Smokeless tobacco-induced lamellar body abnormalities.

OBJECTIVES: To compare the morphological changes and quantitative distribution of lamellar bodies (Lb) (membrane coating granules) in the hamster cheek pouch epithelium with smokeless tobacco (ST). MATERIALS AND METHODS: Archives of experimental material from previously published studies [S. Ashrafi, A. Das, R. Worawongvasu, B. Mehdinejad and J. Waterhouse (1992) Scanning Microscopy6: 183] were utilized. Animals in experimental group received most ST (snuff) in their right pouch, 5 days weekly, for 24 months, while no snuff was given to control group. After 24 months, the epithelial tissues were processed for electron microscopic study. Volume densities of Lb were assessed by morphometry. MAIN OUTCOME MEASURES: Densities of Lb in the two groups, experimental vs control. RESULTS: In the control, Lb extruded their contents into the intercellular spaces of upper granular layers and in between the last granular cell layers and keratin layers to form a permeability barrier. Conversely, in the smokeless tobacco-treated epithelium, the majority of the Lb that were formed remained inside and accumulated within the granular cells, without extruding their contents into the intercellular spaces to form a lipid compound permeability barrier. CONCLUSIONS: Commercial alkaline ST may have contributed to the abnormal accumulation of Lb in the granular cell layer and affected the extrusion process of Lb to form an incomplete permeability barrier in the oral epithelium.

Prediction of human absorption of natural compounds by the non-everted rat intestinal sac model.

A major concern in natural drug research is that many substances with potent biological activity in vitro are unable to generate good activity in vivo owing to their poor water-solubility, poor permeability and/or poor stability. The permeability of drug candidates across the intestinal mucosa is one of the most important factors in defining drug bioavailability and biological activity. In order to screen promising compounds for further investigation, a non-everted rat intestinal sac model has been developed successfully to assay the permeability of natural compounds and to predict their human absorption. In this system, the drug solution was placed in non-everted intestinal sacs (NEIS), which were placed in an acceptor solution and the permeability of drug across intestine walls was determined. The feasibility of this method has been validated and demonstrated for 11 model compounds chosen from currently marketed drugs whose human fraction absorbed (Fa) data have been reported. The results of the studies indicate that a good relationship exists between the permeability of the model drugs and their corresponding Fa data. The permeability of 13 natural compounds was evaluated using this system. Only fraxinellone and vitexin-7-glucoside exhibited high intestinal permeability, and predictive of excellent human absorption, which awaits confirmation from further investigation in vivo. This model provides an alternative method to everted intestinal sacs for the evaluation of in vitro permeability in rats, and for estimating human absorption of drugs. It may therefore hold great promise for oral absorption screening of new drug candidates.

Synthesis of new artemisinin analogues from artemisinic acid modified at C-3 and C-13 and their antimalarial activity.

Artemisinic acid (2) was modified through allylic oxidation at C-3 or conjugate addition at C-13 to afford 12 methyl artemisinate derivatives (4-15). Photooxidation of the derivatives yielded eight new artemisinin analogues, including 13-cyanoartemisinin (16), 13-methoxycarbonyl artemisinin (17), 13-methoxyartemisinin (18), 13-ethylsulfonylartemisinin (19), 13-nitromethylartemisinin (20), 13-(1-nitroethyl)artemisinin (21), (3R)-3-hydroxyartemisinin (22), and (3R)-3-acetoxyartemisinin (23). Among the analogues, only compound 20 had antimalarial activity comparable to artemisinin (1).

Cytotoxic polyacetylenes from the twigs of Ochanostachys amentacea.

Bioassay-guided investigation of the twigs of Ochanostachys amentacea using LNCaP (hormone-dependent human prostate cancer) cells as a monitor led to the isolation of three alkynes, the known (S)-17-hydroxy-9,11,13,15-octadecatetraynoic acid (minquartynoic acid, 1) and two novel analogues, (S)-17,18-dihydroxy-9,11,13,15-octadecatetraynoic acid (2) and (S)-17-hydroxy-15E-octadecen-9,11,13-triynoic acid (3). Compounds 1-3 were tested against a panel of human tumor cell lines and found to be significantly cytotoxic.

The potential of alkaloids in drug discovery.

