Pterocarpans and flavanones from Sophora flavescens displaying potent neuraminidase inhibition

Pterocarpans (1-3) and flavanones (4-10) were isolated from Sophora flavescens and screened for their ability to inhibit neuraminidase (an enzyme crucial in the proliferation of the influenza virus). The majority of inhibitors were shown to have IC(50) values of 20 microM or below. Interestingly, pterocarpan 1 emerged as the best inhibitor with an IC(50) of 1.4 microM. We were thus able to prove that the pterocarpan skeleton is a new class of lead structure for neuraminidase inhibitors. Our studies reveal that the IC(50) has a marked dependence upon structure in the case of the pterocarpans but much less so for the flavanones. Kinetic analysis disclosed that all inhibitors are noncompetitive. Our molecular docking experiment resulted that the most potent pterocarpan-derived inhibitor 1 may bind to another binding pocket adjacent to the active site.     

3-Keto steroids from the marine organisms Dendrophyllia cornigera and Cymodocea nodosa

The new (20R)-22E-cholesta-4,22-diene-3,6-dione (1), along with three known 3-keto steroids were isolated from the deep-water Mediterranean scleractinian coral Dendrophyllia cornigera (2-4). Moreover, four known related 3-keto steroids were isolated from the sea grass Cymodocea nodosa (5-8). The structure elucidation of steroid 1 and the full NMR resonance assignments of all isolated metabolites were based on interpretation of their spectral data. All compounds are reported for the first time as metabolites of the investigated organisms. Compounds 2 and 3 showed significant cytotoxicity against lung cancer NSCLC-N6 cell line.     

Leishmanicidal cycloartane-type triterpene glycosides from Astragalus oleifolius

Two new cycloartane-type glycosides oleifoliosides A (1) and B (2) were isolated from the lower stem parts of Astragalus oleifolius. Their structures were identified as 3-O-[beta-xylopyranosyl-(1 --> 2)-alpha-arabinopyranosyl]-6-O-beta-xylopyranosyl-3beta,6alpha,16beta,24(S),25-pentahydroxycycloartane and 3-O-[beta-xylopyranosyl-(1 --> 2)-alpha-arabinopyranosyl]-6-O-beta-glucopyranosyl-3beta,6alpha,16beta,24(S),25-pentahydroxycycloartane, respectively, by means of spectroscopic methods (IR, 1D and 2D NMR, ESI-MS). Three known cycloartane glycosides cyclocanthoside E (3), astragaloside II (4) and astragaloside IV (5) were also isolated and characterized. All five compounds were evaluated for in vitro trypanocidal, leishmanicidal and antiplasmodial activities as well as their cytotoxic potential on primary mammalian (L6) cells. Except for the compound 5, all compounds showed notable growth inhibitory activity against Leishmania donovani with IC50 values ranging from 13.2 to 21.3 microg/ml. Only weak activity against Trypanosoma brucei rhodesiense was observed with the known compounds astragaloside II (4, IC50 66.6 microg/ml) and cyclocanthoside E (3, IC50 85.2 microg/ml), while all compounds were inactive against Trypanosoma cruzi and Plasmodium falciparum. None of the compounds were toxic to mammalian cells (IC50's > 90 microg/ml). This is the first report of leishmanicidal and trypanocidal activity of cycloartane-type triterpene glycosides.     

Trypsin inhibitors from the garden four o'clock (Mirabilis jalapa) and spinach (Spinacia oleracea) seeds: isolation, characterization and chemical synthesis

