Cytotoxicity of Rhamnosylanthraquinones and Rhamnosylanthrones from Rhamnus nepalensis.

An extract of the fruits of Rhamnus nepalensis collected in Hoa Binh Province, Vietnam, was cytotoxic to KB cells. A bioassay-guided fractionation led to the isolation of a series of known anthraquinones and anthrones, one new rhamnosylanthraquinone, 3'-O-acetylfrangulin A (8), several new rhamnosylanthrones, the prinoidin-emodin bianthrones (9A-D), the prinoidin bianthrones (10A,B), and the rhamnepalins (11A-C). A structure-cytotoxic activity relationship study was performed on these isolates and some semisynthetic derivatives.

A new diprenyl coumarin and alkaloids from the bark of Zanthoxylum dimorphophyllum (Rutaceae).

The alkaloids chelerythrine, norchelerythrine, oxyavicine, canthine-6-one, 4,5-dihydrocanthin-6-one, and gamma-fagarine were isolated from Zanthoxylum dimorphophyllum bark, together with two coumarins, scoparone and dimoxylin. This latter is a novel compound whose structure was elucidated on the basis of its spectral data.

Furomegistines I and II, two furanopyridine alkaloids from the bark of Sarcomelicope megistophylla.

Two alkaloids, furomegistine I (1) and furomegistine II (2), were isolated from the bark of Sarcomelicope megistophylla. Their structures have been elucidated on the basis of MS and NMR data. Both belong to the category of furanopyridine alkaloids and should be considered as oxidation products of a furo[2,3-b]quinoline precursor. The two alkaloids exhibited moderate cytotoxic activity.

Triterpenoid saponins from the stem bark of Elattostachys apetala.

Six new triterpenoid saponins have been isolated from the stem bark of Elattostachys apetala together with four known triterpenoid saponins. Three of these new compounds are glycosides of a newly described genin, 29-hydroxyhederagenin (1). On the basis of spectral evidence, the structures of the new saponins were concluded to be alpha-hederin 28-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl] ester (2), sapindoside B 28-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl] ester (3), 3-O-beta-D-xylopyranosyl astrantiasaponin VII (4), 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl]-28-O-[beta-D-glucopyranosyl-(1-->2)-[beta-D-glucopyranosyl-(1-->6)]-beta-D-glucopyranosyl]-29-hydroxyhederagenin (5), 3-O-[alpha-L-arabinopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl]-28-O-[beta-D-glucopyranosyl(1-->2)-[beta-D-glucopyranosyl(1-->6)]-beta-D-glucopyranosyl]-29-hydroxyhederagenin (6), and 3-O-[beta-D-xylopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl]-28-O-[beta-D-glucopyranosyl-(1-->2)-beta-D-gluco pyranosyl-(1-->6)]-beta-D-glucopyranosyl]-29-hydroxyhederagenin (7).

Novel cytotoxic 4-phenylfuranocoumarins from Calophyllum dispar.

Eight new 4-phenylfuranocoumarins (1-8) have been isolated from the stem bark and the fruits of Calophyllum dispar, together with three known coumarins. The structures of 1-8 were established by means of spectroscopic analysis, including extensive 2D NMR studies. Some of these furanocoumarins exhibited significant cytotoxic activity against KB cells.

New xanthones from Calophyllum caledonicum.

Four new xanthones, caledonixanthones A-D (1-4), were isolated from the trunk bark of Calophyllum caledonicum, in addition to 17 known compounds. The structures of 1-4 were determined by means of spectroscopic analysis and chemical derivatization.

Structure-activity relationship of polyisoprenyl benzophenones from Garcinia pyrifera on the tubulin/microtubule system.

Microtubule disassembly inhibitory properties have been established for the known polyisoprenylated benzophenones xanthochymol (1a) and guttiferone E (1b). The compounds were isolated from the fruits of Garcinia pyrifera collected in Malaysia. A structure-activity relationship study, including natural and semisynthetic derivatives, delineated some structural features necessary for the interaction with tubulin within this compound class.