Alkaloids are an important group of diversely distributed, chemically, biologically and commercially significant natural products. This article suggests why now, with the presently available technology, and the remaining biome available and reasonably accessible, is an opportune moment to consciously focus on the discovery of further alkaloids with pharmacophoric utility.

Alkyl phenols and derivatives from Tapirira obtusa.

From the bark of Tapiria obtusa, six alkyl phenol derivatives were isolated: 1-hydroxy-3-[(Z)-7'-nonadecenyl]-benzene, 1-hydroxy-3-[(Z)-7'-heptadecenyl]-benzene, 1-hydroxy-3-[14'-phenyltetradecyl]-benzene, and 1-hydroxy-3-[16'-phenyltetradecyl]-benzene, and their possible biogenetic precursors, 1-(16'-phenyl-12'Z-hexadecenyl)-4-Z-cyclohexene-(1S*,3S*)-diol and (4S*,6S*)-dihydroxy-6-(14'Z-nonadecenyl)-2-cyclohexenone. The structures of these compounds were elucidated by chemical and spectroscopic analysis, (4S*,6S*)-Dihydroxy-6-(14'Z-nonadecenyl)-2-cyclohexenone showed cytotoxic activity.

Constituents of Afzelia bella stem bark.

The stembark of Afzelia bella yielded an acylated dihydroflavonol glycoside identified as 2R,3R-trans-aromadendrin-7-O-beta-D-glucopyranoside-6''-(4''-hydroxy-2''-methylene butanoate), along with five known flavonoids and the lignan glycoside (+)-isolariciresinol 9-O-xyloside. Their structures were determined by detailed 1D and 2D NMR analyses.

Modulation of the multidrug-resistance phenotype by new tropane alkaloid aromatic esters from Erythroxylum pervillei.

Nine tropane alkaloid aromatic esters (1-9) were isolated from the roots of Erythroxylum pervillei by following their potential to reverse multidrug-resistance with vinblastine-resistant oral epidermoid carcinoma (KB-V1) cells. All isolates, including seven new structures (3-9), were evaluated against a panel of human cancer cell lines, and it was found that alkaloids 3 and 5-9 showed the greatest activity with KB-V1 cells assessed in the presence of vinblastine, suggesting that these new compounds are potent modulators of P-glycoprotein. Confirmatory results were obtained with human ovarian adenocarcinoma (SKVLB) cells evaluated in the presence of adriamycin and synergistic studies performed with several cell lines from the NCI tumor panel. The structures of the new compounds were determined using spectroscopic techniques. Single-crystal X-ray analysis was performed on the monoester, tropane-3 alpha,6 beta,7 beta-triol 3-phenylacetate (1).

Biodiversity and drug discovery--a symbiotic relationship.

The profound developments in natural products drug discovery in the past few years are discussed, and the importance of a global approach to biodiversity and drug discovery involving natural products for the early part of the 21st century is presented.

Triterpene glycosides from Cimicifuga racemosa.

Eight new triterpene glycosides named cimiracemosides A-H, respectively, and eight known triterpene glycosides were isolated from the rhizome extracts of black cohosh (Cimicifuga racemosa). The new compounds were determined by spectral data to be 21-hydroxycimigenol-3-O-alpha-L-arabinopyranoside (1), 21-hydroxycimigenol-3-O-beta-D-xylopyranoside (2), cimigenol-3-O-alpha-L-arabinopyranoside (3), 12beta-acetoxycimigenol-3-O-alpha-L-arabinopyranoside (4), 24-acetylisodahurinol-3-O-beta-D-xylopyranoside (5), 20(S),22(R), 23(S),24(R)-16beta:23;22:25-diepoxy-12beta-acetoxy-3be ta,23, 24-trihydroxy-9,19-cycloanost-7-ene-3-O-beta-D-xylopyranoside (6), 20(S),22(R),23(S),24(R)-16beta:23;22:25-diepoxy-12beta -acetoxy-3beta, 23,24-trihydroxy-9,19-cycloanost-7-en-3-O-alpha-L-arabinopyrano side (7), and 20(S),22(R),23(S), 24(R)-16beta:23;22:25-diepoxy-12beta-acetoxy-3beta,23, 24-trihydroxy-9,19-cycloanostane-3-O-beta-D-xylopyranoside (8).

A cytotoxic diterpene from Alomia myriadenia.