Five serine proteinase inhibitors (Mirabilis jalapa trypsin inhibitors, MJTI I and II and Spinacia oleracea trypsin inhibitors, SOTI I, II, and III) from the garden four-o'clock (M. jalapa) and spinach (S. oleracea) seeds were isolated. The purification procedures included affinity chromatography on immobilized methylchymotrypsin in the presence of 5M NaCl, ion exchange chromatography and/or preparative electrophoresis, and finally RP-HPLC on a C-18 column. The inhibitors, crosslinked by three disulfide bridges, are built of 35 to 37 amino-acid residues. Their primary structures differ from those of known trypsin inhibitors, but showed significant similarity to the antimicrobial peptides isolated from the seeds of M. jalapa (MJ-AMP1, MJ-AMP2), Mesembryanthemum crystallinum (AMP1), and Phytolacca americana (AMP-2 and PAFP-S) and from the hemolymph of Acrocinus longimanus (Alo-1, 2 and 3). The association equilibrium constants (K(a)) with bovine beta-trypsin for the inhibitors from M. jalapa (MJTI I and II) and S. oleracea (SOTI I-III) were found to be about 10(7)M(-1). Fully active MJTI I and SOTI I were obtained by solid-phase peptide synthesis. The disulfide bridge pattern in both inhibitors (Cys1-Cys4, Cys2-Cys5 and Cys3-Cys6) was established after their digestion with thermolysin and proteinase K followed by the MALDI-TOF analysis.     

Further constituents from Caralluma negevensis

Two new megastigmane glycosides (1 and 2) and two new flavone glycosides (3 and 4) were isolated from the methanol extract of the whole plant of Caralluma negevensis Zohary (Asclepiadaceae). The structures of the isolated compounds were characterized as (9R)-2beta,9-dihydroxymegastigma-4,7-dien-3-one-9-O-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranoside (1), 2beta,9-dihydroxymegastigma-4-en-3-one 9-O-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranoside (2), luteolin 3'-O-beta-D-glucopyranoside-4'-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranoside (3), and luteolin 3',4'-di-O-beta-D-glucopyranoside (4). The structures of the isolated compounds were established on the basis of spectral evidence and chemical transformation.     

New polyoxygenated steroids from the Antarctic octocoral Dasystenella acanthina

The chemical study of the Antarctic octocoral Dasystenella acanthina has led to the isolation of the new polyoxygenated steroids (24R,22E)-24-hydroxycholest-4,22-dien-3-one (1), 23-acetoxy-24,25-epoxycholest-4-en-3-one (2), 12beta-acetoxycholest-4-en-3,24-dione (3), 12beta-acetoxy-24,25-epoxycholest-4-en-3-one (4), (22E)-25-hydroxy-24-norcholest-4,22-dien-3-one (5), 3alpha-acetoxy-25-hydroxycholest-4-en-6-one (6), and 3alpha,11alpha-diacetoxy-25-hydroxycholest-4-en-6-one (7), whose structures have been established by spectroscopic analysis. The absolute stereochemistry at C-24 in compound 1 has been determined through the 1H NMR study of the corresponding (R)- and (S)-MPA esters. All the new compounds showed significant activities as growth inhibitors of several human tumor cell lines. In addition, cytostatic and cytotoxic effects were also observed on selected tumor cell lines.     

Iridoids from Kigelia pinnata DC. fruits

From the fruits of Kigelia pinnata DC., a new furanone derivative formulated as 3-(2'-hydroxyethyl)-5-(2"-hydroxypropyl)-dihydrofuran-2(3H)-one (1), and four new iridoids named; 7-hydroxy viteoid II (2), 7-hydroxy eucommic acid (3), 7-hydroxy-10-deoxyeucommiol (4) and 10-deoxyeucommiol (5) have been isolated together with seven known iridoids, jiofuran (6), jioglutolide (7), 1-dehydroxy-3,4-dihydroaucubigenin (8), des-p-hydroxybenzoyl kisasagenol B (9), ajugol (10), verminoside (11) and 6-trans-caffeoyl ajugol (12). The structures of the isolated compounds were characterized by different spectroscopic methods.     