The structure of sarcomejine: an application of long-range (1)H-(15)N correlation at natural abundance.

A new 4(1H)-quinolinone alkaloid, sarcomejine (1), has been isolated from the bark of Sarcomelicope megistophylla. Its structure has been elucidated on the basis of MS and NMR data and especially with a long-range (1)H-(15)N correlation NMR spectrum at natural abundance.

Effects of triterpenes from the stem bark of Dysoxylum cauliflorum on a non-small-cell bronchopulmonary carcinoma cell line (NSCLC-N6).

Six triterpenoids and one sesquiterpene were isolated from the ethanolic extract of the stem bark of Dysoxylum cauliflorum. Their structures were determined from 1D and 2D NMR and mass spectral data. Only compound 1 was cytostatic. Kinetic studies with ethyl eichlerianoate 1 demonstrated that this growth arrest was irreversible and cytofluorimetric analysis with compound 1 showed a complete block of NSCLC-N6 cells in the G1 phase. These events were related to a terminal maturation induction.

Two new alkaloids from the bark of Sarcomelicope megistophylla.

Two new alkaloids, megistophylline I (1) and megistophylline II (2), were isolated from the bark of Sarcomelicope megistophylla. Their structures have been elucidated on the basis of MS and NMR data.

Cytotoxic prenylxanthones from Garcinia bracteata.

Bioassay-guided fractionation of a leaf extract of G. bracteata has yielded six new prenylxanthones, bractatin (1), isobractatin (2), 1-O-methylbractatin (3), 1-O-methylisobractatin (4), 1-O-methyl-8-methoxy-8,8a-dihydrobractatin (5), and 1-O-methylneobractatin (6). The structures of these compounds have been elucidated by spectroscopic means (NMR, MS), literature data, and X-ray crystallographic analysis of 2. These compounds possess significant cytotoxicity against the KB cell line.

Two new 3-methoxy-4-quinolone alkaloids from the bark of Sarcomelicope megistophylla.

Two new alkaloids, megistonine I (1) and megistonine II (2), were isolated from the bark of Sarcomelelicope megistophylla. Their structures, which are derived from the 3-methoxy-4-quinolone basic skeleton, were elucidated on the basis of MS and extensive NMR studies.

Megistolactone, a new alkaloid from Sarcomelicope megistophylla.

A new quinolone alkaloid, megistolactone (1) was isolated from the bark of Sarcomelicope megistophylla. Its structure has been elucidated on the basis of MS and NMR data. From a biogenetic point of view, this compound should be considered as an oxidation product of 1,2,3,4-tetra-O-subsituted acridone alkaloids, which are also present in the bark.

Polyoxygenated flavones from the leaves of comptonella microcarpa

The leaves of Comptonella microcarpa have yielded one alkaloid, dictamnine, and four known polyoxygenated flavonoids, meliternatin, 3,5,8-trimethoxy-6,7-3',4'-dimethylenedioxyflavone, 7-(3-methylbut-2-enyloxy)-3,5,8-trimethoxy-3', 4'-methylenedioxyflavone (3), 7-hydroxy-3,5,8-trimethoxy-3', 4'methylenedioxyflavone. In addition, two new flavonoids were found whose structures were established on the basis of their spectral data as 7-hydroxy-3,5,6,8-tetramethoxy-3',4'-methylenedioxyflavone (1) and 7-(3-methylbut-2-enyloxy)-3,5,6,8-tetramethoxy-3', 4'-methylenedioxyflavone (2).

Rubiginoside, a farnesyl glycoside from Lepisanthes rubiginosa.

Chemical investigation of the methanolic fraction of Lepisanthes rubiginosa bark has led to the isolation and characterisation of a new tetrasaccharide derivative of farnesol named rubiginoside along with known triterpenoid saponins.

Pyrrolidinoindoline alkaloids from Psychotria oleoides and Psychotria lyciiflora.

