Cyclopenta[b]benzofurans from Aglaia species with pronounced antifungal activity against rice blast fungus (Pyricularia grisea)

Direct Catalytic Asymmetric Conjugate Addition of Benzofuran-3(2H)-Ones to α,β-Unsaturated Thioamides: Stereodivergent Synthesis of Rocaglaol

Rocaglaol, a representative flavagline, has attracted significant attention because of its unique chemical structure and biological activities. This paper reports a mild and scalable copper-catalyzed enantioselective conjugate addition of benzofuran-3(2H)-ones to α,β-unsaturated thioamides. This method allows for the concise synthesis of all possible stereoisomers of a key intermediate of rocaglaol and its derivatives in a highly diastereo- and enantioselective manner using different chiral phosphine ligands. Theoretical insights into the reaction mechanism and the origin of ligand-dependent diastereodivergence were obtained using density functional theory calculations.

New dammarane-type triterpenoids from Aglaia elliptica (C.DC.) blume

Three new dammarane-type triterpenoids, namely elliptaglin A-C (1-3) were isolated from the stem bark of Aglaia elliptica (C.DC.) Blume along with three known derivatives, namely (20S)-hydroxydammar-24-en-3-on (4), cabralealactone (5), and E-25-hydroperoxydammar-23-en-20-ol-3-one (6). Subsequently, their chemical structures were determined using HR-ESI-MS, FTIR, 1D and 2D-NMR spectroscopic analysis as well as comparison with previous studies. The cytotoxicity activities of the isolated compounds against MCF-7 breast cancer and B16-F10 melanoma cell lines were then tested using PrestoBlue reagent. The analysis results showed that elliptaglin B (2) had the strongest activity against both cell lines with IC50 values of 60.98 and 51.83 µM, respectively.

The Cytotoxic Activity of Dammarane-Type Triterpenoids Isolated from the Stem Bark of Aglaia cucullata (Meliaceae)

The Aglaia genus, a member of the Meliaceae family, is generally recognized to include a number of secondary metabolite compounds with diverse structures and biological activities, including triterpenoids. Among the members of this genus, Aglaia cucullata has been reported to have unique properties and thrives exclusively in mangrove ecosystems. This plant is also known to contain various metabolites, such as flavaglines, bisamides, and diterpenoids, but there are limited reports on the isolation of triterpenoid compounds from its stem bark. Therefore, this research attempted to isolate and elucidate seven triterpenoids belonging to dammarane-type (1-7) from the stem bark of Aglaia cucullata. The isolated compounds included 20S,24S-epoxy-3α,25-dihydroxy-dammarane (1), dammaradienone (2), 20S-hydroxy-dammar-24-en-3-on (3), eichlerianic acid (4), (20S,24RS)-23,24-epoxy-24-methoxy-25,26,27-tris-nor dammar-3-one (5), 3α-acetyl-cabraleahydroxy lactone (6), and 3α-acetyl-20S,24S-epoxy-3α,25-dihydroxydammarane (7). Employing spectroscopic techniques, the chemical structures of the triterpenoids were identified using FTIR, NMR, and HRESITOF-MS. The cytotoxic activity of compounds 1-7 was tested with the PrestoBlue cell viability reagent against MCF-7 breast cancer, B16-F10 melanoma, and CV-1 normal kidney fibroblast cell lines. The results displayed that compound 5 had the highest level of bioactivity compared to the others. Furthermore, the IC₅₀ values obtained were more than 100 μM, indicating the low potential of natural dammarane-type triterpenoids as anticancer agents. These findings provided opportunities for further studies aiming to increase their cytotoxic activities through semi-synthetic methods.

Base-promoted cyclization of ortho-hydroxyacetophenones with in situ generated cyclopropenes: diastereoselective access to spirobenzo[b]oxepines and related precursors

An unprecedented [5 + 2] spirocyclization route to obtain a vital class of functionalized spirobenzo[b]oxepine-cyclopropanes in good to high yields with excellent diastereoselectivities is reported. This domino reaction proceeds through a regioselective oxa-Michael addition of ortho-hydroxyacetophenones as 1,5-binucleophiles to in situ produced highly reactive cyclopropenes from 2-aroyl-1-chlorocyclopropanecarboxylates triggered by Cs₂CO₃ and the subsequent intramolecular aldol reaction under heating conditions, enabling the formation of new C-O and C-C bonds for benzo[b]oxepine ring synthesis. Moreover, at ambient temperature, the above C-O/C-C bond-forming event takes place preferentially via a [4 + 2] annulation path over a spirocyclization route, leading to substituted fused-cyclopropanes with good diastereoselectivities. Gratifyingly, further alterations of the obtained spirobenzo[b]oxepines and tetrahydrocyclopropa[b]chromenes afford fascinating classes of 4H-chromen-4-ones and cyclopenta[c]chromenes, respectively, under metal-free conditions.