Inhibition of MMP-2 secretion from brain tumor cells suggests chemopreventive properties of a furanocoumarin glycoside and of chalcones isolated from the twigs of Dorstenia turbinata

A furanocoumarin glycoside new named turbinatocoumarin (1) was isolated from the twigs of Dorstenia turbinata. The structure of turbinatocoumarin (1) was assigned as 5-methoxy-3-[3-(beta-glucopyranosyloxy)-2-hydroxy-3-methylbutyl]psoralen by means of spectroscopic analysis. Known compounds have also been isolated from this genus and identified as (2'S, 3'R)-3'-hydroxymarmesin (2), 5-methoxy-3-(3-methyl-2,3-dihydroxybutyl)psoralen (3), psoralen (4), kanzonol C (5) which was isolated for the first time from this genus, 4-hydroxylonchocarpin (6), umbelliferone, 4-hydroxy-3-methoxybenzaldehyde and 4-methoxyphenol. As part of our continuing search for potential naturally-occurring antitumor drug candidates, the inhibition of matrix metalloproteinase (MMP)-2 secretion from brain tumor-derived glioblastoma cells by the isolated compounds 1, 3, 5, and 6 was evaluated by zymography and compared to the documented naturally-occurring MMP secretion inhibitors chlorogenic acid (CHL) and epigallocatechin-3-gallate (EGCg). Among the compounds tested, the inhibiting MMP secretion concentrations ranged from 0.025 to 250 microM with up to 80% inhibition. The inhibitory activities of compounds 5 and 6 were found comparable to the common reference compounds CHL and EGCg. This suggests that alternate sources can be explored and exploited for the availability of chemopreventive molecules.     

Xanthones with quinone reductase-inducing activity from the fruits of Garcinia mangostana (Mangosteen)

Bioactivity-guided fractionation of a dichloromethane-soluble extract of Garcinia mangostana fruits has led to the isolation and identification of five compounds, including two xanthones, 1,2-dihydro-1,8,10-trihydroxy-2-(2-hydroxypropan-2-yl)-9-(3-methylbut-2-enyl)furo[3,2-a]xanthen-11-one (1) and 6-deoxy-7-demethylmangostanin (2), along with three known compounds, 1,3,7-trihydroxy-2,8-di-(3-methylbut-2-enyl)xanthone (3), mangostanin (4), and alpha-mangostin (5). The structures of compounds 1 and 2 were determined from analysis of their spectroscopic data. All isolated compounds in the present study together with eleven other compounds previously isolated from the pericarp of mangosteen, were tested in an in vitro quinone reductase-induction assay using murine hepatoma cells (Hepa 1c1c7) and an in vitro hydroxyl radical antioxidant assay. Of these, compounds 1-4 induced quinone reductase (concentration to double enzyme induction, 0.68-2.2microg/mL) in Hepa 1c1c7 cells and gamma-mangostin (6) exhibited hydroxyl radical-scavenging activity (IC50, 0.20microg/mL).     

Inhibition of LPS-induced NO production by the oleogum resin of Commiphora wightii and its constituents

Three new (1-3) and five known compounds (4-8) were isolated from the oleogum resin of Commiphora wightii (Arnott.) Bhanol. Their structures were elucidated by spectroscopic and chemical methods. The MeOH extract and the EtOAc-sol. fraction were found to demonstrate significant inhibition of NO formation in lipopolysaccharide (LPS)-activated murine macrophages J774.1 in vitro (IC(50) values of 16.4 and 12.8 microg/ml, respectively). When compared with curcumin (IC(50) value of 12.3 microM), Z- and E-Guggulsterones (4 and 5, respectively) were the most potent inhibitors of NO production (IC(50) values of 1.1 and 3.3 microM, respectively), followed by myrrhanol A (7) and myrrhanone A (8) (IC(50) values of 21.1 and 42.3 microM, respectively). Guggulsterone-M (1) and its didehydro derivative (2) were weak inhibitors, while guggulsterols I (6) and Y (3) were inactive (IC(50) >500 microM).     

