Bioactive tetrahydrofuran lignans from Peperomia dindygulensis

Anti-trypanosomal Lignans Isolated from Salvadoran Peperomia pseudopereskiifolia

A search for anti-trypanosomal natural compounds from plants collected in El Salvador, a country particularly endemic for Chagas disease, resulted in the isolation of five lignan-type compounds (1-5) from Peperomia pseudopereskiifolia. The lignan derivatives 1, 2, and 4 are new. Their absolute configuration was determined by chemical derivatization. Compounds 1, 5, 6, and 8 exhibited anti-trypanosomal activity against the amastigote form of T. cruzi comparable to that of the existing drug benznidazole.

Cannabinoid-like meroterpenoids from Peperomia incana

Ten previously undescribed metabolites were isolated from Peperomia incana (Haw.) A. Dietr. (Piperaceae), among which four contained a chromene moiety, two were identified as meroterpene lactones, and four were cannabinoid-like compounds. While the chemical structures of the compounds were assigned based on HRESIMS and 1D and 2D-NMR spectra analyses, the relative and absolute configurations were assigned from NOE correlations and a combination of ECD data and X-ray single crystal analyses, respectively. In a cytotoxic assay against a panel of seven human cancer cell lines (A549, MDA-MB-231, HeLa, DU 145, 5637, Hep G2, and MIA PaCa-2, which represent non-small cell lung cancer, as well as breast, cervical, prostate, bladder, liver, and pancreas carcinomas, respectively) most of the isolated compounds showed promising cytotoxic activities. The incanachromenes B, and incanabinoids A and C exhibited the highest cytotoxicity toward all tested cancer cell lines with IC₅₀ values in the range of 5.0-10.0 μM, whereas incanolides A, B, and incanabinoid B showed the lowest cytotoxic activity. In addition, incanachromene C and incanabinoid C produced a significant antibacterial effect toward planktonic cells and biofilms of multidrug-resistant Staphylococcus aureus strains.

Synthesis and Activity of 2-Acyl-cyclohexane-1,3-dione Congeners Derived from Peperomia Natural Products against the Plant p-Hydroxyphenylpyruvate Dioxygenase Herbicidal Molecular Target Site

Plastoquinone is a key electron carrier in photosynthesis and an essential cofactor for the biosynthesis of carotenoids. p-Hydroxyphenylpyruvate dioxygenase (HPPD) is a vital enzymatic step in plastoquinone biosynthesis that is the target of triketone herbicides, such as those derived from the pharmacophore backbone of the natural product leptospermone. In this work, the inhibitory activity of a series of 2-acyl-cyclohexane-1,3-diones congeners derived from Peperomia natural products was tested on plant HPPD. The most active compound was a 2-acyl-cyclohexane-1,3-dione with a C₁₁ alkyl side chain (5d; I₅₀app: 0.18 ± 0.02 μM) that was slightly more potent than the commercial triketone herbicide sulcotrione (I₅₀app: 0.25 ± 0.02 μM). QSAR analysis and docking studies were performed to further characterize the key structural features imparting activity. A 1,3-dione feature was required for inhibition of HPPD. Molecules with a side chain of 11 carbons were found to be optimal for inhibition, while the presence of a double bond, hydroxy, or methyl beyond the required structural features on the cyclohexane ring generally decreased HPPD inhibiting activity.

Bioactive Phenolic Compounds from Peperomia obtusifolia

Peperomia obtusifolia (L.) A. Dietr., native to Middle America, is an ornamental plant also traditionally used for its mild antimicrobial properties. Chemical investigation on the leaves of P. obtusifolia resulted in the isolation of two previously undescribed compounds, named peperomic ester (1) and peperoside (2), together with five known compounds, viz. N-[2-(3,4-dihydroxyphenyl)ethyl]-3,4-dihydroxybenzamide (3), becatamide (4), peperobtusin A (5), peperomin B (6), and arabinothalictoside (7). The structures of these compounds were elucidated by 1D and 2D NMR techniques and HREIMS analyses. Compounds 1–7 were evaluated for their anthelmintic (against Caenorhabditis elegans), antifungal (against Botrytis cinerea, Septoria tritici and Phytophthora infestans), antibacterial (against Bacillus subtilis and Aliivibrio fischeri), and antiproliferative (against PC-3 and HT-29 human cancer cell lines) activities. The known peperobtusin A (5) was the most active compound against the PC-3 cancer cell line with IC₅₀ values of 25.6 µM and 36.0 µM in MTT and CV assays, respectively. This compound also induced 90% inhibition of bacterial growth of the Gram-positive B. subtilis at a concentration of 100 µM. In addition, compound 3 showed anti-oomycotic activity against P. infestans with an inhibition value of 56% by using a concentration of 125 µM. However, no anthelmintic activity was observed.