An extract of the aerial parts from Alomia myriadenia Schultz-Bip. ex Baker (Asteraceae) showed significant cytotoxicity against a panel of human cancer cell lines in a screening of extracts from Brazilian Atlantic Forest plant species. Employing a bioassay-linked HPLC-electrospray/MS method, followed by semi-preparative HPLC, the active component was isolated and characterized as a mixture of epimers of the labdane diterpene 12S,16-dihydroxy-ent-labda-7,13-dien-15,16-olide.

Liquid chromatography-electrospray ionization mass spectrometry study of the flavonoids of the roots of Astragalus mongholicus and A. membranaceus.

High-performance liquid chromatography-electrospray ionization mass spectrometry has been applied to analyze the flavonoids of Huangqi, the roots of Astragalus mongholicus and A. membranaceus. Eight flavonoids were identified as calycosin-7-O-beta-D-glucoside, calycosin-7-O-beta-D-glucoside-6"-O-malonate (2), ononin, (6aR,11aR)-3-hydroxy-9,10-dimethoxypterocarpan-3-O-bet a-D-glucoside, calycosin, (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavan-7-O-beta-D-glucoside, formononetin-7-O-beta-D-glucoside-6"-O-malonate and formononetin by direct comparison with the isolated standards from Huangqi. The existence of (6aR,11aR)-3-hydroxy-9,10-dimethoxypterocarpan, (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavan, astrapterocarpanglucoside-6'-O-malonate and astraisoflavanglucoside-6'-O-malonate was detected. This is the first report of flavonoid glycoside malonates in these two Astragalus species, and malonate 2 is a structurally completely identified new compound.

5-(4-Hydroxyphenethenyl)-4,7-dimethoxycoumarin, a new constituent of Monotes engleri.

A new coumarin, 5-(4-hydroxyphenethenyl)-4,7-dimethoxycoumarin (1) was isolated from the combined ethyl acetate extracts of the root bark, root wood and stem bark of Monotes engleri, and found to be cytotoxic against two cell lines in a human tumor panel. Its structure was determined on the basis of spectroscopic methods.

Cytotoxic constituents of the roots of Ekmanianthe longiflora.

Bioactivity-directed fractionation of the CHCl(3) extract of the roots of Ekmanianthe longiflora resulted in the isolation of three new natural products, (2R,3R,4R)-3,4-dihydro-3, 4-dihydroxy-2-(3-methyl-2-butenyl)-1(2H)-naphthalenone (1), (2S,3R, 4R)-3,4-dihydro-3, 4-dihydroxy-2-(3-methyl-2-butenyl)-1(2H)-naphthalenone (2), and (2R, 3aR,9R,9aR)-9-hydroxy-2-(1-hydroxy-1-methylethyl)-2,3,3a,4,9 , 9a-hexahydro-naphtho[2,3-b]furan-4-one (3), together with the known compounds 2-(1-hydroxyethyl)naphtho[2,3-b]furan-4,9-quinone (4), 2-acetylnaphtho[2,3-b]furan-4,9-quinone (5), dehydro-iso-alpha-lapachone (6), alpha-lapachone (7), catalponol, and epi-catalponol. The structures of 1-3 were determined using a combination of NMR spectroscopic techniques, and the absolute configurations of compounds 1 and 2 were obtained using Mosher ester methodology. Compounds 4-6 showed significant cytotoxicity in a panel of human cancer cells. alpha-Lapachone (7) exhibited only marginal activity, and catalponol and epi-catalponol were inactive in this regard. When tested at 72 mg/kg/injection in an in vivo mouse P-388 leukemia system, compound 4 was inactive (110% T/C).

LC-ESI-MS study of the flavonoid glycoside malonates of red clover (Trifolium pratense).