Triterpenoid saponins from Pteleopsis suberosa stem bark

Thirteen oleanane saponins (1-13), four of which were new compounds (1-4), were isolated from Pteleopsis suberosa Engl. et Diels stem bark (Combretaceae). Their structures were determined by 1D and 2D NMR spectroscopy and ESI-MS spectrometry. The compounds were identified as 2alpha,3beta,19alpha,23,24-pentahydroxy-11-oxo-olean-12-en-28-oic acid 28-O-beta-D-glucopyranosyl ester (1), 2alpha,3beta,19beta,23,24-pentahydroxy-11-oxo-olean-12-en-28-oic acid 28-O-beta-D-glucopyranosyl ester (2), 2alpha,3beta,19alpha,23-tetrahydroxy-11-oxo-olean-12-en-28-oic acid 28-O-beta-D-glucopyranosyl ester (3), and 2alpha,3beta,6beta,19alpha,24-pentahydroxy-11-oxo-olean-12- en-28-oic acid 28-O-beta-D-glucopyranosyl ester (4). The presence of alpha,beta-unsaturated carbonyl function was not common in the oleanane class and the aglycons of these compounds were not found previously in the literature. Moreover, the isolated compounds were tested against Helicobacter pylori standard and vacA, and cagA clinical virulence genotypes. Results showed that compound 6 has an anti-H. pylori activity against three metronidazole-resistant strains (Ci 1 cagA, Ci 2 vacA, and Ci 3).     

Characteristic of alkylated chalcones from Angelica keiskei on influenza virus neuraminidase inhibition

As part of our ongoing effort to develop influenza virus neuraminidase (NA) inhibitors from various medicinal plants, we utilized bioassay-guided fractionation to isolated six alkylated chalcones (1-6) from Angelica keiskei. Xanthokeistal A (1) emerged as new compound containing the rare alkyl substitution, 6,6-dimethoxy-3-methylhex-2-enyl. When we tested the ability of these individual alkyl substituted chalcones to inhibit influenza virus NA hydrolysis, we found that 2-hydroxy-3-methyl-3-butenyl alkyl (HMB) substituted chalcone (3, IC(50)=12.3 μM) showed most potent inhibitory activity. The order of potency of substituted alkyl groups on for NA inhibition was HMB>6-hydroxyl-3,7-dimethyl-octa-2,7-dienyl>dimethylallyl>geranyl. All NA inhibitors screened were found to be reversible noncompetitive inhibitors.     

Homoisoflavonoids from Ophiopogon japonicus Ker-Gawler

From the ethyl acetate extract of the tuberous roots of Ophiopogon japonicus (Liliaceae) eight known and five new homoisoflavonoidal compounds were isolated. The new compounds are 5,7-dihydroxy-8-methoxy-6-methyl-3-(2'-hydroxy-4'-methoxybenzyl)chroman-4-one (1), 7-hydroxy-5,8-dimethoxy-6-methyl-3-(2'-hydroxy-4'-methoxybenzyl)chroman-4-one (2), 5,7-dihydroxy-6,8-dimethyl-3-(4'-hydroxy-3'-methoxybenzyl)chroman-4-one (3), 2,5,7-trihydroxy-6,8-dimethyl-3-(3',4'-methylenedioxybenzyl)chroman-4-one (4) and 2,5,7-trihydroxy-6,8-dimethyl-3-(4'-methoxybenzyl)chroman-4-one (5). Their structures have been elucidated by mass and NMR spectroscopy. Compounds 4 and 5 are the first isolated homoisoflavonoids with a hemiacetal function at position 2.     

