Isolation and structure identification of an active DNA strand-scission agent, (+)-3,4-di-hydroxy-8,9-methylenedioxypterocarpan

Synthesis and antiproliferative activity of 6-naphthylpterocarpans

The Heck-oxyarylation of racemic 2-(1-naphthyl)- and 2-(2-naphthyl)-2H-chromene derivatives were carried out resulting diastereoselectively in (6S*,6aR*,11aR*)-6-(1-naphthyl)- and 6-(2-naphthyl)-pterocarpans as major products and bridged (6R*,12R*)-6,12-methanodibenzo[d,g][1,3]dioxocine derivatives as minor products. Antiproliferative activity of two 6-naphthylpterocarpans was identified by MTT assay against A2780 and WM35 human cancer cell lines with low micromolar IC50 values. The measured 0.80 and 3.51 μM IC50 values of the (6S*,6aR*,11aR*)-6-(1-naphthyl)pterocarpan derivative with 8,9-methylenedioxy substitution represent the best activities in the pterocarpan family. Enantiomers of the pterocarpan and dioxocine derivatives and their chiral 2-naphthylchroman-4-one and 2-naphthyl-2H-chromene precursors were separated by HPLC using chiral stationary phase. HPLC-ECD spectra were recorded and absolute configuration and low-energy solution conformations were determined by TDDFT-ECD calculations. Characteristic ECD transitions of the separated enantiomers were correlated with their absolute configuration.

Three new pterocarpans from the aerial parts of Abrus Precatorius

Three new pterocarpans, named abrusprecatins A-C (1-3), along with three known ones, namely medicarpin (4), maackiain (5), and 4-hydroxy-3-methoxy-8,9-methylenedioxypterocarpan (6) were isolated from the aerial parts of Abrus precatorius. The structures of these compounds were established by extensive analysis of mass spectrometric data, 1 D and 2 D NMR spectroscopic data. In addition, the absolute configurations were determined by a combination of single crystal X-ray diffraction analysis and circular dichroism spectroscopy.

Diverse flavonoids from the roots of Millettia brandisiana

The phytochemical investigation for the constituents of the roots of Millettia brandisiana, using bioassay guided fractionation, resulted in the isolation of five previously undescribed (namely brandisianones A-E) and twenty-six known flavonoids. Their chemical structures were determined using a combination of NMR, MS, IR, optical rotation and CD analysis, as well as comparison with the literature data. The crude extract as well as the isolated compounds were evaluated in various biological assays for their cytotoxicity against a panel of human cancer cell lines, potential inhibitory activity against aromatase, and antioxidant property using the oxygen radical absorbance capacity (ORAC) with an aim to search for leads and develop them to drug candidates in our drug discovery effort, we identified three bioactive flavonoids from M. brandisiana which could be further developed into a potential chemopreventive (antiaromatase) agent against breast cancer.

Cicadamides A and B,N-Acetyldopamine Dimers From the InsectPeriostracum cicadae

Two new N-acetyldopamine dimers, cicadamides A (1) and B (2), and 8 known compounds were isolated from the medicinal insect Periostracum cicadae. Their structures including absolute configurations were assigned by spectroscopic and computational methods. Biological activities of compounds 1, (+)-2, and (–)-2 toward human cancer cells BGC-823, HepG2, and A549 were evaluated.

Phenolic Metabolites of Dalea ornata Affect Both Survival and Motility of the Human Pathogenic Hookworm Ancylostoma ceylanicum

Hookworms are ubiquitous human parasites, infecting nearly one billion people worldwide, and are the leading cause of anemia and malnutrition in resource-limited countries. Current drug treatments rely on the benzimidazole derivatives albendazole and mebendazole, but there is emerging resistance to these drugs. As part of a larger screening effort, using a hamster-based ex vivo assay, anthelmintic activity toward Ancylostoma ceylanicum was observed in the crude extract of aerial parts of Dalea ornata. These studies have led to the isolation and characterization of phenolic metabolites 1-10. The structures were determined by 1D and 2D NMR spectroscopy, and the absolute configuration of 1 was assigned using electronic circular dichroism data. The new compound, (2S)-8-(3-methylbut-2-en-1-yl)-6,7,4'-trihydroxyflavanone (1), was weakly active at 7.3 μM, with 17% reduction in survival of the hookworms after 5 days. The rotenoids deguelin (9) and tephrosin (10), predictably perhaps, were the most active, with complete worm mortality observed by day 4 (or earlier) at 6.3 and 6.0 μM, respectively. The effects of 1-10 on hookworm motility and on toxicity to hamster splenocytes were also explored as important measures of treatment potential.