Chemical Composition of Leaves, Stem, and Roots of Peperomia pellucida (L.) Kunth

Peperomia pellucida is a species known in the Amazon as “erva-de-jabuti” that has been used in several therapeutic applications based on folk medicine. Herein, we describe the classes, subclasses, and the main compounds of the leaves, stems, and roots from P. pellucida by ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry associated with molecular networks, mirror plot on the GNPS library, and machine learning. These data show compounds that were annotated for the first time in the Peperomia genus, such as 2′,4′,5′-trihydroxybutyrophenonevelutin, dehydroretrofractamide C, and retrofractamide B.

Hypervalent-iodine promoted selective cleavage of C(sp3)–C(sp3) bonds in ethers

A visible-light-promoted and radical-mediated strategy for the site-specific cleavage of C(sp3)–C(sp3) bonds in ethers is reported.

Metal-free visible-light-promoted C(sp3)-H functionalization of aliphatic cyclic ethers using trace O2

Presented is a light-promoted C-C bond forming reaction yielding sulfone and phosphate derivatives at room temperature in the absence of metals or photoredox catalyst. This transformation proceeds in neat conditions through an auto-oxidation mechanism which is maintained through the leaching of trace amounts of O2 as sole green oxidant.

Anti-inflammatory, ulcerogenic and platelet activation evaluation of novel 1,4-diaryl-1,2,3-triazole neolignan-celecoxib hybrids

This study reports the synthesis of novel neolignans-celecoxib hybrids and the evaluation of their biological activity. Analogs8-13(L13-L18) exhibited anti-inflammatory activity, inhibited glycoprotein expression (P-selectin) related to platelet activation, and were considered non- ulcerogenic in the animal model, even with the administration of 10 times higher than the dose used in reference therapy. In silico drug-likeness showed that the analogs are compliant with Lipinski's rule of five. A molecular docking study showed that the hybrids8-13(L13-L18) fitted similarly with celecoxib in the COX-2 active site. According to this data, it is possible to infer that extra hydrophobic interactions and the hydrogen interactions with the triazole core may improve the selectivity towards the COX-2 active site. Furthermore, the molecular docking study with P-selectin showed the binding affinity of the analogs in the active site, performing important interactions with amino acid residues such as Tyr 48. Whereas the P-selectin is a promising target to the design of new anti-inflammatory drugs with antithrombotic properties, a distinct butterfly-like structure of 1,4-diaryl-1,2,3-triazole neolignan-celecoxib hybrids synthesized in this work may be a safer alternative to the traditional COX-2 inhibitors.

Bioactive tetrahydrofuran lignans from roots, stems, leaves and twigs of Anogeissus rivularis

Four previously undescribed tetrahydrofuran lignans, named anorisols A-D (1-4) and fourteen known compounds (5-18) were isolated from the roots, stems, leaves and twigs of Anogeissus rivularis. The chemical structures were elucidated on the basis of their spectroscopic data and by comparison with the literature data. The absolute configurations of 1-4 were established by comparison of the experimental ECD spectra with the calculated ECD spectra. Some isolated compounds were evaluated for their cytotoxic activity as well as anti-HIV-1 activity employing reverse transcriptase (RT) and syncytium reduction assays using the ^ΔTat/RevMC99 virus in 1A2 cell line systems. Compound 6 displayed the most potent activity in syncytium inhibition assay with effective concentration at 50% (EC₅₀) value of 13.3 μM (SI >3.0). In the reverse transcriptase assay, compound 1 exhibited moderate activity with IC₅₀ value of 213.9 μM.