锐尖山香圆叶中三萜类成分的研究

从锐尖山香圆(Turpinia arguta (Lindl.) Seem.)叶中分离得到了11个三萜类化合物。通过光谱分析,分别鉴定其结构为熊果酸(1), 3β,6β,23-trihydroxy-12-oleanen-28-oic acid (2), 3β,6β,23-trihydroxyurs-12-en-28-oic acid (3), 3β,6β,19α,23-tetrahydroxyurs-12-en-28-oic acid (4), 1 α, 3β,23-trihydroxy-12-oleanen-28-oic acid (5), arjunglucoside II (6), rosamultin (7), 3β-O-β-D-glucopyranoylcincholic acid (8), cinchonaglycoside C (9), mussaendoside S (10) 和3β-O-β-D-glucopyranosyl quinovic acid 28-O-β-D-glucopyranosyl ester (11)。除化合物1和6,其它化合物均为首次从山香圆叶中分离得到。     

Insect antifeedants, pterocarpans and pterocarpol, in heartwood of Pterocarpus macrocarpus Kruz

The insect antifeedant activities of pterocarpans and a sesquiterpene alcohol from the dichloromethane extract of Pterocarpus macrocarpus Kruz. (Leguminosae) were evaluated against the common cutworm, Spodoptera litura F. (Noctuidae), and the subterranean termite, Reticulitermes speratus (Kolbe)(Rhinotermitidae). Three pterocarpans, (-)-homopterocarpin (1), (-)-pterocarpin (2), and (-)-hydroxyhomopterocarpin (3) and the sesquiterpene alcohol, (+)-pterocarpol (5), were isolated from the dichloromethane extract of the heartwood of P. macrocarpus under guidance by a biological assay. Among these natural products, the most active insect antifeedant against both S. litura and R. speratus was 1. On the other hand, sesquiterpene alcohol 5 showed less insect antifeedant activity than the other pterocarpans against both insect species. While its methylated derivative, (-)-methoxyhomopterocarpin (4), showed high biological activity, 3 showed less insect antifeedant activity in this study. Interestingly, racemic 1 did not show insect antifeedant activity against S. litura. However, all of the test pterocarpans and isoflavones showed antifeedant activity against the test termites. Additionally, since these compounds were major constituents of P. macrocarpus, these antifeedant phenolics may act as chemical defense factors in this tree. In Thailand, lumber made from this tree is used to make furniture and in building construction due to its resistance to termite attack.     

Studies on the late steps of (+) pisatin biosynthesis: evidence for (-) enantiomeric intermediates

Pisatin, a 6a-hydroxyl-pterocarpan phytoalexin from pea (Pisum sativum L.), is relatively unique among naturally occurring pterocarpans by virtue of the (+) stereochemistry of its 6a-11a C-C bond. However, pisatin synthesizing pea tissue has an isoflavone reductase, first identified in alfalfa, which acts on the (-) antipode. In order to establish the natural biosynthetic pathway to (+) pisatin, and to evaluate the possible involvement of intermediates with a (-) chirality in its biosynthesis, we administered chiral, tritium-labeled, isoflavanones and pterocarpans to pisatin-synthesizing pea cotyledons and compared the efficiency of their incorporation. Pea incorporated the isoflavanone, (-) sophorol, more efficiently than either its (+) antipode, or the pterocarpans (+) or (-) maackiain. (-) Sophorol was also metabolized by protein extracts from pisatin-synthesizing pea seedlings in a NADPH-dependent manner. Three products were produced. One was the isoflavene (7,2'-dihydroxy-4',5'-methylenedioxyisoflav-3-ene), and another had properties consistent with the isoflavanol (7,2'-dihydroxy-4',5'-methylenedioxyisoflavanol), the expected product for an isoflavanone reductase. A cDNA encoding sophorol reductase was also isolated from a cDNA library made from pisatin-synthesizing pea. The cloned recombinant sophorol reductase preferred (-) sophorol over (+) sophorol as a substrate and produced 7,2'-dihydroxy-4',5'-methylenedioxyisoflavanol. Although no other intermediates in (+) pisatin biosynthesis were identified, the results lend additional support to the involvement of intermediates of (-) chirality in (+) pisatin synthesis.     