Understanding cancer and the anticancer activities of naphthoquinones – a review

Naphthoquinone moieties are present in drugs such as doxorubicin which are used clinically to treat solid cancers.

Activity of three cytotoxic isoflavonoids from Erythrina excelsa and Erythrina senegalensis (neobavaisoflavone, sigmoidin H and isoneorautenol) toward multi-factorial drug resistant cancer cells

INTRODUCTION

Resistance of cancer cells to chemotherapy has become a worldwide concern. Naturally occuring isoflavonoids possess a variety of biological activities including anti-cancer effects. The present study was aimed at investigating the cytotoxicity and the modes of action of three naturally occuring isoflavonoids, neobavaisoflavone (1), sigmoidin H (2) and a pterocarpan that is a special type of isoflavonoid, isoneorautenol (3) against a panel of nine cancer cell lines, including various sensitive and drug-resistant phenotypes.

METHODS

The cytotoxicity of the compounds was determined using a resazurin reduction assay, whereas the caspase-Glo assay was used to detect the activation of caspases 3/7, caspase 8 and caspase 9 in cells treated with compounds 3. Flow cytometry was used for cell cycle analysis and detection of apoptotic cells, analysis of mitochondrial membrane potential (MMP) as well as measurement of reactive oxygen species (ROS).

RESULTS

Compounds 3 showed significant cytotoxicity toward sensitive and drug-resistant cancer cell lines. Compounds 1 and 2 were selectively active, and IC50 values below 115 μM were obtained on 6/9 and 4/9 cell lines respectively with values ranging from 42.93 μM (toward CCRF-CEM cells) to 114.64 μM [against HCT116 (p53(+/+)) cells] for 1 and 25.59 μM (toward U87MG) to 110.51 μM [against HCT116 (p53(+/+)) cells] for 2. IC50 values ranging from 2.67 μM (against MDA-MB 237BCRP cells) to 21.84 (toward U87MG) were measured for compound 3 and between 0.20 μM (toward CCRF-CEM cells) and 195.12 μM (toward CEM/ADR5000 cells) for doxorubicin as control drug. BCRP-transfected MDA-MB-231 cells, HCT116 (p53(+/+)) and U87MG.ΔEGFR cells were hypersensitive (collateral sensitive) to compound 3 as compared to their counterpart cell lines. Compound 3 induced apoptosis in CCRF-CEM cells via activation of caspases 3/7, 8 and 9 as well as the loss of MMP and increased ROS production.

CONCLUSIONS

The cytotoxicity of the studied isoflavonoids and especially the pterocarpan 3 deserve more detailed exploration in the future to develop novel anticancer drugs against sensitive and otherwise drug-resistant phenotypes.

The chemical constituents of the twigs of Ammopiptanthus nanus

Two new isoflavone glycosides, ammopiptanosides A and B, have been isolated from the 95% EtOH extract of the twigs of Ammopiptanthus nanus (M.Pop.) Cheng f., together with six known compounds, and their structures were characterized by spectroscopic methods and compared with the data in the literature.

Kazinol Q from Broussonetia kazinoki enhances cell death induced by Cu(II) through increased reactive oxygen species

The ability of the flavan kazinol Q (KQ) to induce DNA breakage in the presence of Cu(II) was examined by agarose gel electrophoresis using supercoiled plasmid DNA. In KQ-mediated DNA breakage reaction, the involvement of reactive oxygen species (ROS), H₂O₂ and O₂^- was established by the inhibition of DNA breakage by catalase and revealed DNA breakage by superoxide dismutase (SOD). The cell viability of gastric carcinoma SCM-1 cells treated with various concentrations of KQ was significantly decreased by cotreatment with Cu(II). Treatment of SCM-1 cells with 300 μM Cu(II) enhanced the necrosis induced by 100 μM KQ. Treatment of SCM-1 cells with 100 μM KQ in the presence of 300 μM Cu(II) increased the generation of H₂O₂. Taken together, the above finding suggested that KQ cotreatment with Cu(II) produced increased amounts of H₂O₂, thus enhancing subsequent cell death due to necrosis.