A parasitic fungus employs mutated eIF4A to survive on rocaglate-synthesizing Aglaia plants

Plants often generate secondary metabolites as defense mechanisms against parasites. Although some fungi may potentially overcome the barrier presented by antimicrobial compounds, only a limited number of examples and molecular mechanisms of resistance have been reported. Here, we found an Aglaia plant-parasitizing fungus that overcomes the toxicity of rocaglates, which are translation inhibitors synthesized by the plant, through an amino acid substitution in a eukaryotic translation initiation factor (eIF). De novo transcriptome assembly revealed that the fungus belongs to the Ophiocordyceps genus and that its eIF4A, a molecular target of rocaglates, harbors an amino acid substitution critical for rocaglate binding. Ribosome profiling harnessing a cucumber-infecting fungus, Colletotrichum orbiculare, demonstrated that the translational inhibitory effects of rocaglates were largely attenuated by the mutation found in the Aglaia parasite. The engineered C. orbiculare showed a survival advantage on cucumber plants with rocaglates. Our study exemplifies a plant-fungus tug-of-war centered on secondary metabolites produced by host plants.

Highly potent natural fungicides identified in silico against the cereal killer fungus Magnaporthe oryzae

Magnaporthe oryzae is one of the most notorious fungal pathogens that causes blast disease in cereals, and results in enormous loss of grain production. Many chemical fungicides are being used to control the pathogen but none of them are fully effective in controlling blast disease. Therefore, there is a demand for the discovery of a new natural biofungicide to manage the blast disease efficiently. A large number of new natural products showed inhibitory activities against M. oryzae in vitro. To find out effective biofungicides, we performed in silico molecular docking analysis of some of the potent natural compounds targeting four enzymes namely, scytalone dehydratase, SDH1 (PDB ID:1STD), trihydroxynaphthalene reductase, 3HNR (PDB ID:1YBV), trehalose-6-phosphate synthase, Tps1 (PDB ID:6JBI) and isocitrate lyase, ICL1 (PDB ID:5E9G) of M. oryzae fungus that regulate melanin biosynthesis and/or appresorium formation. Thirty-nine natural compounds that were previously reported to inhibit the growth of M. oryzae were subjected to rigid and flexible molecular docking against aforementioned enzymes followed by molecular dynamic simulation. The results of virtual screening showed that out of 39, eight compounds showed good binding energy with any one of the target enzymes as compared to reference commercial fungicides, azoxystrobin and strobilurin. Among the compounds, camptothecin, GKK1032A2 and chaetoviridin-A bind with more than one target enzymes of M. oryzae. All of the compounds except tricyclazole showed good bioactivity score. Taken together, our results suggest that all of the eight compounds have the potential to develop new fungicides, and remarkably, camptothecin, GKK1032A2 and chaetoviridin-A could act as multi-site mode of action fungicides against the blast fungus M. oryzae.

Dammarane-Type Triterpenoid from the Stem Bark of Aglaia elliptica (Meliaceae) and Its Cytotoxic Activities

Two new dammarane-type triterpenoid fatty acid ester derivatives, 3β-oleate-20S-hydroxydammar-24-en (1) and 3β-oleate-20S,24S-epoxy-25-hydroxydammarane (2) with a known dammarane-type triterpenoid compound, such as 20S-hydroxydammar-24-en-3-on (3), were isolated from the stem bark of Aglaiaelliptica (C.DC.) Blume. The chemical structures were determined by spectroscopic methods, including FTIR, NMR (one and two-dimensional), and HRESITOF-MS analysis, as well as chemical derivatization and comparison with previous literature. Furthermore, the synthetic analog resulting from transesterification of 1 and 2 also obtained 3β,20S-dihydroxy-dammar-24-en (4) and 20S,24S-epoxy-3β,25-dihydroxydammarane (5), respectively. The cytotoxic effect of all isolated and synthetic analog compounds was evaluated using PrestoBlue reagent against MCF-7 breast cancer cell and B16-F10 melanoma cell lines. The 20S-hydroxydammar-24-en-3-on (3) showed the strongest activity against MCF-7 breast cancer and B16-F10 melanoma cell, indicating that the ketone group at C-3 in 3 plays an essential role in the cytotoxicity of dammarane-type triterpenoid. On the other hand, compounds 1 and 2 had very weak cytotoxic activity against the two cell lines, indicating the presence of fatty acid, significantly decreasing cytotoxic activity. This showed the significance of the discovery to investigate the essential structural feature in dammarane-type triterpenoid, specifically for the future development of anticancer drugs.

Compounds for selective translational inhibition

Since many human diseases are caused by the unwelcome production of harmful proteins, compounds that selectively suppress protein synthesis should provide a unique path for drug development, expanding the druggable proteome. Although surveying the RNA/amino acid contexts that are preferentially affected by translation inhibitors has presented an analytic hurdle, the application of a technique termed ribosome profiling overcomes this problem. Indeed, this technique uncovers the selectivity of translation repression by small molecules such as chloramphenicol, macrolides, PF846, and rocaglates. The molecular understanding of how the compounds inspire context selectivity, despite their targeting to general translation machinery, facilitates rational drug design and discovery for therapeutic purposes.

