Macrocyclic pyrrolizidine alkaloids from Senecio anonymus. Separation of a complex alkaloid extract using droplet counter-current chromatography

Ten 12-membered macrocyclic pyrrolizidine alkaloids, all of them esters of the necines, retronecine or otonecine, have been isolated from Senecio anonymus. The separation, carried out by droplet counter-current chromatography, afforded senecionine [1], integerrimine [2], retrorsine [3], senkirkine [5], neosenkirkine [6], otosenine [10], hydroxysenkirkine [7], and a new alkaloid given the trivial name anonamine [9]. Traces of usaramine [4] and another new alkaloid, hydroxyneosenkirkine [8], were detected by 1H nmr. In addition, the previously unreported 3a beta-hydroxy-4-ethoxy-2,6-perhydroindoledione [11] was isolated. X-ray structures were obtained for neosenkirkine [6], hydroxysenkirkine [7], anonamine [9], and [11]. 1H-13C heteronuclear shift correlated nmr (HETCOR) provided unambiguous chemical shift assignments for 13C-nmr data. Antitumor activity was assayed using the A204-rhabdomyosarcoma cell line in soft agarose.     

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.     

New humantenine-type alkaloids from Gelsemium elegans

The alkaloid extract of the whole plant of Gelsemium elegans has afforded four new alkaloids: N-desmethoxyrankinidine [1], 11-hydroxrankinidine [3], 11-hydroxyhuman-humantenine [4] and humantenirine [6]. The structures of 5 was established through X-ray crystallographic analysis, and the structures of the other three new alkaloids were deduced by spectral analysis (1H, 13C, APT, 2D-COSY and 2D-HETCOR).     

Two new styryl lactones, 9-deoxygoniopypyrone and 7-epi-goniofufurone, from Goniothalamus giganteus.

Two new styryl lactones, 9-deoxygoniopypyrone [1] and 7-epi-goniofufurone [3], and a known styryl lactone, goniodiol [5], were isolated from the stem bark of Goniothalamus giganteus. The structures were elucidated by ir, ms, 1H-nmr, 13C-nmr, and 1H-1H COSY spectra; the relative configurations were determined by X-ray crystallographic analysis. Unlike goniopypyrone [2] and goniofufurone [4], neither of the new styryl lactones 1 and 3 showed significant bioactivities to human tumor cells. However, goniodiol [5] showed significant and selective cytotoxicity against human lung tumor cells (A-549).     

New hydroxylated benzo[c]phenanthridine alkaloids from Eschscholtzia californica cell suspension cultures

From cell cultures of Eschscholtzia californica and their spent medium, three new benzo[c]phenanthridine alkaloids--namely 10-hydroxysanguinarine [2a], 12-hydroxychelirubine [4a], and 10-hydroxychelerythrine [7a]--and two new dihydrobenzo[c]phenanthridine alkaloids--10-hydroxydihydrosanguinarine [2b] and 12-hydroxydihydrochelirubine [4b]--together with the known constituents sanguinarine [1a], chelirubine [3a], macarpine [5a], dihydrosanguinarine [1b], dihydrochelirubine [3b], and dihydromacarpine [5b], were isolated and characterized. Structure elucidations were done by 1H nmr, decoupling experiments, and NOESY spectra. Isolated microsomes from E. californica, the site of hydroxylation activity within the cells, contained the whole set 1b to 8b of 5,6-dihydrobenzo[c]phenanthridines. A scheme for the biosynthesis of macarpine [5a] from protopine [9] via dihydrosanguinarine [1b] is presented.     

