Cytotoxic compounds from Mundulea chapelieri from the Madagascar Rainforest

Antiplasmodial and antileishmanial flavonoids from Mundulea sericea

Five known compounds (1-5) were isolated from the extract of Mundulea sericea leaves. Similar investigation of the roots of this plant afforded an additional three known compounds (6-8). The structures were elucidated using NMR spectroscopic and mass spectrometric analyses. The absolute configuration of 1 was established using ECD spectroscopy. In an antiplasmodial activity assay, compound 1 showed good activity with an IC₅₀ of 2.0 μM against chloroquine-resistant W2, and 6.6 μM against the chloroquine-sensitive 3D7 strains of Plasmodium falciparum. Some of the compounds were also tested for antileishmanial activity. Dehydrolupinifolinol (2) and sericetin (5) were active against drug-sensitive Leishmania donovani (MHOM/IN/83/AG83) with IC₅₀ values of 9.0 and 5.0 μM, respectively. In a cytotoxicity assay, lupinifolin (3) showed significant activity on BEAS-2B (IC₅₀ 4.9 μM) and HePG2 (IC₅₀ 10.8 μM) human cell lines. All the other compounds showed low cytotoxicity (IC₅₀ > 30 μM) against human lung adenocarcinoma cells (A549), human liver cancer cells (HepG2), lung/bronchus cells (epithelial virus transformed) (BEAS-2B) and immortal human hepatocytes (LO2).

Cytotoxicity and Brine Shrimp Lethality of Rotenoids and Extracts from Sarcolobus globosus

The present study was performed to examine the brine shrimp toxicity and cytotoxic effect of the mangrove plant Sarcolobus globosus. The Et2O and EtOAc extracts were toxic to brine shrimp larvae (LC50 = 1.6 and 4.0 μg/mL) and Caco-2 cells (IC50 = 6.7 and 21.2 μg/mL). Three rotenoids isolated from S. globosus, tephrosin, sarcolobin and 12a-hydroxyrotenone, showed high toxicity in the brine shrimp assay with LC50 values of 2.2, 2.8 and 1.9 μM, respectively.

Antiplasmodial prenylated flavanonols from Tephrosia subtriflora

The CH₂Cl₂/MeOH (1:1) extract of the aerial parts of Tephrosia subtriflora afforded a new flavanonol, named subtriflavanonol (1), along with the known flavanone spinoflavanone B, and the known flavanonols MS-II (2) and mundulinol. The structures were elucidated by the use of NMR spectroscopy and mass spectrometry. The absolute configuration of the flavanonols was determined based on quantum chemical ECD calculations. In the antiplasmodial assay, compound 2 showed the highest activity against chloroquine-sensitive Plasmodium falciparum reference clones (D6 and 3D7), artemisinin-sensitive isolate (F32-TEM) as well as field isolate (KSM 009) with IC₅₀ values 1.4-4.6 μM without significant cytotoxicity against Vero and HEp2 cell lines (IC₅₀ > 100 μM). The new compound (1) showed weak antiplasmodial activity, IC₅₀ 12.5-24.2 μM, but also showed selective anticancer activity against HEp2 cell line (CC₅₀ 16.9 μM).

Synthesis of natural-like acylphloroglucinols with anti-proliferative, anti-oxidative and tube-formation inhibitory activity

Two series of natural and natural-like mono- and bicyclic acylphloroglucinols derived from secondary metabolites in the genus Hypericum (Hypericaceae) were synthesised and tested in vitro for anti-proliferative and tube-formation inhibitory activity in human microvascular endothelial cells (HMEC-1). In addition, their anti-oxidative activity was determined via an ORAC-assay. The first series of compounds (4a-e) consisted of geranylated monocyclic acylphloroglucinols with varying aliphatic acyl substitution patterns, which were subsequently cyclised to the corresponding 2-methyl-2-prenylchromane derivatives (5a and 5d). The second series involved compounds containing a 2,2-dimethylchromane skeleton with differing aromatic acyl substitution (6a-d and 7a-e). Compound 7a, (5,7-dihydroxy-2,2-dimethylchroman-6-yl)-(3,4-dihydroxyphenyl)methanone), showed the highest in vitro anti-proliferative activity with an IC50 of 0.88 ± 0.08 μM and a remarkable anti-oxidative activity of 2.8 ± 0.1 TE from the ORAC test. Interestingly, the high anti-proliferative activity of these acylphloroglucinols was not associated with tube-formation inhibition. Compounds (E)-1-(3-(3,7-dimethylocta-2,6-dien-1-yl)-2,4,6-trihydroxyphenyl)-2-methylbutan-1-one (4d) and (5,7-dihydroxy-2,2-dimethylchroman-6-yl)(3,4-dimethoxyphenyl)methanone (6a) exhibited moderate to weak anti-proliferative effects (IC50 11.0 ± 1 μM and 48.0 ± 4.3 μM, respectively) and inhibited the capillary-like tube formation of HMEC-1 in vitro, whereas 7a was inactive. The most active compound in the ORAC assay was 7c, which exhibited an anti-oxidative effect of 6.6 ± 1.0 TE. However, this compound showed only weak activity during the proliferation assay (IC50 53.8 ± 0.3) and did not inhibit tube-formation.