Biosynthesis of Pellucidin A in Peperomia pellucida (L.) HBK

Peperomia pellucida (L.) HBK (Piperaceae) ("jabuti herb") is an herbaceous plant that is widespread in the tropics and has several ethnomedicinal uses. The phytochemical study of leaf extracts resulted in the isolation of 2,4,5-trimethoxycinnamic acid, 5,6,7-trimethoxyflavone, 2,4,5-trimethoxystyrene, 2,4,5-trimethoxybenzaldehyde, dillapiol, and sesamin in addition to pellucidin A. The co-occurrence of styrene and cyclobutane dimers suggested the formation of pellucidin A by a photochemical [2+2] cycloaddition of two molecules of 2,4,5-trimethoxystyrene. To investigate this biogenesis, analysis of plant leaves throughout ontogeny and treatments such as drought, herbivory and, exposure to jasmonic acid and UV365 light were carried out. Significant increases in the content of dillapiol (up to 86.0%) were found when P. pellucida plants were treated with jasmonic acid, whereas treatment under UV365 light increase the pellucidin A content (193.2%). The biosynthetic hypothesis was examined by feeding various 13C-labeled precursors, followed by analysis with GC-MS, which showed incorporation of L-(2-13C)-phenylalanine (0.72%), (8-13C)-cinnamic acid (1.32%), (8-13C)-ferulic acid (0.51%), (8-13C)-2,4,5-trimethoxycinnamic acid (7.5%), and (8-13C)-2,4,5-trimethoxystyrene (12.8%) into pellucidin A. The enzymatic conversion assays indicated decarboxylation of 2,4,5-trimethoxycinnamic acid into 2,4,5-trimethoxystyrene, which was subsequently dimerized into pellucidin A under UV light. Taken together, the biosynthesis of pellucidin A in P. pellucida involves a sequence of reactions starting with L-phenylalanine, cinnamic acid, ferulic acid, 2,4,5-trimethoxycinnamic acid, which then decarboxylates to form 2,4,5-trimethoxystyrene and then is photochemically dimerized to produce pellucidin A.

Chemistry and Neurotrophic Activities of (-)-Talaumidin and Its Derivatives

(–)-Talaumidin (1), a 2,5-biaryl-3,4-dimethyltetrahydrofuran lignan isolated from Aristolochia arcuata Masters, exhibits significant neurite-outgrowth promotion and neuroprotection in primary cultured rat cortical neurons and in NGF-differentiated PC12 cells. The first enantioselective total synthesis of 1 was achieved by a flexible and reliable synthetic pathway involving an Evans asymmetric aldol reaction, as well as a stereocontrolled hydroboration and Friedel–Crafts arylation, to construct the four contiguous chiral centers on the tetrahydrofuran (THF) ring of 1. In order to investigate the stereochemistry–activity relationship of 1, a systematic synthesis of all diastereomers of 1 was accomplished by applying the synthetic strategy used for natural product 1. The evaluation of neurite-outgrowth promotion by all of the synthesized diastereomers indicated that the (–)-(1S,2R,3S,4R)-isomer 1e was significantly more active than naturally occurring 1. Additionally, we established a synthetic methodology for talaumidin derivatives that could be used to prepare a variety of analogs in a few steps and on a large scale. The synthesized racemic analog rac-1e (56a) exhibited neurite-outgrowth promoting activity in NGF-differentiated PC12 cells to the same degree as the optically active (–)-1e, revealing that a relative configuration bearing all-cis- substituents is important for potent neurotrophic activity, whilst the absolute configuration does not affect activity. Fourteen analogs based on (±)-56a were prepared via the same synthetic methodology. Among them, 56b with a methylenedioxy group on both benzene rings was found to exhibit the most significant neurite outgrowth promotion. In addition, 56a and 56b induced regeneration of the mouse optic nerve in vivo, and their activity was higher than that of talaumidin, as well as their in vitro measured activity. Furthermore, the structure–activity relationship of 56b indicated that the two benzene rings were essential structures, and that the methyl groups on the THF ring could enhance the neurotrophic activity. This result suggests that the two benzene rings of the talaumidin derivatives are essential structures for neurotrophic activity, while the two methyl groups on the THF ring can enhance neurite-outgrowth activity. Finally, it was observed that 1 and derivatives 56a and 56b exhibited potent regenerative activity in the injured mouse optic nerve in vivo.