New amide alkaloids from the roots of Piper nigrum

Seven new amide alkaloids, named N-isobutyl-4-hexanoyl-4-hydroxypyrrolidin-1-one (1), (+/-)-erythro-1-(1-oxo-4,5-dihydroxy-2E-decaenyl)piperidine (2), (+/-)-threo-1-(1- oxo-4,5-dihydroxy-2E-decaenyl)piperidine (3), (+/-)-threo-N-isobutyl-4,5-dihydroxy-2E-octaenamide (4), 1-(1,6-dioxo-2E,4E-decadienyl)piperidine (5), 1-[1-oxo-3(3,4-methylenedioxy-5-methoxyphenyl)-2Z-propenyl]piperidine (6), and 1-[1-oxo-5(3,4-methylenedioxyphenyl)-2Z,4E-pentadienyl]pyrrolidine (7), were isolated from the roots of Piper nigrum, together with 32 known amides. Their structures were elucidated on the basis of spectroscopic analysis and chemical evidence.     

1H- and 13C-nmr assignments for taxol, 7-epi-taxol, and cephalomannine.

The 1H- and 13C-nmr spectra of taxol [1], 7-epi-taxol [2], and cephalomannine [3] were assigned using modern 1D and 2D nmr methods. Preliminary conformational information was obtained by nOe spectroscopy.     

Plant antitumor agents, 27. Isolation, structure, and structure activity relationships of alkaloids from Fagara macrophylla

The known alkaloids nitidine chloride [1] and 6-oxynitidine [2] and a new compound 6-methoxy-5,6-dihydronitidine [3] have been isolated from Fagara macrophylla. Compound 3 was the major product and was shown to be an artifact. The alkaloids 1 and 3 have been interconverted by treatment of 1 under basic conditions or 3 under acidic conditions. On sublimation 1 and 3 formed 8,9-dimethoxy-2,3-methylenedioxybenzo[c]phenanthridine [4] which could then be converted to 5,6-dihydronitidine [5]. The alkaloids 1 and 3 are about equipotent in P-388 mouse leukemia, giving high T/C values of 240-260% at doses of 30-50 mg/kg. The other compounds were inactive. The structural requirement for antitumor activity in the phenanthridine series is the ability to form a C-6 iminium ion.     

Pyrrolizidine alkaloids from Heliotropium rotundifolium

Heliotropium rotundifolium was shown to contain, in addition to the previously isolated europine [1], three other alkaloids: heliotrine [2], lasiocarpine [3], and a new alkaloid identified as 5'-acetyleuropine [4]. The alkaloids were isolated by dccc and the structures established by spectroscopic means (1H and 1H- 13CHETCOR nmr and ms), physical properties (melting points and/or optical rotations), comparison with authentic samples, or by semi-synthesis.     

Akuammine and dihydroakuammine, two indolomonoterpene alkaloids displaying affinity for opioid receptors.

Akuammine [1], an indolomonoterpene alkaloid, which is the major component of the seeds of Picralima nitida, was reduced to dihydroakuammine [4]. This compound has structural analogy with eseroline [7], for which affinity for opiate receptors was reported. The present investigation showed that 1 and 4 also bind (with lower affinity however) to mu and kappa opiate receptors. 1H- and 13C-nmr spectra of 1 and 4 have been fully assigned by 2D nmr experiments.     

7-deoxy-6-epi-castanospermine, a trihydroxyindolizidine alkaloid glycosidase inhibitor from Castanospermum australe

A new indolizidine alkaloid has been isolated from the seeds of Castanospermum [1] australe and identified as 7-deoxy-6-epi-castanospermine by ms and 1H- and 13C-nmr spectroscopy. The alkaloid is the first trihydroxylated indolizidine to be isolated from this plant and may represent an intermediate in the biosynthetic pathway to the tetrahydroxy-indolizidines and -pyrrolizidines. It inhibits amyloglucosidase and yeast alpha-glucosidase but is significantly less active as a glycosidase inhibitor than its isomer swainsonine [2] and the tetrahydroxylated alkaloids castanospermine [3], 6-epi-castanospermine [4], and australine [5].     