Synthesis and structure elucidation of a series of pyranochromene chalcones and flavanones using 1D and 2D NMR spectroscopy and X-ray crystallography

A series of novel pyranochromene chalcones and corresponding flavanones were synthesized. This is the first report on the confirmation of the absolute configuration of chromene-based flavanones using X-ray crystallography. These compounds were characterized by 2D NMR spectroscopy, and their assignments are reported herein. The 3D structure of the chalcone 3b and flavanone 4g was determined by X-ray crystallography, and the structure of the flavanone was confirmed to be in the S configuration at C-2.

Synthesis of sulfonylhydrazone- and acylhydrazone-substituted 8-ethoxy-3-nitro-2H-chromenes as potent antiproliferative and apoptosis inducing agents

3-Nitro-2H-chromenes have recently been identified as a novel class of potent antitumor agents. In view of the favorable effects shown by sulfonylhydrazones and acylhydrazones, we designed and synthesized a series of sulfonylhydrazone- and acylhydrazone-substituted 8-ethoxy-3-nitro-2H-chromene derivatives, and evaluated their cell growth inhibition activities against A549, KG-1, A2780, and K562 cells. All the tested compounds exhibited more potent antiproliferative activity than BENC-511 against KG-1 cells. These compounds displayed IC50 values in the nanomolar range against A2780 cells. Compound 7d showed prominent cytotoxicity against K562 cells with an IC50 of 0.11 µM, which was comparable to that of BENC-511. Compound 7d arrested K562 cells at the G1 phase at high concentrations and induced apoptosis in K562 cells. Furthermore, 7d increased the levels of cleaved caspase-3, decreased the expression of bcl-2 and induced the cleavage of poly(ADP-ribose) polymerase in K562 cells. Thus, this study provides the development of a series of novel compounds as effective antitumor agents with apoptotic death ability.

Rhodium catalyzed oxidative coupling of salicylaldehydes with diazabicyclic olefins: a one pot strategy involving aldehyde C-H cleavage and π-allyl chemistry towards the synthesis of fused ring chromanones

An efficient one pot strategy for the synthesis of cyclopentene fused chromanone derivatives through the direct oxidative coupling of salicylaldehydes with bicyclic olefins in the presence of a rhodium-copper catalyst system is described. This is the first report on the ring opening-ring closing of bicyclic hydrazines via metal catalyzed oxidative coupling reaction.

Fast method for the simultaneous quantification of toxic polyphenols applied to the selection of genotypes of yam bean (Pachyrhizus sp.) seeds

The purpose of the research was to develop and validate a rapid quantification method able to screen many samples of yam bean seeds to determine the content of two toxic polyphenols, namely pachyrrhizine and rotenone. The analytical procedure described is based on the use of an internal standard (dihydrorotenone) and is divided in three steps: microwave assisted extraction, purification by solid phase extraction and assay by ultra high performance liquid chromatography (UHPLC). Each step was included in the validation protocol and the accuracy profiles methodology was used to fully validate the method. The method was fully validated between 0.25 mg and 5 mg pachyrrhizin per gram of seeds and between 0.58 mg/g and 4 mg/g for rotenone. More than one hundred samples from different accessions, locations of growth and harvest dates were screened. Pachyrrhizine concentrations ranged from 3.29 mg/g to lower than 0.25 mg/g while rotenone concentrations ranged from 3.53 mg/g to lower than 0.58 mg/g. This screening along with principal component analysis (PCA) and discriminant analysis (DA) analyses allowed the selection of the more interesting genotypes in terms of low concentrations of these two toxic polyphenols.

Gold(I)-catalyzed hydroarylation reaction of aryl (3-iodoprop-2-yn-1-yl) ethers: synthesis of 3-iodo-2H-chromene derivatives

An efficient entry to the preparation of elusive 4-unsubstituted-3-iodo-2H-chromenes has been accomplished as result of a catalytic cyclization. Thus, upon exposition of [(3-iodoprop-2-yn-1-yl)oxy]arenes to IPrAuNTf₂ (3 mol %), in 1,4-dioxane at 100 °C, the desired heterocyclic motif is readily assembled. This process nicely tolerates a variety of functional groups and, interestingly, it is compatible with the presence of strong electron-withdrawing groups attached to the arene. The overall transformation can be termed as a new example of a migratory cycloisomerization and, formally, it involves well-blended 1,2-iodine shift and hydroarylation steps.