Bioassay-Guided Isolation and in Silico Study of Antibacterial Compounds From Petroleum Ether Extract of Peperomia blanda (Jacq.) Kunth

Bioassay-guided isolation protocol was performed on petroleum ether extract of Peperomia blanda (Jacq.) Kunth using column chromatographic techniques. Five compounds were isolated and their structures were elucidated via one-dimensional (1D) and two-dimensional (2D) NMR, gas chromatography mass sectroscopy (GCMS), liquid chromatography mass spectroscopy (LCMS), and ultraviolet (UV) and infrared (IR) analyses. Dindygulerione E (a new compound), and two compounds isolated from P. blanda for the first time-namely, dindygulerione A and flavokawain A-are reported herein. Antimicrobial activity was screened against selected pathogenic microbes, and minimum inhibitory concentrations (MIC) were recorded within the range of 62-250 μg/mL. Assessment of the pharmacotherapeutic potential has also been done for the isolated compounds, using the Prediction of Activity spectra for Substances (PASS) software, and different activities of compounds were predicted. Molecular docking, molecular dynamics simulation and molecular mechanics/Poisson-Boltzmann Surface Area (MM-PBSA) calculations have proposed the binding affinity of these compounds toward methylthioadenosine phosphorylase enzyme, which may explain their inhibitory actions.

The Anti-Proliferation, Cycle Arrest and Apoptotic Inducing Activity of Peperomin E on Prostate Cancer PC-3 Cell Line

Peperomin E is a natural secolignan existing distributed in the plants of the genus Peperomia. Previous investigations demonstrated that peperomin E showed potential antitumor activity in some cancer lines, but it is unclear whether peperomin E has an effect on prostate cancer cell lines. The aim of the present study is to investigate its effects on proliferation inhibition, apoptosis-inducing and cell-cycle arrest activity using a prostate cancer PC-3 cell line. The proliferation inhibition was evaluated by MTT assay, apoptosis was detected by Annexin V/propidium iodide (PI) staining and Hoechst 33258 staining, cell cycle distributions were measured by flow cytometry, and western blot analysis was used to determine specific cellular apoptotic protein expressions of Bcl-2, Bax, caspase-3 and cleaved-caspase-3. According to the results of this study, peperomin E exhibited significant anti-proliferation activity on PC-3 cell lines in vitro in a dose-dependent manner. Peperomin E treatments lead to marked morphological changes. Apoptotic cell count and cell-cycle distribution at G2/M phase significantly increased with increasing concentrations of peperomin E. The down-regulated expression level of Bcl-2 and up-regulated expression level of Bax and cleaved-caspase-3 compared with the controls were also observed after peperomin E treatment. These data suggest that peperomin E exhibited proliferation inhabitation, apoptosis-inducing and cell-cycle arrest activity on PC-3 cell lines. The anti-proliferation effect of peperomin E on PC-3 cells should result partly from its cell-cycle arrest and apoptosis-inducing activity, whereas the increasing of the Bax/Bcl-2 ratio and activation of caspases-3 play an important role in the development of apoptosis.

Peperomin E (PepE) protects against high fat diet-induced atherosclerosis in Apolipoprotein E deficient (ApoE-/-) mice through reducing inflammation via the suppression of NLRP3 signaling pathway