Synthesis of Pterocarpans

The total synthesis of natural pterocarpans and analogs is reviewed.

Anti-inflammatory and enzyme inhibitory activities of a crude extract and a pterocarpan isolated from the aerial parts of Vitex agnus-castus

A new compound, 6a,11a-dihydro-6H-[1] benzofuro [3,2-c][1,3]dioxolo[4,5-g]chromen-9-ol was isolated from the ethyl acetate fraction of Vitex agnus-castus. The structure of this compound was identified with the help of spectroscopic techniques ((13)C NMR, (1)H NMR, HMBC, HMQC, NOESY and COSY). The compound showed low urease- (32.0%) and chymotrypsin- (31.4%) inhibitory activity, and moderate (41.3%) anti-inflammatory activity. The crude extract and various fractions obtained from the aerial parts of the plant were also screened for possible in vitro hemagglutination, antibacterial and phytotoxic activities. No hemagglutination activity against human erythrocytes was observed in crude extracts and fractions of V. agnus-castus. The fractions and crude methanolic extract showed moderate and low antibacterial activity. Exceptions were the CHCl(3) fraction, which showed significant antibacterial activity against Klebsiella pneumonia (81% with MIC(50)=2.19 mg/mL), the n-hexane fraction, which exhibited no activity against Salmonella typhi, and the CHCl(3) and aqueous fractions, which showed no activity against Bacillus pumalis. Moderate phytotoxic activity (62.5%) was observed by n-hexane fraction of V. agnus-castus against Lemna minor L at 1000 μg/mL.

Pterocarpenes elicited by Aspergillus caelatus in peanut (Arachis hypogaea) seeds

The substituted pterocarpenes named aracarpene-1 (1) and aracarpene-2 (2) were isolated from wounded peanut seeds challenged by a strain of Aspergillus caelatus. The structures of these putative phytoalexins were determined by interpretation of NMR and MS data. The aracarpenes were investigated for their antifungal and antibacterial activities as well as antioxidant, anti-inflammatory, and cytotoxic activities in mammalian cells. Aracarpene-2 demonstrated high antibacterial properties against tested gram-positive and gram-negative bacteria, whereas aracarpene-1 displayed low antibacterial properties against the same bacteria. Both compounds had no antifungal activity against Aspergillus flavus. Together with peanut stilbenoids that are also produced in the challenged seeds, these compounds may represent a class of low-molecular weight peanut metabolites with a defensive role(s) against pathogenic microorganisms.

Candenatenins A-F, phenolic compounds from the heartwood of Dalbergia candenatensis

Chemical investigation of the CH2Cl2 extract of the heartwood of Dalbergia candenatensis affored six new phenolic compounds, designated candenatenins A-F (1-6), as well as four known compounds, (2R,3R)-3,5-dihydroxy-7-methoxyflavanone (7), 4-hydroxy-3-methoxy-8,9-methylenedioxypterocarpan (8), nutiducol (9), and sophoraflavanone A (10). The structures of the new compounds were determined by 1D- and 2D-NMR spectroscopic studies as well as by MS analysis. The cytotoxic activities of the isolated compounds are also reported.

DNA strand-scission by phloroglucinols and lignans from heartwood of Garcinia subelliptica Merr. and Justicia plants

Five 2,4,6-prenylated phloroglucinols, garcinielliptones HA (1), HB (2), HC (3), HD (4) and HE (5), were isolated from the heartwood of Garcinia subelliptica Merr. Their structures, including relative configurations, were elucidated by means of spectroscopic data analysis. The ability of phloroglucinols, 1-5 and lignans, tuberculatin (8), justicidin A (9), procumbenoside A (10) and ciliatosides A (11) and B (12), isolated from Justicia ciliata and Justicia procumbens, to induce DNA-cleavage activity was examined using pBR322, a supercoiled, covalently closed circular DNA, and it was analyzed by agarose gel electrophoresis. In the presence of Cu (II), compounds 3, 8, 10 and 11 caused significant breakage of supercoiled plasmid pBR322. The products were relaxed circles with no detectable linear forms. In the Cu(II)-mediated DNA damage of 3 and selective compound 8, Cu(I) was shown not to be an essential intermediate by using the Cu(I)-specific sequestering reagent neocuproine.