Regio- and Diastereoselective Construction of Functionalized Benzo[b]oxepines and Benzo[b]azepines via Recyclable Gold(I)-Catalyzed Cyclizations

The heterogeneous gold-catalyzed cyclization of (o-alkynyl)phenoxy- or N-(o-alkynylphenyl)tolylsulfonamidoacrylates with alcohols has been developed by using an MCM-41-anchored diphenylphosphine-Au(I) complex [MCM-41-Ph₂P-AuNTf₂] as the catalyst under mild reaction conditions, yielding diverse functionalized benzo[b]oxepines or benzo[b]azepines with good to high yields and excellent diastereoselectivity. This heterogenized gold(I) catalyst exhibits a comparable activity to homogeneous Ph₃PAuNTf₂ and can be facilely recovered by a simple filtration of the reaction solution and reused more than seven times with almost a consistent catalytic efficiency.

Comparative phytochemistry of flavaglines (= rocaglamides), a group of highly bioactive flavolignans from Aglaia species (Meliaceae)

Flavaglines are formed by cycloaddition of a flavonoid nucleus with a cinnamic acid moiety representing a typical chemical character of the genus Aglaia of the family Meliaceae. Based on biosynthetic considerations 148 derivatives are grouped together into three skeletal types representing 77 cyclopenta[b]benzofurans, 61 cyclopenta[bc]benzopyrans, and 10 benzo[b]oxepines. Apart from different hydroxy, methoxy, and methylenedioxy groups of the aromatic rings, important structural variation is created by different substitutions and stereochemistries of the central cyclopentane ring. Putrescine-derived bisamides constitute important building blocks occurring as cyclic 2-aminopyrrolidines or in an open-chained form, and are involved in the formation of pyrimidinone flavaglines. Regarding the central role of cinnamic acid in the formation of the basic skeleton, rocagloic acid represents a biosynthetic precursor from which aglafoline- and rocaglamide-type cyclopentabenzofurans can be derived, while those of the rocaglaol-type are the result of decarboxylation. Broad-based comparison revealed characteristic substitution trends which contribute as chemical markers to natural delimitation and grouping of taxonomically problematic Aglaia species. A wide variety of biological activities ranges from insecticidal, antifungal, antiprotozoal, and anti-inflammatory properties, especially to pronounced anticancer and antiviral activities. The high insecticidal activity of flavaglines is comparable with that of the well-known natural insecticide azadirachtin. Comparative feeding experiments informed about structure-activity relationships and exhibited different substitutions of the cyclopentane ring essential for insecticidal activity. Parallel studies on the antiproliferative activity of flavaglines in various tumor cell lines revealed similar structural prerequisites that let expect corresponding molecular mechanisms. An important structural modification with very high cytotoxic potency was found in the benzofuran silvestrol characterized by an unusual dioxanyloxy subunit. It possessed comparable cytotoxicity to that of the natural anticancer compounds paclitaxel (Taxol®) and camptothecin without effecting normal cells. The primary effect was the inhibition of protein synthesis by binding to the translation initiation factor eIF4A, an ATP-dependent DEAD-box RNA helicase. Flavaglines were also shown to bind to prohibitins (PHB) responsible for regulation of important signaling pathways, and to inhibit the transcriptional factor HSF1 deeply involved in metabolic programming, survival, and proliferation of cancer cells. Flavaglines were shown to be not only promising anticancer agents but gained now also high expectations as agents against emerging RNA viruses like SARS-CoV-2. Targeting the helicase eIF4A with flavaglines was recently described as pan-viral strategy for minimizing the impact of future RNA virus pandemics.

Biological and biorational management of blast diseases in cereals caused by Magnaporthe oryzae

Blast diseases, caused by the fungal pathogen Magnaporthe oryzae, are among the most destructive diseases that occur on at least 50 species of grasses, including cultivated cereals wheat, and rice. Although fungicidal control of blast diseases has widely been researched, development of resistance of the pathogen against commercially available products makes this approach unreliable. Novel approaches such as the application of biopesticides against the blast fungus are needed for sustainable management of this economically important disease. Antagonistic microorganisms, such as fungi and probiotic bacteria from diverse taxonomic genera were found to suppress blast fungi both in vitro and in vivo. Various classes of secondary metabolites, such as alkaloids, phenolics, and terpenoids of plant and microbial origin significantly inhibit fungal growth and may also be effective in managing blast diseases. Common modes of action of microbial biocontrol agents include: antibiosis, production of lytic enzymes, induction of systemic resistance in host plant, and competition for nutrients or space. However, the precise mechanism of biocontrol of the blast fungus by antagonistic microorganisms and/or their bioactive secondary metabolites is not well understood. Commercial formulations of biocontrol agents and bioactive natural products could be cost-effective and sustainable but their availability at this time is extremely limited. This review updates our knowledge on the infection pathway of the wheat blast fungus, catalogs naturally occurring biocontrol agents that may be effective against blast diseases, and discusses their role in sustainable management of the disease.