The chemical study of two Rubiaceae from New Caledonia, Psychotria lyciiflora and Psychotria oleoides, led to the isolation of several pyrrolidinoindoline alkaloids. Two dimers, the known meso-chimonanthine (9) and the new Nb-desmethyl-meso-chimonanthine (5), and a known trimer, hodgkinsine (1), have been isolated from P. lyciiflora. Hodgkinsine (1), quadrigemine C (2), isopsychotridine B (3), psychotridine (4), and three new alkaloids, quadrigemine I (6), oleoidine (7), and caledonine (8), have been isolated from P. oleoides. Structural assignments of the compounds were based on mass spectra analysis and 2D NMR experiments. A tentative stereochemical determination is made from 2D NMR experiments, circular dichroism study and chemical correlations. Some of these compounds are functional antagonists of somatostatine (SRIH).

Cytotoxic 3,4-secoapotirucallanes from Aaglaia argentea bark.

Nine 3,4-secoapotirucallanes, argentinic acids A-I, were isolated from the bark of Aglaia argentea and transformed to their methyl esters 1-9. The structures were determined by spectral and chemical means. Compounds 1-8 showed moderate cytotoxic activity against KB cells (IC50 1.0-3.5 microg/mL).

Six triterpenoid saponins from Mmaesa laxiflora.

Six new triterpenoid saponins, maelaxins A-F (1-6), were isolated from a n-BuOH extract of the leaves of Maesa laxiflora. They possess 22-O-angeloyl-camelliagenin A, 16-O-acetyl, 22-O-angeloyl-camelliagenin A, or 22-O-(2Z)-hexenoyl-camelliagenin A as the aglycon. The pentasaccharide moiety linked to C-3 of the aglycon consists of D-glucuronic acid, L-rhamnose, D-glucose, and/or D-galactose. Their structures were elucidated by extensive NMR experiments including 1H-1H (COSY, 2D HOHAHA, NOESY) and 1H-13C (HMQC and HMBC) spectroscopy and chemical evidence.

Five new flavone 5-O-glycosides from Lethedon tannaensis: lethedosides and lethediosides.

Five new 7-methoxy-flavone 5-O-glycosides were isolated from a cytotoxic MeOH extract of Lethedon tannaensis, and the structures were elucidated by 2D NMR spectral analysis and by chemical methods. Lethedosides A (1), B (2), and C (3) were 5-O-glucosides of 7,3', 4'-tri-O-methylluteolin, 7,3',4',5'-tetra-O-methyltricetin, and 7,3', 4'-tri-O-methytricetin, respectively; lethediosides A (4) and B (5) and a known compound 6 were 5-O-xylosylglucosides of 7,3', 4'-tri-O-methylluteolin, 7,3',4',5'-tetra-O-methyltricetin, and 7, 4'-di-O-methylapigenin, respectively. These flavonoids were either inactive or weakly active against KB tumor cells, in contrast to previously isolated flavones from the same plant.

Cytotoxic polyisoprenes and glycosides of long-chain fatty alcohols from Dimocarpus fumatus.

The ethanolic extract from the stem bark of Dimocarpus fumatus, showed in vitro cytotoxic activity against KB cells. Fractionation of the extract gave compounds belonging to different classes. The two major components have been identified as a benzoquinone, sargaquinone, and a chromene, sargaol. One sphingolipid, soyacerebroside I, two glycosides of sitosterol, and fatty acids were also identified. Besides these known compounds, two new glycosides of long-chain fatty alcohols have been identified as 1-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D- glucopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->6)-beta-D- glucopyranosyl]hexadecanol and 1-O-[[alpha-L-arabinopyranosyl-(1-->3)]-alpha-L-rhamnopyranosyl-(1 -->2)- beta-D-glucopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->6)-beta-D- glucopyranosyl] hexadecanol, and a mixture of three new diacylglycerylglucosides has been isolated. These structures were elucidated by analysis of 2D-NMR and mass spectra.