Peperomin E (PepE) is a type of secolignan, a major component of the plant Peperomia dindygulensis. It has been shown to exert anti-inflammatory effects; however, the effects of PepE on human atherosclerosis remain unexplored. In the study, we investigated the role of PepE in high fat diet (HFD) induced atherosclerosis using apolipoprotein E defcient (ApoE^-/-) mice. Elevated serum homocyteine, cholesterol, and triglyceride levels, accelerated progression of atherosclerosis and exacerbated macrophage infiltration into atherosclerotic lesions were observed in HFD-fed ApoE^-/- mice, which were attenuated by PepE treatment. ApoE^-/- mice fed with HFD exhibited significantly high levels of inflammation-associated regulators in artery tissues, accompanied with an increased expression of p-inhibitor of κBα (IκBα) and p-nuclear factor-kappa B (NF-κB), and the process was blocked by PepE administration. Further, we found NOD-like receptor pyrin 3 (NLRP3) inflammasome activation in artery tissues of HFD-fed ApoE^-/- mice. In vitro, silencing NLRP3 using small interfering RNA efficiently inhibited oxidized-low-density lipoprotein (oxLDL)-induced ASC and Caspase-1 expressions, interleukin (IL)-1β and IL-18 production in human aortic endothelial cells (HAECs). Further experiments indicated that NLRP3-ASC pathway was activated by reactive oxygen species (ROS), since ROS scavenger of N-acetyl-cysteine (NAC) prevented, which was further reduced by PepE addition. However, the anti-inflammatory effects of PepE on oxLDL-incubated HAECs were abolished by over-expression NLRP3. Together, our study revealed that PepE inhibited atherosclerosis development in HFD-fed ApoE^-/- mice by suppressing NLRP3 inflammatory signaling pathway, and suggested that PepE might be a potential therapeutic strategy in the prevention of atherosclerosis.

Configuration and stability of naturally occurring all-cis-tetrahydrofuran lignans from Piper solmsianum

First occurrence of all-cishexamethoxy-tetrahydrofuran lignans1aand1b, which are 6.5 kcal mol⁻¹less stable than the all-transisomer grandisin (2a).

Peperomin E reactivates silenced tumor suppressor genes in lung cancer cells by inhibition of DNA methyltransferase

Advanced lung cancer has poor prognosis owing to its low sensitivity to current chemotherapy agents. Therefore, discovery of new therapeutic agents is urgently needed. In this study, we investigated the antitumor effects of peperomin E, a secolignan isolated from Peperomia dindygulensis, a frequently used Chinese folk medicine for lung cancer treatment. The results indicate that peperomin E has antiproliferative effects, promoting apoptosis and cell cycle arrest in non‐small‐cell lung cancer (NSCLC) cell lines in a dose‐dependent manner, while showing lower toxicity against normal human lung epidermal cells. Peperomin E inhibited tumor growth in A549 xenograft BALB/c nude mice without significant secondary adverse effects, indicating that it may be safely used to treat NSCLC. Furthermore, the mechanisms underlying the anticancer effects of peperomin E have been investigated. Using an in silico target fishing method, we observed that peperomin E directly interacts with the active domain of DNA methyltransferase 1 (DNMT1), potentially affecting its genome methylation activity. Subsequent experiments verified that peperomin E decreased DNMT1 activity and expression, thereby decreasing global methylation and reactivating the epigenetically silenced tumor suppressor genes including RASSF1A,APC,RUNX3, and p16INK4, which in turn activates their mediated pro‐apoptotic and cell cycle regulatory signaling pathways in lung cancer cells. The observations herein report for the first time that peperomin E is a potential chemotherapeutic agent for NSCLC. The anticancer effects of peperomin E may be partly attributable to its ability to demethylate and reactivate methylation‐silenced tumor suppressor genes through direct inhibition of the activity and expression of DNMT1.

The natural secolignan peperomin E induces apoptosis of human gastric carcinoma cells via the mitochondrial and PI3K/Akt signaling pathways in vitro and in vivo

BACKGROUND

Peperomin E (PepE) is a type of secolignan that is a major component of the plant Peperomia dindygulensis. It has been shown to exert anticancer effects in various cancer cell lines; however, the effects of PepE on human gastric cancer remain unexplored.

PURPOSE

The aim of this study was to investigate the effectiveness of PepE as a treatment of gastric cancer and to identify the underlying mechanisms of its anticancer activity.

STUDY DESIGN

The efficacy of PepE was examined using human gastric carcinoma SGC-7901, BGC-823, MKN-45 cell lines and normal gastric epithelial GES-1 cell line as an in vitro model and SGC-7901 xenograft mice as an in vivo model.

METHODS

Cell viability assays were used to examine the anticancer effect of 0-204.8µM concentrations of PepE in vitro. Additionally, flow cytometry and western blotting were used to elucidate the mechanism with a particular focus on apoptosis. SGC-7901 cells were injected into BALB/c mice, which were then treated with 5 or 15mg/kg/day dose of PepE. The in vivo activity of PepE was investigated by measuring tumors and conducting immunohistochemistry experiments. The safety of PepE was investigated by measuring blood biochemical parameters and conducting histopathological analysis. Taxol was used throughout as a positive control.