Kinmoonosides A-C, three new cytotoxic saponins from the fruits of Acacia concinna, a medicinal plant collected in myanmar

Three genuine saponins, named kinmoonosides A-C (1-3), have been isolated, together with a new monoterpenoid (4), from a methanolic extract of the fruits of Acacia concinna. The structures of kinmoonosides A-C were elucidated on the basis of spectral analysis as 3-O-?alpha-L-arabinopyranosyl(1-->6)-[beta-D-glucopyranosyl(1-->2) ]-b eta-D-glucopyranosyl?-21-O-?(6R, 2E)-2-hydroxymethyl-6-methyl-6-O-[4-O-(2'E)-6'-hydroxyl-2'-hydroxymet hyl-6'-methyl-2',7'-octadienoyl-beta-D-quinovopyranosyl]-2, 7-octadienoyl?acacic acid 28-O-alpha-L-arabinofuranosyl(1-->4)-[beta-D-glucopyranosyl(1-->3)]-a lpha-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranosyl ester (1); 3-O-?alpha-L-arabinopyranosyl(1-->6)-[beta-D-glucopyranosyl(1-->2) ]-b eta-D-glucopyranosyl?-21-O-?(6S, 2E)-2-hydroxymethyl-6-methyl-6-O-[4-O-(2'E)-6'-hydroxyl-2'-hydroxymet hyl-6'-methyl-2',7'-octadienoyl-beta-D-quinobopyranosyl]-2, 7-octadienoyl?acacic acid 28-O-alpha-L-arabinofuranosyl(1-->4)-[beta-D-glucopyranosyl(1-->3)]-a lpha-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranosyl ester (2); and 3-O-?alpha-L-arabinopyranosyl(1-->6)-[beta-D-glucopyranosyl(1-->2) ]-b eta-D-glucopyranosyl?-21-O-[(2E)-6-hydroxyl-2-hydroxymethyl-6-methyl- 2,7-octadienoyl]acacic acid 28-O-alpha-L-arabinofuranosyl(1-->4)-[beta-D-glucopyranosyl(1-->3)]-a lpha-L-rhamnopyranosyl(1-->2)-beta-D-glucopyranosyl ester (3), respectively. The new monoterpenoid 4 was determined as 4-O-[(2E)-6-hydroxyl-2-hydroxymethyl-6-methyl-2, 7-octadienoyl]-D-quinovopyranose. Compounds 1-3 showed significant cytotoxicity against human HT-1080 fibrosarcoma cells.     

Isolation, structure, and synthesis of novel 4-quinolinone alkaloids from Esenbeckia leiocarpa

Two new biocidal quinolinone alkaloids, 3-methoxy-1-methyl-2-propyl-4-quinolone [1] and 2(1'-ethylpropyl)-1-methyl-4-quinolone [2], were efficiently isolated using reversed-phase recycling hplc from the leaves of Esenbeckia leiocarpa. The structures were determined through spectroscopic data and confirmed by total synthesis. These alkaloids have antifeedant activities against the pink bollworm, Pectinophora gossypiella.     

Isolation of gelsedine-type indole alkaloids from Gelsemium elegans and evaluation of the cytotoxic activity of gelsemium alkaloids for A431 epidermoid carcinoma cells

Four new gelsedine-type indole alkaloids (1-4) were isolated from the leaves of Gelsemium elegans, together with 11 known alkaloids. The structures were determined as 14-acetoxygelsenicine (1), 14-acetoxy-15-hydroxygelsenicine (2), 14-hydroxy-19-oxogelsenicine (3), and 14-acetoxygelselegine (4), respectively, by spectroscopic analysis. The cytotoxic effects of 14 Gelsemium alkaloids including two new compounds (1, 2) were evaluated using the A431 human epidermoid carcinoma cell line. Of these, the gelsedine-type alkaloids 14-acetoxy15-hydroxygelsenicine (2) [corrected] 14,15-dihydroxygelsenicine (5), gelsedine (7), and gelsemicine (8) showed potent cytotoxic effects.     

Spermine alkaloids from Schweinfurthia papilionacea

Two new macrocylic alkaloids, 11-epi-ephedradine A (11-epi-orantine) [1] and schweinine [2], were isolated from the whole plant of Schweinfurthia papilionacea, in addition to (-)-ephedradine A (orantine) [3]. Their structures were determined by spectroscopic means, and the stereochemistry has been assigned on the basis of 2D nmr techniques.     