Phytochemistry and biological activities of Aglaia species

Aglaia is the largest genus in the Meliaceae family (also known as Mahagoni in Indonesia), consisting of over 150 species, of which 65 are indigenous to Indonesia. These species spread through the tropical regions, especially Southeast Asia as well as the Nothern part of Australia, and have been used in traditional medicine for the treatment of several diseases. However, preliminary chemical researches commenced in 1965, where dammarane-type triterpenoids, aglaiol was isolated, and the structure was determined by chemical reaction and spectroscopic methods. Several studies have been carried out on the stembark, bark, leaves, seeds and leaves in the last fifty five years, and about 291 metabolites have been isolated from the sesquiterpenoid, diterpenoid, triterpenoid, limonoid, steroid, lignan, and alkaloid groups, as well as flavagline, which known to be the largest. This specifically amounts to 34% of Aglaia species, reported to show cytotoxic and insecticidal potentials, and also the tendency for use as chemical markers for this species. The extracts and compounds obtained from Aglaia species are evaluated for potential biological activities, including cytotoxicity, insecticidal, anti-inflammatory, antifungal, molluscicidal, antituberculosis and antiviral effects. In addition, flavagline (rocaglamide) derivatives have been confirmed to exhibit exceptional cytotoxicity, and are, thus, considered lead compounds for further development. Therefore, the results support the concept of utilizing Aglaia species as a potential source for the production of biologically active compounds.

Rocaglamide and silvestrol: a long story from anti-tumor to anti-coronavirus compounds

Covering: up to the beginning of 2020Many natural substances have been transformed again and again with regard to their pharmaceutical-medical potential, including new members of a growing class of natural products, the flavaglines. Important representatives are rocaglamide and silvestrol, isolated from the Aglaia species, which are highlighted here. These products started as potential anti-tumor agents five decades ago and have recently proved to be very promising antiviral agents, especially against RNA viruses. Today they are discussed as potential starting compounds for developing drug candidates and therapeutics.

Translation Inhibition by Rocaglates Activates a Species-Specific Cell Death Program in the Emerging Fungal Pathogen Candida auris

Fungal infections are a major contributor to infectious disease-related deaths worldwide. Recently, global emergence of the fungal pathogen Candida auris has caused considerable concern because most C. auris isolates are resistant to fluconazole, the most commonly administered antifungal, and some isolates are resistant to drugs from all three major antifungal classes. To identify novel agents with bioactivity against C. auris, we screened 2,454 compounds from a diversity-oriented synthesis collection. Of the five hits identified, most shared a common rocaglate core structure and displayed fungicidal activity against C. auris These rocaglate hits inhibited translation in C. auris but not in its pathogenic relative Candida albicans Species specificity was contingent on variation at a single amino acid residue in Tif1, a fungal member of the eukaryotic initiation factor 4A (eIF4A) family of translation initiation factors known to be targeted by rocaglates. Rocaglate-mediated inhibition of translation in C. auris activated a cell death program characterized by loss of mitochondrial membrane potential, increased caspase-like activity, and disrupted vacuolar homeostasis. In a rocaglate-sensitized C. albicans mutant engineered to express translation initiation factor 1 (Tif1) with the variant amino acid that we had identified in C. auris, translation was inhibited but no programmed cell death phenotypes were observed. This surprising finding suggests divergence between these related fungal pathogens in their pathways of cellular responses to translation inhibition. From a therapeutic perspective, the chemical biology that we have uncovered reveals species-specific vulnerability in C. auris and identifies a promising target for development of new, mechanistically distinct antifungals in the battle against this emerging pathogen.IMPORTANCE Emergence of the fungal pathogen Candida auris has ignited intrigue and alarm within the medical community and the public at large. This pathogen is unusually resistant to antifungals, threatening to overwhelm current management options. By screening a library of structurally diverse molecules, we found that C. auris is surprisingly sensitive to translation inhibition by a class of compounds known as rocaglates (also known as flavaglines). Despite the high level of conservation across fungi in their protein synthesis machinery, these compounds inhibited translation initiation and activated a cell death program in C. auris but not in its relative Candida albicans Our findings highlight a surprising divergence across the cell death programs operating in Candida species and underscore the need to understand the specific biology of a pathogen in attempting to develop more-effective treatments against it.

Phosphine-catalyzed dearomative (3 + 2) annulation of 2-nitrobenzofurans and nitrobenzothiophenes with allenoates

An efficient Ph₂PMe-catalyzed dearomative (3 + 2) annulation of 2-nitrobenzofurans, 2-nitrobenzothiophenes, and 3-nitrobenzothiophenes with allenoates is reported.

Fabrication of highly effective mosquito nanolarvicides using an Asian plant of ethno-pharmacological interest, Priyangu (Aglaia elaeagnoidea): toxicity on non-target mosquito natural enemies