RESULTS

The results showed that PepE exhibited antiproliferative effects against gastric cancer cells and induced their apoptosis in a dose dependent manner with lower toxicity against normal gastric epithelial cells. Mechanistic evaluations indicated that PepE induced apoptosis by reducing the mitochondrial membrane potential (MTP), inducing cytochrome C release from mitochondria, reducing the ratio of Bcl-2/Bax and Bcl-xl/Bad, increasing activation of caspase-3, and decreasing the levels of PI3K and pAkt. The apoptotic effect of PepE on SGC-7901 cells was partially blocked by an Akt activator SC79. PepE potently inhibited in vivo tumor growth with no obvious toxicity following subcutaneous inoculation of SGC-7901 cells in nude mice.

CONCLUSIONS

These findings indicate that PepE can inhibit cell proliferation and induce apoptosis of gastric cancer cells through mitochondrial and PI3K/Akt signaling pathways with relative safety and may be a novel effective chemotherapeutic agent against gastric cancer.

New lignans and their biological activities

Lignans, which are widely distributed in higher plants, represent a vast and rather diverse group of phenylpropane derivatives. They have attracted considerable attention due to their pharmacological activities. Some of the lignans have been developed approved therapeutics, and others are considered as lead structures for new drugs. This article is based on our previous review of lignans discovered in the period 2000-2004, and it provides a comprehensive compilation of the 354 new naturally occurring lignans obtained from 61 plant families between 2005 and 2011. We classified five main types according to their structural features, and provided the details of their sources, some typical structures, and diverse biological activities. A tabular compilation of the novel lignans by species is presented at the end. A total of 144 references were considered for this review.

Antifungal and cytotoxic 2-acylcyclohexane-1,3-diones from Peperomia alata and P. trineura

Bioactivity-guided fractionation of the separate CH2Cl2 extracts from the aerial parts of Peperomia alata and P. trineura yielded seven polyketides: alatanone A [3-hydroxy-2-(5'-phenylpent-4'E-enoyl)cyclohex-2-en-1-one, 1a] and alatanone B [3-hydroxy-2-(3'-phenyl-6'-methylenedioxypropanoyl)cyclohex-2-en-1-one, 2a] from P. alata and trineurone A [3-hydroxy-2-(11'-phenylundec-10'E-enoyl)cyclohex-2-en-1-one, 1b], trineurone B [3-hydroxy-2-(15'-phenyl-18'-methylenedioxypentadecanoyl)cyclohex-2-en-1-one, 2b], trineurone C [3-hydroxy-2-(17'-phenyl-20'-methylenedioxyheptadecanoyl)cyclohex-2-en-1-one, 2c], trineurone D [3-hydroxy-2-(hexadec-10'Z-enoyl)cyclohex-2-en-1-one, 3a], and trineurone E [(6R)-(+)-3,6-dihydroxy-2-(hexadec-10'Z-enoyl)cyclohex-2-en-1-one, 3b] from P. trineura. The isolated compounds were evaluated for antifungal activity against Cladosporium cladosporioides and C. sphaeospermum and for cytotoxicity against the K562 and Nalm-6 leukemia cell lines.

Antiangiogenic polyketides from Peperomia dindygulensis Miq

Two new polyketides: 2Z-(heptadec-12-enyl)-4-hydroxy-3,4,7,8-tetrahydro-2H-chromen-5(6H)-one (1) and 2-(heptadec-12-enyl)-5-hydroxy-5,6,7,8-tetrahydrochromen- 4-one (2), together with eleven known compounds: 4-hydroxy-2-[(3,4-methylenedioxy- phenyl)tridecanoyl] cyclohexane-1,3-dione (3), oleiferinone (4), 4-hydroxy-2-[(3,4- methylenedioxyphenyl)undecanoyl]cyclohexane-1,3-dione (5), 4-hydroxy-2-[(11-phenyl- undecanoyl)cyclohexane-1,3-dione (6), proctorione C (7), surinone C (8), 5-hydroxy- 7,8,4'-trimethoxyflavone (9), 5-hydroxy-7,8,3',4'-tetramethoxyflavone (10), 5-hydroxy- 7,3',4'-trimethoxyflavone (11), 5,8-dihydroxy-7,3',4'-trimethoxyflavone (12) and cepharanone B (13) were isolated from the whole plant of Peperomia dindygulensis Miq. Their structures were elucidated by spectroscopic methods, including 2D-NMR techniques. Compounds 2, 3, 5 and 8 inhibited human umbilical vein endothelial cell (HUVEC) proliferation and compounds 5 and 8 sharply suppressed HUVEC tube formation.