Microbial transformation studies on arteannuin B

The microbial transformation of the sesquiterpene lactone arreannuin B [3] using Aspergillus flavipes produced dihydroarteannuin B [4] as the main transformation product. Preparative-scale fermentation of 3 with Beauveria bassiana, on the other hand, has resulted in the production of two metabolites, 3 beta-hydroxyarteannuin B [5] and 13-hydroxy-11-epi-dihydroarteannuin B [6]. The structure of these metabolites, all of which are new compounds, was established using chemical and spectroscopic techniques. The isomeric dihydrocompound, 11-epi-dihydroarteannuin B [7] and an isomer of arteannuin B [8] were also prepared chemically. All compounds were subjected to 2D-nmr experiments and full 1H- and 13C-nmr assignments were made.     

New quinoline alkaloids from Ruta chalepensis

The roots of Ruta chalepensis, collected from the northern Saudi desert, yielded two new quinoline alkaloids, namely, 2-?6'-(2H-benzo[d]1' ',3' '-dioxolen-5' '-yl)hexyl?-hydroquinolin-4-one (1) and 2-?6'-(2H-benzo[d]1' ',3' '-dioxolen-5' '-yl)hexyl?-4-methoxy-quinoline (2). Nine previously reported alkaloids, dictamnine, pteleine, skimmianine, rutacridone, isogravacridonechlorine, maculosidine, graveoline, graveolinine, and 4-methoxy-1-methyl-2(1H)-quinolinone, and coumarins, chalepensin, and umbelliferone were also isolated. Structure elucidations were based primarily on 1D and 2D NMR analyses and chemical transformations. Antimicrobial activity of these compounds is discussed.     

Partial synthesis and antitubulin activity of minor colchicum alkaloids: N-acetoacetyl-deacetylcolchicine and 2-demethylspeciosine (speciocolchine)

Two minor Colchicum alkaloids, N-acetoacetyl-deacetylcolchicine [1] and 2-demethylspeciosine [7], were synthesized. The diacetate 8 of 2-demethylspeciosine was also prepared. The antitubulin activity of these compounds, in comparison to colchicine, was measured. N-Acetoacetyl-deacetylcolchicine [1] has in vitro activity similar to that of colchicine. Both 2-demethylspeciosine [7] and the diacetate 8 were considerably less potent inhibitors of tubulin polymerization.     

Cytotoxic flavaglines and bisamides from Aglaia edulis

Two new cyclopenta[b]benzofurans, aglaroxin A 1-O-acetate (2) and 3'-methoxyaglaroxin A 1-O-acetate (3), a new benzo[b]oxepine, 19,20-dehydroedulisone A (4), and five new cyclopenta[bc]benzopyrans, edulirin A (5), edulirin A 10-O-acetate (6), 19,20-dehydroedulirin A (7), isoedulirin A (8), and edulirin B (9), were isolated from the bark of Aglaia edulis, along with one known cyclopenta[b]benzofuran, aglaroxin A (1). Additionally, four new amides, aglamides A-D (10-13), as well as three known compounds, aglalactone, scopoletin, and 5-hydroxy-3,6,7,4'-tetramethoxyflavone, were isolated from the leaves and/or twigs of this species. The structures of the new compounds (2-13) were elucidated by interpretation of their spectroscopic data. All isolates obtained in this study were evaluated for cytotoxicity against both several human cancer cell lines (Lu1, LNCaP, and MCF-7) and a nontumorigenic (HUVEC) cell line. Among these isolates, the cyclopenta[b]benzofurans (1-3) exhibited potent in vitro cytotoxic activity (ED50 range 0.001 to 0.8 microg/mL). Aglaroxin A 1-O-acetate (2) was further evaluated in the in vivo P388 lymphocytic leukemia model, by intraperitoneal injection, but found to be inactive in this model.