Mosquitoes threaten the lives of humans, livestock, pets and wildlife around the globe, due to their ability to vector devastating diseases. Aglaia elaeagnoidea, commonly known as Priyangu, is widely employed in Asian traditional medicine and pest control. Medicinal activities include anti-inflammatory, analgesic, anticancer, and anesthetic actions. Flavaglines, six cyclopenta[b]benzofurans, a cyclopenta[bc]benzopyran, a benzo[b]oxepine, and an aromatic butyrolactone showed antifungal properties, and aglaroxin A and rocaglamide were effective to control moth pests. Here, we determined the larvicidal action of A. elaeagnoidea leaf aqueous extract. Furthermore, we focused on Priyangu-mediated synthesis of Ag nanoparticles toxic to Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi. The plant extract and the nanolarvicide were tested on three mosquito vectors, following the WHO protocol, as well as on three non-target mosquito predators. Priyangu-synthesized Ag nanoparticles were characterized by spectroscopic (UV, FTIR, XRD, and EDX) and microscopic (AFM, SEM, and TEM) analyses. Priyangu extract toxicity was moderate on Cx. quinquefasciatus (LC₅₀ 246.43; LC₉₀ 462.09 μg/mL), Ae. aegypti (LC₅₀ 229.79; LC₉₀ 442.71 μg/mL), and An. stephensi (LC₅₀ 207.06; LC₉₀ 408.46 μg/mL), respectively, while Priyangu-synthesized Ag nanoparticles were highly toxic to Cx. quinquefasciatus (LC₅₀ 24.91; LC₉₀ 45.96 μg/mL), Ae. aegypti (LC₅₀ 22.80; LC₉₀ 43.23 μg/mL), and An. stephensi (LC₅₀ 20.66; LC₉₀ 39.94 μg/mL), respectively. Priyangu extract and Ag nanoparticles were found safer to non-target larvivorous fishes, backswimmers, and waterbugs, with LC₅₀ ranging from 1247 to 37,254.45 μg/mL, if compared to target pests. Overall, the current research represents a modern approach integrating traditional botanical pesticides and nanotechnology to the control of larval populations of mosquito vectors, with negligible toxicity against non-target including larvivorous fishes, backswimmers, and waterbugs.

Enantioselective synthesis of cyclopenta[b]benzofurans via an organocatalytic intramolecular double cyclization

An enantioselective organocatalytic strategy, combining Brønsted base and N-heterocyclic carbene catalysis in a unique manner, is demonstrated for a concise construction of the privileged cyclopenta[b]benzofuran scaffold, present in many bioactive compounds having both academic and commercial interests. The reaction concept relies on an intramolecular one-pot double cyclization involving a cycle-specific enantioselective Michael addition followed by a benzoin condensation of ortho-substituted cinnamaldehydes. Cyclopenta[b]benzofurans were achieved in moderate to good yields, with excellent stereoselectivities. A proof of principle for a diastereodivergent variation is demonstrated through the synthesis of cyclopenta[b]benzofurans containing two contiguous aromatic substituents in a substitution pattern present in commercial and natural compounds. Furthermore, several transformations have been performed, demonstrating the synthetic utility of the products. Finally, insights into the activation mode and stereoindution models are presented for this new synthetic strategy.

Enantioselective addition of arylboronic acids to methyl 2-formylbenzoates by using a ruthenium/Me-BIPAM catalyst for synthesis of chiral 3-aryl-isobenzofuranones

[RuCl₂(p-cymene)]₂/Me-BIPAM and RuCl₂(PPh₃)₃/Me-BIPAM catalyst systems tolerate a variety of functional groups and give high yields with high enantioselectivities.

Rocaglamide, silvestrol and structurally related bioactive compounds from Aglaia species

Covering: 2006 to 2013. Investigations on the chemistry and biology of rocaglamide, silvestrol and structurally related bioactive compounds from Aglaia species during the period 2006-2013 are reviewed. Included are new phytochemical studies of naturally occurring rocaglamide derivatives, an update on synthetic methods for cyclopenta[b]benzofurans, and a description of the recent biological evaluation and mechanism-of-action studies on compounds of this type.

Microwave-assisted preparation and antimicrobial activity of O-alkylamino benzofurancarboxylates

ABSTRACT

A series of derivatives of 2 and 3-benzofurancarboxylates were synthesized under microwave-assisted conditions. Their in-vitro antimicrobial properties were assessed. Inhibition by the compounds of the growth of antibiotic-susceptible standards and clinically isolated strains of Gram-positive and Gram-negative bacteria, yeasts, and a human fungal pathogen was moderate to significant. Methyl 5-bromo-7-[2-(N,N-diethylamino)ethoxy]-6-methoxy-2-benzofurancarboxylate hydrochloride was identified as the most active compound (MIC 3-12 × 10-3 μmol/cm3 against Gram-positive bacteria; MIC 9.4 × 10-2 μmol/cm3 against Candida and Aspergillus brasiliensis). The molecular and crystal structures of 2-(N,N-diethylamino)ethyl 6-acetyl-5-hydroxy-2-methyl-3-benzofurancarboxylate were established by single-crystal X-ray diffraction.

GRAPHICAL ABSTRACT

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Antipoliovirus Activity of the Organic Extract of Eupatorium buniifolium: Isolation of Euparin as an Active Compound

The antiviral activity of the organic extract (OE) of Eupatorium buniifolium against poliovirus type 1 was determined by in vitro assays with an effective concentration 50 (EC₅₀) of 23.3 ± 3.3 µg/mL. Bioassay-guided fractionation of the OE allowed the isolation of an active principle that was identified by spectroscopic methods (¹H- and ¹³C-NMR, EI-MS, UV, and IR spectroscopy) as the benzofuran euparin. The plaque reduction assay in Vero cells was used to assess the antiviral activity of euparin against poliovirus types 1, 2, and 3 with EC₅₀ values of 0.47, 0.12, and 0.15 µg/mL, respectively. Moreover, this compound showed high selectivity indexes of 284.9, 1068, and 854.7, respectively. In order to identify the mechanism by which euparin exerts its antiviral activity, the virucidal effect, the pretreatment of Vero cells, and the time of action on one viral replication cycle were evaluated. Results obtained demonstrated that euparin exerts its effect during the early events of the replication cycle, from the virus adsorption to cells up to the first twenty minutes after infection. This is the first report on the presence of euparin in E. buniifolium and its antiviral activity.

