins have been isolated from a species of marine cyanobacterium belonging to the genus Symploca that was collected in Guam. These new compounds, micromide (1) and guamamide (2), were accompanied by the known lipopeptides apramides A (3), B (4), and G (5). The planar structures of both alkaloids were elucidated by standard 2D NMR techniques, and the configurations of the amino acid-derived units in 1 were determined by chiral HPLC. The stereochemistry of the beta-methoxyhexanoic acid in 1 was determined by derivatization with methyl d-mandelate, after acid hydrolysis, and comparison with synthetic standards.