Pterocarpans phaseollin and neorautenol isolated from Erythrina addisoniae induce apoptotic cell death accompanied by inhibition of ERK phosphorylation

The genus Erythrina (Leguminosae), consisting of over 100 different species, is distributed in tropical regions. In traditional medicine, Erythrina species are used to treat cancer, but little is known about the anticancer mechanisms. From the stem bark of Erythrina addisoniae Hutch. & Dalziel, six prenylated pterocarpans were isolated and analysed for pharmacological activity: While calopocarpin, cristacarpin, orientanol c, and isoneorautenol showed only a weak or moderate toxicity in H4IIE hepatoma cells (EC(50)-value> 25 microM), the toxicity of neorautenol and phaseollin was in the low micromolar range (EC(50)-value: 1 and 1.5 microM, respectively). We further focused on these two substances showing that both increased caspase 3/7 activity and nuclear fragmentation as markers for apoptotic cell death. Neorautenol (10 microM, 2h), but not phaseollin induced the formation of DNA strand breaks (comet assay). Both substances showed no effect on NF-kappaB signalling (SEAP assay: basal activity and stimulation with TNF-alpha), on the other hand both pterocarpans (10 microM, 2 h) decreased the activation of the ERK kinase (p44/p42), an mitogen activated protein kinase which is associated with cell proliferation. We conclude that the pterocarpans phaseollin and neorautenol may be responsible for the anticarcinogenic actions of the plant extract reported in the literature. Further analysis of these substances may lead to new pharmacons to be used in cancer therapy.

Isolation of four new pterocarpans from Zygophyllum eurypterum (Syn. Z. atriplicoides) with enzyme-inhibition properties

Four new pterocarpans, atricarpan A (=(-)-1,2-dihydroxy-4-(hydroxymethyl)-3,9-dimethoxypterocarpan; 1), atricarpan B (=(-)-2,3-ethylenedioxy)-1,4-dihydroxy-9-methoxypterocarpan; 2), atricarpan C (=(-)-1,9-dimethoxypterocarpan-3-carboxylic acid; 3), and atricarpan D (=(-)-2,9-dimethoxy-4-(5-oxohexyl)pterocarpan; 4) were isolated from the BuOH extract of the whole plant of Zygophyllum eurypterum. The structure elucidations of those compounds were based primarily on 1D- and 2D-NMR analysis, including COSY, HMBC, and HMQC correlations. Compounds 1-4 also inhibited butyrylcholinesterase (BChE; EC 3.1.1.8) enzyme in a concentration-dependent manner with IC(50) values between 12.5-65.0 microM. Similarly, compounds 1 and 4 inhibited lipoxygenase (LOX; EC 1.13.11.12) and acetylcholinesterase (AChE; EC 3.1.1.7) enzymes with IC50 values of 13.5 and 20.5 muM, respectively.

Conformational Landscape of (R,R)-Pterocarpans with Biological Activity in Vacuo and in Aqueous Solution (PCM and/or Water Clusters)

All possible combinations of stable dihedral values have been considered in vacuo at the B3LYP/6-31G level for 3,9-dihydroxy-4,8-diprenylpterocarpan (erybraedin C), whose hydroxy out-out conformation had been examined earlier together with the conformational preferences of 3,9-dimethoxy-4-prenylpterocarpan (bitucarpin A) at the same level (Phys. Chem. Chem. Phys. 2004, 6, 2849). The structure with O5 trans with respect to H6a (O(t)) is about 2 kcal/mol less stable in vacuo than that with one of the H6 trans to it (H(t)); in aqueous solution its energy gap is nearly conserved. The in-in arrangement of the hydroxyl groups of erybraedin turns out to be preferred in vacuo (even considering zero point and thermal effects), where pseudo H-bonds are formed between hydroxy hydrogens and pi electron distributions of prenyl groups. The continuum solvent effect (water) at the IEF-PCM/B3LYP/6-31G level on the relative stability of the various rotamers is very limited both on bitucarpin and erybraedin. Considering the dihydrated derivatives, significant differences in the solvation energy are found between the distinct hydration sites, increasing in the order: methoxy O, ring O, hydroxy O, and hydroxy H. In hydroxy-water interactions, in fact, water prefers to behave as an H-bond acceptor unless nearby bulky groups prevent its approach. Interestingly enough, a bridging water molecule between the hydroxy H of erybraedin and the prenyl group can be found. The inclusion of BSSE corrections in hydroxy-water interactions decidedly favors out-out hydrated arrangements, followed by out-in and in-out ones. Bulk solvent effects with IEF-PCM about the dihydrated systems almost invert the stability order found in vacuo. When a four-water cluster is considered using QM methods, waters gather in H-bonded pairs around the solute OH groups. MD simulations, carried out on a pterocarpan solute (J. Phys. Chem. B 2005, 109, 16918), supply water adducts consistent with a liquid state that have also been embedded in the continuum solvent.