Activity of selected phytochemicals against Plasmodium falciparum

According to the WHO, in 2008, there were 247 million reported cases of malaria and nearly one million deaths from the disease. Parasite resistance against first-line drugs, including artemisinin and mefloquine, is increasing. In this study the plant-derived compounds aglafolin, rocaglamid, kokusaginine, arborine, arborinine and tuberostemonine were investigated for their anti-plasmodial activity in vitro. Fresh Plasmodium falciparum isolates were taken from patients in the area of Mae Sot, north-western Thailand in 2008 and the inhibition of schizont maturation was determined for the respective compounds. With inhibitory concentrations effecting 50%, 90% and 99% inhibition (IC(50), IC(90) and IC(99)) of 60.95 nM, 854.41 nM and 7351.49 nM, respectively, rocaglamid was the most active of the substances, closely followed by aglafoline with 53.49 nM, 864.55 nM and 8354.20 nM. The activity was significantly below that of artemisinin, but moderately higher than that of quinine. Arborine, arborinine, tuberostemonine and kokusaginine showed only marginal activity against P. falciparum characterized by IC(50) and IC(99) values higher than 350 nM and 180 μM, respectively, and regressions with relatively shallow slopes S>14.38. Analogues of rocaglamid and aglafoline merit further exploration of their anti-plasmodial activity.

Biologically active constituents of Aglaia erythrosperma

From the fruits and leaves of Aglaia erythrosperma (Meliaceae), 10 chemical constituents were isolated and identified, i.e. the dammarane triterpenoids cabraleadiol (1), cabraleahydroxylactone (2), ethyl eichlerianoate (3), eichlerialactone (4), aglinin A (5), cabralealactone (6), the aglaialactone 5,6-desmethylenedioxy-5-methoxy-aglalactone (7), the flavagline 4'-demethoxy-3',4'-methylenedioxy-methyl rocaglate (8) and two coumarins: scoparone and scopoletin. Flavagline 8 exhibited antimalarial activity with an IC(50) value of 7.30 µg mL(-1) and was strongly cytotoxic against small cell lung cancer (NCI-H187), epidermoid carcinoma (KB) and breast cancer (BC) cell lines, with IC(50) values of 2.17, 2.10 and 0.11 µg mL(-1), respectively. Aglinin A (5) displayed moderate cytotoxicity against all the three cancer cell lines, whereas ethyl eichlerianoate (3), cabralealactone (6) and the aglaialactone 7 were exclusively cytotoxic to NCI-H187 cell line. Cabraleahydroxylactone (2) showed antiviral activity against herpes simplex virus type-1 with an IC(50) value of 3.20 µg mL(-1), in comparison with the standard acyclovir (IC(50) = 1.90 µg mL(-1)). When tested for antimycobacterial activity against Mycobacterium tuberculosis H(37)Ra, compounds 1-4 and 6-8 displayed minimum inhibitory concentration in the range of 25-50 µg mL(-1).

Anti-leishmanial activity of plant-derived acridones, flavaglines, and sulfur-containing amides

Visceral and cutaneous leishmaniases are an important public health problem in endemic geographic regions in 88 countries worldwide, with around 12 million infected people. Treatment options are limited due to toxicity and teratogenicity of the available drugs, response problems in HIV/Leishmania co-infections, and upcoming resistances. In this study, we investigated the anti-leishmanial activity of 13 plant-derived compounds in vitro aiming to find new drug candidates. Toxicity of the compounds was evaluated in human primary hepatocytes, and hemolytic activity was examined in freshly isolated erythrocytes. Two acridones, 5-hydroxynoracronycine and yukocitrine, two flavaglines, aglafoline and rocaglamide, and the sulfur-containing amide methyldambullin showed promising anti-leishmanial activities with 50% effective concentrations (EC50s) of 34.84, 29.76, 7.45, 16.45, and 6.29 μM, respectively. Hepatotoxic activities of 5-hydroxynoracronycine, yukocitrine, and methyldambullin were significantly lower compared to miltefosine and lower or equal compared to artesunate, whereas the ones of rocaglamide and aglafoline were slightly higher compared to miltefosine and significantly higher compared to artesunate. None of the compounds showed hemolytic activity.

Triterpenoids from Aglaia abbreviata and their cytotoxic activities

Six new triterpenoids (1-6), along with 10 known compounds, were isolated from the stems of Aglaia abbreviata. The structures of 1-6 were elucidated on the basis of their spectroscopic data. Compounds 1-6 were evaluated for their cytotoxic activities against a small panel of human tumor cell lines.

Pd-NHC catalyzed cyclopentannulation of diazabicyclic alkenes with ortho-aryl halides

Pd-NHC catalyzed cyclopentannulation of diazabicyclic alkenes with ortho- functionalized aryl halides is described. In all the reactions, a single diastereomer of the cyclopentannulated product is observed, and this reaction is very efficient under microwave irradiation.