鞭打绣球中的一个新单萜苷

从鞭打绣球(Hemiphragma heterophyllum Wall.)全草中分离到1个新单萜苷和7个已知化合物.通过波谱数据分析,新单萜苷的结构鉴定为(4S)-α-萜烯醇-8-O-β-D-比喃木糖-(1→6)-β-D-比喃葡萄糖苷,已知化合物分别鉴定为globularin(2)、(2S 3S,4R,9E)-1,3,4-trihydroxy-2-[(2'R)-hydroxy-tetracosanoylamino]-9-octadecene(3)、β-香树素(4)、齐墩果酸(5)、肉桂酸(6)、β-谷甾醇(7)和胡萝卜甙(8).除化合物2外,其余化合物均为首次从鞭打绣球中分离得到.     

Flavonols and an oxychromonol from Piliostigma reticulatum

The leaf extract from the plant Piliostigma reticulatum was found to exhibit antimicrobial activity against some bacteria and fungi such as Staphylococcus aureus (NCTC 6571), Escherichia coli (NCTC 10418), Bacillus subtilis (NCTC 8236), Proteus vulgaris (NCTC 4175), Aspergillus niger (ATCC 10578) and Candida albicans (ATCC 10231). Upon investigation of the chemical constituents present in the leaf extract, a total of seven compounds were isolated and their structures were unambiguously established by spectroscopic methods including HR-MS and NMR spectrometry. Four of the isolated compounds were novel, namely 6-C-methyl-2-p-hydroxyphenyloxychromonol (piliostigmol), 1, 6,8-di-C-methylquercetin-3,3',7-trimethyl ether, 2, 6,8-di-C-methylquercetin-3,3'-dimethyl ether, 3 and 3',6,8,-tri-C-methylquercetin-3,7-dimethyl ether, 4. The other three were known C-methylated flavonols and they were isolated from P. reticulatum for the first time. These were 6-C-methylquercetin-3-methyl ether, 5, 6,8-di-C-methylkaempferol-3-methyl ether, 6 and 6-C-methylquercetin-3,3',7-trimethyl ether 7. All the isolated compounds were tested for cytotoxicity using the brine shrimp toxicity assay and all of them were active albeit at different levels. With respect to antibacterial activity piliostigmol, 1 showed the highest activity against E. coli (MIC=2.57 microg/ml, 0.006 micromol), which is three times more that of Amoxicillin, where as 4 and 7 showed the least activity.     

Plocoralides A-C, polyhalogenated monoterpenes from the marine alga Plocamium corallorhiza

Three new polyhalogenated monoterpenes, plocoralides A-C (1-3) along with three known compounds (4-6) have been isolated from the organic extract of the red alga P. corallorhiza. Structures of the new compounds were characterized as 4,8-dibromo-1,1-dichloro-3,7-dimethyl-2E,6E-octadiene (1), 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2E,7-octadiene (2) and 4,8-dibromo-1,1,7-trichloro-3,7-dimethyl-2E,5Z-octadiene (3) on the basis of one- and two-dimensional NMR spectroscopic data and MS analyses. Compounds 2-6 show moderate cytotoxicity toward esophageal cancer cells.     

Cytotoxic lupane-type triterpenoids from Acacia mellifera

One new and eight previously described lupane-type metabolites were isolated for the first time from Acacia mellifera (Leguminosae). Based on spectral analyses, the structure of the new compound was elucidated as 28-hydroxy-3-oxo-lup-20-(29)-en-30-al (1), while the known compounds were identified as 3-oxo-lup-20-(29)-en-30-al (2), 3-hydroxy-lup-20-(29)-en-30-al (3), 28-hydroxy-lup-20-(29)-en-3-one (4), lupenone (5), lupeol (6), betulin (7), betulinic acid (8), and betulonic acid (9). Metabolites 2, 3, and 4 are reported for the first time in the Leguminosae family. The cytotoxicity of the isolated metabolites was evaluated on the NSCLC-N6 cell line, derived from a human non-small-cell bronchopulmonary carcinoma. Compounds 1 and 3 exhibited significant levels of activity.