Phenolic acid amides: a new type of DNA strand scission agent from Piper caninum

In a survey of the active components of crude plant extracts for their ability to cleave DNA, a crude extract prepared from Piper caninum was found to induce the relaxation of supercoiled pBR322 plasmid DNA in the presence of Cu(2+). Bioassay-guided fractionation was carried out on this extract, guided by an in vitro DNA strand scission assay. Three active principles were isolated and identified as N-cis-feruloyl tyramine (1),N-trans-feruloyl tyramine (2), and 1-cinnamoylpyrrolidine (3). Compounds 1-3 represent a structurally new type of DNA strand scission agent.

A new pterocarpan, (-)-maackiain sulfate, from the roots ofSophora subprostrata

A new pterocarpan, (-)-maackiain 3-sulfate (1) was isolated from the methanol extract of roots of Sophora subprostarata together with (-)-maackiain (2), trifolirhizin (3), lupeol (4), ononin (5), 7,4'-dihydroxyflavone (6), and (+)-syringaresinol (7). The structure of 1 was determined by analyses of 2D NMR and HRFABMS. Compounds 5-7 were isolated from this plant for the first time.

Chiroptical properties and synthesis of enantiopure cis and trans pterocarpan skeleton

The first enantioselective synthesis of trans-(6aS,11aR)-pterocarpan [(+)-2] and its conversion to cis-(6aS,11aS)-pterocarpan [(+)-1] was achieved starting from racemic 2'-benzyloxyflavanone (rac-3). Their stereochemistry was deduced by X-ray analysis of the ketal intermediate (-)-5a. The CD study of (+)-1 and (+)-2 allows the configurational assignment of similar pterocarpan derivatives by CD spectroscopy.

A DNA strand-nicking principle of a higher plant, Caesalpinia sappan

To find anticancer agents from higher plants, DNA strand-scission assay method was employed for bioassay-guided fractionation as well as for screening the crude extracts. During the screening, an ethyl acetate extracts of the heartwood of Caesalpinia sappan L. (Leguminosae) exhibited potent DNA strand-scission activity. Therefore, the ethyl acetate extracts of the dried heartwood of C. sappan was subjected to the bioassay-guided fractionation, which led to the isolation of a known compound, brazilin (1) as the active constituent. In addition, caesalpine J (2) was also isolated as an inactive constituent.

Bioactive prenylated flavonoids from the stem bark of Artocarpus kemando

Four known prenylated flavonoids, artonins E (1) and O (2), artobiloxanthone (3), and cycloartobiloxanthone (4), were isolated from the stem bark of Artocarpus kemando by bioassay-guided fractionation using the DNA strand-scission and the KB cytotoxicity assays as monitors. Compounds 1 and 3 exhibited strong DNA strand-scission activity, and all four compounds were found to be cytotoxic.

Cytotoxic flavonoids from the stem bark of Lonchocarpus aff. fluvialis

Activity-guided fractionation of a chloroform-soluble extract of Lonchocarpus aff. fluvialis stem bark using a human epidermoid (KB) tumour cell line as a monitor afforded five rotenoids, one pterocarpan, one chalcone, three flavanones, one flavone and one triterpenoid. All of the compounds isolated proved to be of previously known structure. Among them, the rotenoids (-)-sumatrol and (+/-)-villosinol, the dibenzoylmethane derivative (+)-3,4-methylenedioxy-2'-methoxy-[2",3":4',3']-furanodibenzoylmethane, and the flavanones (-)-isoglabrachromene and (-)-candidone have been shown to exhibit significant cytotoxic activity against human cancer cells for the first time. This is the first report of the chemical constituents of this species, and the profile of compounds obtained was in accordance with the established chemosystematic patterns of species in the tribe Tephrosieae (Leguminosae, Papilionoideae).