Absolute configuration of odorine

The title compound, known as odorine or roxburghiline {systematic name: (S)-N-[(R)-1-cinnamoylpyrrolidin-2-yl]-2-methyl­butanamide}, C₁₈H₂₄N₂O₂, is a nitro­genous compound isolated from the leaves of Aglaia odorata. The absolute configuration was determined by refinement of the Flack parameter with data collected using Cu Kα radiation showing positions 2 and 2′ to be S and R, respectively. The pyrrolidine ring adopts an envelope conformation. In the crystal, mol­ecules are linked into chains along [010] by inter­molecular N—H⋯O hydrogen bonds.

Terpenoid constituents and antifungal activity of Aglaia forbesii seed against phytopathogens

Two new trisnortriterpenoids possessing a γ-lactone ring linked to the D-ring of a 3,4-secodammarane skeleton in a 20R configuration, named isoeichlerialactone (1) and methyl isoeichlerialactone (2), were isolated from the seed of Aglaia forbesii , along with the three dammarane triterpenes, isocabralealactone (3), isoeichlerianic acid (4), and aglinin A (5), the sesquiterpene spathulenol (6), and the widespread sterols β-sitosterol and stigmasterol. Their structures were established based on detailed spectroscopic analysis. Antifungal activity of A. forbesii seed against three phytopathogens, Phytophthora botryosa , P. palmivora , and Rigidoporus microporus , was carried out using the mycelium inhibition test and broth microdilution technique. Superior activity was exhibited by hexane and dichloromethane fractions containing the compounds 1, 4, and 5 as the main components. Subsequent antiphytopathogenic fungi tests proved that compounds 1, 4, and 5 possessed good antifungal activity.

Absolute configuration of isoeichlerialactone

The title seco-dammarane triterpenoid, C(27)H(42)O(4) (systematic name: 3-{(3S,3aR,5aR,6S,7S,9aR,9bR)-6,9a,9b-trimethyl-3-[(R)-2-methyl-5-oxotetra-hydro-furan-2-yl]-7-(prop-1-en-2-yl)dodeca-hydro-1H-cyclo-penta-[a]naphthalen-6-yl}propanoic acid), has been isolated for the first time from the seeds of Aglaia forbesii. The mol-ecule has three fused rings and all rings are in trans-fused. The two cyclo-hexane rings are in standard chair conformations and the cyclo-pentane ring adopts an envelope conformation. Its absolute configuration was determined by the refinement of the Flack parameter to 0.26 (17). In the crystal, mol-ecules are linked into chains along [010] by O-H⋯O hydrogen bonds.

6α-Acetoxy-gedunin

THE TITLE COMPOUND [SYSTEMATIC NAME: (1S,3aS,4aR,4bS,5S,6R,6aR,10aR,10bR,12aS)-5,6-bis-(acet-yloxy)-1-(3-fur-yl)-1,5,6,6a,7,10a,10b,11,12,12a-deca-hydro-4b,7,7,10a,12a-penta-methyl-oxireno[c]phenanthro[1,2-d]pyran-3,8(3aH,4bH)-dione], C(30)H(36)O(9), is a limonoid-type triterpene isolated from Aglaia elaeagnoidea (A. Juss.) Benth. (Meliaceae) from Queensland, northern Australia. It contains the gedunin core of four trans-fused six-membered rings with an oxirane ring annelated to the fourth ring. A terminal 3-furyl unity and two acet-oxy groups in a mutual cis-disposition supplement the mol-ecule. A comparison between the gedunin cores of the title compound, the parent compound gedunin, and three further gedunin derivatives revealed considerable variations in their conformation stemming from the conformational lability of the first screw-boat ring and the third twist-boat ring. A sensitive measure for the third ring is one C-C-C-C torsion angle, which is 14.2 (2)° in the title compound, but varies in other cases from ca 20 to ca -40°. In the crystalline state, 6α-acetoxy-gedunin shows ten comparatively weak C-H⋯O inter-actions, with H⋯O distances in the range of 2.33-2.69 Å.

Amide-esters from Aglaia tenuicaulis--first representatives of a class of compounds structurally related to bisamides and flavaglines

Six amide-esters and two sulphur-containing bisamides were isolated from the leaves, stem and root bark of Aglaia tenuicaulis together with two bisamides from the leaves of A. spectabilis. Their structures were elucidated by spectroscopic methods. The co-occurrence of amide-esters and bisamides suggests close biosynthetic connections replacing only one nitrogen atom of putrescine with oxygen. Putrescine appears to be the common building block linked to various acids from which the cinnamoyl moiety represents the prerequisite for an incorporation of bisamides into flavaglines. Corresponding amide-esters are apparently not incorporated, but closely related amide-alcohol derivatives were found as part of benzopyran and benzofuran flavaglines. The structure of a amide-alcohol is described, representing an artifact due to hydrolysis of an amide-ester during TLC purification. A hypothetical amide-amine building block is suggested to form the characteristic pyrimidinone structures only found in benzofuran flavaglines. Structural and biosynthetic connections between amide-esters, bisamides and flavaglines are discussed and the chemotaxonomic significance of accumulating specific derivatives within the genus Aglaia is highlighted.