Pierreiones A-D, solid tumor selective pyranoisoflavones and other cytotoxic constituents from Antheroporum pierrei

Bioassay-guided fractionation of a solid tumor selective extract of the leaves and twigs of Antheroporum pierrei acquired from the U.S. National Cancer Institute extract repository afforded four new pyranoisoflavones, pierreiones A-D (1-4), together with rotenone (5), 12a-hydroxyrotenone (6), and tephrosin (7). The structures of all new compounds were determined on the basis of their spectroscopic data, and the absolute configuration of 1 was assigned with the help of (1)H NMR analysis of its Mosher's ester derivatives. Compounds 1 and 5-7 accounted for the majority of the biological activity in terms of either cytotoxicity and/or selective toxicity to solid tumor cell lines. Pierreiones A (1) and B (2) demonstrated solid tumor selectivity with minimal cytotoxicity, while pierreione C (3) exhibited no activity.

Antiproliferative compounds from Pongamiopsis pervilleana from the Madagascar Dry Forest

Bioassay-guided fractionation of an ethanol extract of the roots of the endemic Malagasy plant Pongamiopsis pervilleana led to the isolation of the three new compounds (2'R)-4'-hydroxyemoroidocarpan (1), pongavilleanine (3), and epipervilline (4) together with two known compounds, identified as emoroidocarpan (2) and rotenolone (5). The structures of all compounds were determined by physical, chemical, and spectroscopic evidence. The stereochemistry at C-2' of the previously reported compound emoroidocarpan was determined to be R by the observation of a negative Cotton effect at 474 nm in the CD spectrum of its osmate ester derivative. Compounds 2-5 displayed moderate antiproliferative activity against the A2780 human ovarian cancer cell line, and rotenolone also showed micromolar antiproliferative activity toward the breast cancer BT-549, prostate cancer DU 145, NSCLC NCI-H460, and colon cancer HCC-2998 cell lines.

Biodiversity conservation and drug discovery: Can they be combined? The Suriname and Madagascar experiences

The approach to new drugs through natural products has proved to be the single most successful strategy for the discovery of new drugs, but in recent years its use has been deemphasized by many pharmaceutical companies in favor of approaches based on combinatorial chemistry and genomics, among others.Drug discovery from natural sources requires continued access to plant, marine, and microbial biomass, and so the preservation of tropical rainforests is an important part of our drug discovery program. Sadly, many of the tropical forests of the world are under severe environmental pressure, and deforestation is a serious problem in most tropical countries. One way to combat this loss is to demonstrate their value as potential sources of new pharmaceutical or agrochemical products.As part of an effort to integrate biodiversity conservation and drug discovery with economic development, we initiated an International Cooperative biodiversity Group (ICBG) to discover potential pharmaceuticals from the plant biodiversity of Suriname and Madagascar. The Group, established with funding from agencies of the United States government, involved participants from the USA, Suriname, and Madagascar. The basic approach was to search for bioactive plants in the Suriname and Malagasy flora, and to isolate their bioactive constituents by the best available methods, but the work included capacity building as well as research. Progress on this project will be reported, drawing on results obtained from the isolation of bioactive natural products from Suriname and Madagascar. The benefits of this general approach to biodiversity and drug discovery will also be discussed.

Naturally Occurring Flavanones: An Overview

Flavanones are one of the most interesting naturally occurring flavonoids in view of their structural pattern as well as biological and pharmacological potentials. The present review deals with natural flavanones reported from 1998 to mid 2007, along with their biological and pharmacological activities. The review includes more than 160 new naturally occurring flavanones from 135 references. The reported flavonoids belong to thirty-six plant families.

Cytotoxic diterpenoids from Podocarpus madagascariensis from the Madagascar rainforest

Bioassay-directed fractionation of an extract of the root and bark of Podocarpus madagascariensis resulted in the isolation of a new totarol diterpenoid (1) in addition to the three known cytotoxic diterpenoids 19-hydroxytotarol (2), totaradiol (3), and 4beta-carboxy-19-nor-totarol (4). The structure of the new compound 1 was established as methyl-13-hydroxy-14-isopropyl-9(11),12,14(8)-podocarpatriene-19-oate on the basis of 1D and 2D NMR spectroscopic interpretation and methylation of 4. All the compounds exhibited cytotoxic activity against the A2780 ovarian cancer cell line.