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.

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.

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.

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.

Experimental study of antidiarrheal activity of Salicairine.

Experimental antidiarrheal activity of a traditionally used medication, Salicairine, was demonstrated in comparison to loperamide by significant inhibition of castor oil-induced diarrhea in mice (increases in hard faeces/total faeces ratio of 38 and 54 and 5 and 54% with respect to controls, at 0.5 and 1 mL/kg and 1 and 2 mg/kg, respectively) and bisacodyl-induced increase in large intestine transit in rats (125 and 280 and 210% with respect to controls, at 0.4 and 2 mL/kg Salicairine and 5 mg/kg loperamide, respectively). Salicairine was able to reduce contractions of isolated rat duodenum induced by barium chloride and acetylcholine, although not completely (that is about 60%) as seen with loperamide. Also, it did not change normal gastrointestinal transit in mice at doses of 0.5 to 1 mL/kg, conversely to loperamide which had a significant effect (decrease of 50%) at 2 mg/kg. Finally, Salicairine at 0.01 mL/mL, like loperamide at 0.2 mg/mL, significantly increased net fluid absorption in rat colon, either in basal conditions (30 and 64% respectively) or after a prostaglandin E1-induced increase in net fluid secretion (41 and 35%, respectively). The antidiarrheal activity of Salicairine is possibly related, at least in part, to an increase in colon net fluid absorption or a decrease in net fluid secretion.

DNA topoisomerase I inhibitors: cytotoxic flavones from Lethedon tannaensis.

From ethyl acetate and methanolic extracts of Lethedon tannaensis leaves, which were cytotoxic against murine leukemia (P-388) and human nasopharynx carcinoma (KB) cells, one new and six known 5-hydroxy-7-methoxyflavones variously substituted on the B ring were isolated and their structures determined by spectral analysis. Compounds active against KB cells were velutin (4) (IC50 4.8 microM), 7,3',5'-tri-O-methyltricetin (2) (IC50 22.2 microM), genkwanin (6) (IC50 30.6 microM), and the novel compound, 7,3',4'-tri-O-methyltricetin, named lethedocin (1) (IC50 47.6 microM). These flavones required the presence of hydroxyl groups at C-5 and C-4' and methoxyl groups at C-7 and C-3' for inhibition of calf thymus DNA topoisomerase I activity.

Cytotoxic cycloartanes from Aglaia argentea.

Aglaia argentea leaves yielded three new cycloartanes: argenteanones A and B, and argenteanol. The first two possess cytotoxic activity against KB cells (IC50 7.5 micrograms ml-1 and 6.5 micrograms ml-1 respectively). Structural elucidation was done by two-dimensional NMR spectroscopy.

An antimitotic and cytotoxic chalcone from Fissistigma lanuginosum.

Bioassay-guided fractionation of an ethyl acetate extract of Fissistigma lanuginosum led to the isolation of the known chalcone pedicin [1], which inhibited tubulin assembly into microtubules (IC50 value of 300 microM). From the same EtOAc fraction, two new condensed chalcones, fissistin [2] and isofissistin [3], which showed cytotoxicity against KB cells, were also obtained, together with the inactive dihydropedicin [4] and 6,7-dimethoxy-5,8-dihydroxyflavone [5]. In addition, the aminoquinones 6, 8, and 9 were isolated from the alkaloid extract. These compounds were artifacts, prepared by treatment of 1, 4, and 2, respectively, with NH4OH. The structures of the new compounds were elucidated by spectral methods, especially 2D nmr.

A preliminary chemotaxonomic review of Kopsia (Apocynaceae).

The present paper is the result of a botanical and chemical study of the Indo-Pacific genus Kopsia (Plumerioideae-Rauvolfieae) Apocynaceae. Some of the species of this genus possess medicinal uses. A survey of the accepted taxa and their synonymy, based on the study of types, is presented. Studies on alkaloids provides chemotaxonomic information. Indeed, in some cases, chemical relationships occur between species belonging to the same botanical group.

Flavonone and chalcone derivatives from Cryptocarya kurzii.

Four complex flavanones, kurziflavolactones A [2], B [3], C [4], and D [5] and a complex chalcone 6 with an unprecedented carbon side chain on the flavanone or chalcone A ring have been isolated from a Malaysian plant, Cryptocarya kurzii (Lauraceae). Their structures were determined by extensive spectroscopic analysis, especially 2D nmr experiments. Compounds 3 and 6 showed slight cytotoxicity against KB cells, with IC50 values of 4 and 15 micrograms/ml, respectively. A biosynthetic pathway for the formation of these compounds is suggested.

A novel leishmanicidal labdane from Polyalthia macropoda.

A new diterpene, (4S,9R,10R) methyl 18-carboxy-labda-8,13(E)-diene-15-oate has been obtained from the stem barks of Polyalthia macropoda (Annonaceae). This labdanic derivative was identified on the basis of spectroscopic data and is biologically active against the promastigote Leishmania donovani donovani.

Looking for new drugs: what criteria?

How to look for new drugs? What guidelines to use? Have we to continue investigations on plant and marine organisms? These questions arise frequently today. A pharmacological effect results from the addition of many effects at a molecular level, i.e. the interaction between a ligand and a receptor. As long as the chemical structure of this receptor remains unknown, studies of Nature's resources will yield the largest reservoir of new drugs. Nature provides our imagination with the pattern of novel biologically active molecules. Criteria classically used in the past to select plants for study were chemotaxonomy, ethnopharmacology or pharmacotaxonomy. Examples will be taken from personal experience, to illustrate work done according to the chemotaxonomical approach (Ochrosia and ellipticines), and the ethnopharmacological approach (antiinflammatory properties of Euphorbiaceae from New Caledonia). Taking into account that one of the major problems we have to face is the unsatisfactory classical pharmacological testing procedure, we have tried to set up a network grouping biologists and chemists. Among many results obtained, one concerns the use of the mammalian hypothalamo-pituitary system to screen effects of alkaloids extracted from Psychotria oleoides, a Rubiaceae collected in New Caledonia. Psycholeine exhibits an intriguing activity on GH release. Another result concerns the influence of a Labiatae extract on the adenylate cyclase system: 9 HODE extracted from Glechoma hederacea stimulates the basal level of enzyme activity in platelets, this activity being possibly involved in the folk uses claimed. Using the tubulin test to screen antimitotic activities of plant extracts, the biological activity of rhazinilam has been demonstrated as responsible for the antitubulin activity of a Malaysian plant, Kopsia singapurensis.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro cytotoxicity of polyindolenine alkaloids on rat hepatoma cell lines. Structure activity relationships.

New groups of polyindolenine alkaloids have been isolated from new species of the tribe Psychotriae (Rubiaceae). The cyto-inhibitory effects of these compounds on tumoral cell lines have been thoroughly investigated and thus allow the statement of relationships between some original structural patterns and the observed biological effects.

New Polyindolenine Alkaloids from Calycodendron milnei.

Four new alkaloids, representing the first members of new groups of polyindolinic alkaloids, have been isolated from the aerial parts of CALYCODENDRON MILNEI along with other alkaloids. The names vatine, its stereoisomer vatine A, vatamine, and vatamidine are proposed. They are polymers of six, seven, and eight N(b)-methyltryptamine units, respectively.

A new phytochemical survey of Malaysia. V. Preliminary screening and plant chemical studies.

A large phytochemical survey of the flora of the Malaysian Peninsula and Sabah is described, covering the systematic search for alkaloids, and partly, for saponins and flavonoids. Details of some chemical studies are reported. This emphasizes the great interest of such a study.