Flavaglines and triterpenoids from the leaves of Aglaia forbesii

Three structurally complex flavaglines of the cyclopenta[bc]benzopyran type, named desacetylpyramidaglains A, C, D (1-3), and the triterpene 23, 24, 25-trihydroxycycloartan-3-one (4) were isolated from the leaves of Aglaia forbesii together with the two rare pregnane steroids 2beta,3beta-dihydroxy-5alpha-pregn-17(Z)-en-16-one and 2beta,3beta-dihydroxy-5alpha-pregn-17(E)-en-16-one, as well as the bisamide pyramidatine, the sesquiterpene spathulenol, and the widespread triterpenoids lupeol, lupenone, and a mixture of beta-sitosterol and stigmasterol. Their structures were elucidated by 1D and 2D NMR spectroscopy and mass spectrometry. Compounds 3, 4, 5, and 6 were tested for antituberculosis and antiviral activity.

Activity-guided isolation of cytotoxic constituents from the bark of Aglaia crassinervia collected in Indonesia

Activity-guided fractionation of a CHCl(3)-soluble partition of the MeOH extract of the bark of Aglaia crassinervia collected in Indonesia led to the isolation of three new glabretal-type triterpenoids, aglaiaglabretols A-C (1-3), as well as nine known compounds, 3-epi-cabraleahydroxylactone (4), cabraleahydroxylactone (5), rocaglaol (6), 2beta,3beta-dihydroxy-5alpha-pregn-17(20)-(E)-16-one, scopoletin, and mixtures of cabraleadiol and epicotillol and of beta-sitosterol and stigmasterol. The structures of compounds 1-3 were determined on the basis of spectroscopic and chemical methods. The structure of aglaiaglabretol A (1) was confirmed by single-crystal X-ray analysis, and the absolute stereochemistry of this isolate was established by the Mosher ester method. The cytotoxic activity of all isolates and several chemical transformation products obtained in the present study was evaluated. The known cyclopenta[b]benzofuran, rocaglaol (6), was found to be significantly active and comparable in potency to the positive controls, paclitaxel and camptothecin. Aglaiaglabretol B (2) was further tested in an in vivo hollow fiber model.

Antifungal 3-butylisocoumarins from Asteraceae-Anthemideae

Seven new naturally occurring 3-butylisocoumarins were isolated and identified from lipophilic extracts of aerial as well as underground organs: corfin (17) and 3'-hydroxycorfin (18) from the roots of Chamaemelum mixtum and (-)-(R)-2'-methoxydihydroartemidin (5), (+)-(S,R)-epoxyartemidin (6a), dracumerin (12), (+)-(R)-(E)-3'-hydroxyartemidin (13), and capillarin isovalerate (20) from various organs of Artemisia dracunculus (tarragon). Furthermore, six known derivatives, artemidiol (7), (E/Z)-artemidin (11), capillarin (19), artemidinol (21), 8-hydroxyartemidin (22), and 8-hydroxycapillarin (23), were obtained. The antifungal activities of all naturally occurring derivatives were determined in a germ-tube inhibition test against a susceptible strain of rice blast fungus Pyricularia grisea. The 3-butyl side-chain is a prerequisite for high activity. Eleven structurally related synthetic derivatives were additionally tested to explore the influence of structural characteristics on activity. Benlate, blasticidin S, kresoxim-methyl, griseofulvin, and the carrot phytoalexin 6-methoxymellein all served as positive controls.

Dihydrophenanthrenes and other antifungal stilbenoids from Stemona cf. pierrei

Three new dihydrophenanthrenes, stemanthrenes A-C, along with the new dihydrostilbene stilbostemin G were isolated and identified from the underground parts of Stemona cf. pierrei together with the known pinosylvin, 4'-methylpinosylvin, dihydropinosylvin, stilbostemins B, D, and E as well as the pyrrolo[1,2-a]azepine alkaloids protostemonine and stemonine. The structures of all new stilbenoids, elucidated by NMR analyses, showed a common substitution pattern for aromatic ring A and characteristic C-methylations for ring B. The trivial name racemosol, previously reported for S. collinsae, was renamed to stemanthrene D due to its priority for another compound. Bioautographic tests on TLC plates with Cladosporium herbarum displayed high antifungal activity for compounds with an unsubstituted aromatic ring A, e.g. pinosylvin, but only weak effects for the higher substituted stilbostemin G and stemanthrenes A-C. Similar results were obtained by germ tube inhibition of five microfungi using 2-fold serial broth dilutions determined by a microplate reader. Because of weak inhibition and chemical instability of stemanthrenes, no EC(50) and EC(90) values could be calculated.

Antifungal stilbenoids from Stemona collinsae

Fifteen new stilbenoids including 11 phenylbenzofurans, the stemofurans A-K (1-11), and four dihydrostilbenes, the stilbostemins A (15), C (17), E (19), and F (20), were isolated and identified from a methanolic extract of Stemona collinsae roots together with five known derivatives, the stilbenes pinosylvin (13) and 4'-methylpinosylvin (14), the dihydrostilbenes, stilbostemins B (16) and D (18), and the dihydrophenanthrene racemosol (12) as well as (+)-sesamin, coniferyl alcohol, and stigmasterol. Bioautographic tests with Cladosporium herbarum displayed antifungal activity for stilbenoids of all four structural types. Ten derivatives were tested against five microfungi using the microdilution technique linked with digital image analysis of germ tubes.