High-performance liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) was applied to the analysis of the flavonoids and their glycoside malonates of the flowers and leaves of red clover (Trifolium pratense). Through LC-MS comparative studies on the plant extracts and their malonate-free extracts, approximately 20 flavonoid glycoside malonates were detected in the flower extract. Eight were identified as genistin 6' '-O-malonate (39), formononetin 7-O-beta-D-glucoside 6' '-O-malonate (40), biochanin A 7-O-beta-D-glucoside 6' '-O-malonate (41), trifoside 6' '-O-malonate (42), irilone 4'-O-beta-D-glucoside 6' '-O-malonate (43), pratensein 7-O-beta-D-glucoside 6' '-O-malonate (44), isoquercitrin 6' '-O-malonate (45), and 3-methylquercetin 7-O-beta-D-glucoside 6' '-O-malonate (46). About 15 other flavonoids and clovamides were proved to be present in this extract. The study also found that the flowers contained flavones as the major flavonoids, whereas the leaves had isoflavones as the major flavonoids. This is the first detection of the six malonates (39 and 42-46) in the extracts of red clover, and among them, 42, 43, and 46 are new compounds.

Constituents of zanthoxylum sprucei.

The known compounds lupeol, ß-sitosterol, (+)-sesamin, trans -dimethylmatairesinol, hesperidin, (-)- cis - N -methylcanadine and sucrose were isolated from Zanthoxylum sprucei . The 1 H-NMR and 13 C-NMR signals of (-)- cis - N -methylcanadine are hereby fully assigned.

Gallic Acid derivatives from mezoneuron benthamianum leaves.

The leaves of Mezoneuron benthamianum yielded methyl gallate and gallic acid as the constituents responsible for its antibacterial activity. (-)-Shikimic acid-3-O-gallate, 1-O-methyl-D-chiro-inositol, (-)-epicatechin, (-)-epicatechin-3-gallate and kaempferol-3- (6?-galloyl) glucoside were also isolated. The minimum inhibitory concentrations of these compounds against some Gram-positive and Gram-negative microorganisms and a fungus are presented.

O- and N-methylation in the biosynthesis of staurosporine.

The feeding of (13)C- and (2)H-enriched methionine to Streptomyces staurosporeus established that the methyl carbon and proton source of both the 3'-O- and 4'-N-methyl groups of staurosporine (1) was methionine and that all three methyl protons from methionine were retained on 1. In the presence of the methyltransferase inhibitor, sinefungin, the biosynthesis of staurosporine was blocked at the last step, O-methylation. An intermediate, 3'-demethoxy-3'-hydroxystaurosporine (2), was efficiently accumulated in the medium. Other general methyltransferase inhibitors failed to produce any other staurosporine intermediates or analogues.

Cytotoxic sesquiterpenoids from Ratibida columnifera.

Bioassay-directed fractionation of the flowers and leaves of Ratibida columnifera using a hormone-dependent human prostate (LNCaP) cancer cell line led to the isolation of 10 cytotoxic substances, composed of five novel xanthanolide derivatives (2-4, 7, and 8), a novel nerolidol derivative (9), and three known sesquiterpene lactones, 9alpha-hydroxy-seco-ratiferolide-5alpha-O-angelate+ ++ (1), 9alpha-hydroxy-seco-ratiferolide-5alpha-O-(2-methylbut yrate) (5), 9-oxo-seco-ratiferolide-5alpha-O-(2-methylbutyrate) (6), as well as a known flavonoid, hispidulin (10). On the basis of its cytotoxicity profile, compound 5 was selected for further biological evaluation, and was found to induce G1 arrest and slow S traverse time in parental wild type p53 A2780S cells, but only G2/M arrest in p53 mutant A2780R cells, with strong apoptosis shown for both cell lines. The activity of 5 was not mediated by the multidrug resistance (MDR) pump, and it was not active against several anticancer molecular targets (i.e., tubulin polymerization/depolymerization, topoisomerases, and DNA intercalation). While these results indicate that compound 5 acts as a cytotoxic agent via a novel mechanism, this substance was inactive in in vivo evaluations using the murine lung carcinoma (M109) and human colon carcinoma (HCT116) models.

1',2',3',4'-tetradehydrotubulosine, a cytotoxic alkaloid from Pogonopus speciosus.

Bioassay-guided phytochemical investigation of the stems of Pogonopus speciosus, using human oral epidermoid carcinoma (KB) cells as a monitor, led to the isolation of a novel alkaloid, 1',2', 3',4'-tetradehydrotubulosine (1), along with tubulosine (2) and psychotrine (3) as bioactive constituents. The structure of the novel compound was elucidated through 1D- and 2D-NMR spectroscopic methods. Alkaloids 1 and 3 showed weak cytotoxic activity against a panel of human cancer cell lines, with the potency of these compounds being markedly less than that of tubulosine (2).