Microbial transformations of aryltetralone and aryltetralin lignans by Cunninghamella echinulata and Beauveria bassiana

Microbiological transformation of the aryltetralone lignan (-)-8'-epi-aristoligone (1) with Cunninghamella echinulata ATCC 10028B afforded two known natural lignans, (-)-holostyligone (3) and (-)-arisantetralone (4). Incubation of the aryltetralin lignan (-)-isogalbulin (2), obtained by chemical transformation of 1, with C. echinulata ATCC 10028B afforded the known lignan aryltetralol (5) and seven new metabolites, (-)-8-hydroxyisogalbulin (6), (-)-7-methoxyisogalbulin (7), (-)-4'-O-demethyl-8-hydroxyisogalbulin (8), (-)-7-methoxy-8-hydroxyisogalbulin (9), (-)-4'-O-demethyl-7-methoxyisogalbulin (10), (-)-4',5-O-didemethylcyclogalgravin (11), and (-)-4'-O-demethylcyclogalgravin (12). When 2 was subjected to biotransformation with Beauveria bassiana ATCC 7159, (-)-8-hydroxyisogalbulin (6) was the only isolable product. The structures of all new compounds were established by detailed analysis of their spectroscopic data.

Bioactive triterpene saponins from the roots of Phytolacca americana

Five new triterpene saponins named phytolaccasaponins N-1 (1), N-2 (2), N-3 (3) N-4 (4), and N-5 (5) were isolated from the roots of Phytolacca americana together with seven known triterpene saponins (6-12). The structures of the five new saponins were established as shown in structures 1-5 on the basis of their spectroscopic data. The MDR-reversal activity of 1-12 was evaluated on the basis of the amount of calcein accumulated in MDR human ovarian cancer 2780 AD cells in the presence of each compound. The most effective compound was 8 (155% of control at 25 microg/mL).

A synthetic entry to pladienolide B and FD-895

Presented within are syntheses of the pladienolide B and FD-895 side-chains, as well as models of the essential ring-closing metathesis and Stille coupling that will be used to complete their total syntheses. Several analogs of the pladienolide B side-chain were also prepared in order to evaluate the scope of the methodology and to create a library of structures that could be used for stereochemical and SAR analyses.

Chemistry and evolution of the Piperaceae

The chemistry of members of the family Piperaceae is of great interest owing to the variety of biological properties displayed. A survey of structural diversity and bioactivity reveals that groups of species specialize in the production of amides, phenylpropanoids, lignans and neolignans, benzoic acids and chromenes, alkaloids, polyketides, and a plethora of compounds of mixed biosynthetic origin. Bioassays againstCladosporium cladosporioidesandC. sphaerospermunhave resulted in the characterization of various amides, prenylated phenolic compounds, and polyketides as potential classes of antifungal agents. Studies on the developmental process in seedlings ofPiper solmsianumhave shown that phenylpropanoid are produced instead of the tetrahydrofuran lignans found in adult plants. In suspension cultures ofP. cernuumandP. crassinervium, phenylethylamines and alkamides predominate, whereas in the adult plants prenylpropanoids and prenylated benzoic acids are the respective major compound classes. Knowledge of the chemistry, bioactivity, and ecology of Piperaceae species provides preliminary clues for an overall interpretation of the possible role and occurrence of major classes of compounds.

Stereoselective synthesis of highly O-functionalized enantiopure 2,3,4-trisubstituted tetrahydrofurans by tandem debenzylative cyclization of glycal derived 2,3-epoxy alcohols

A new and highly efficient methodology for the construction of synthetically important highly O-functionalized enantiopure 2,3,4-trisubstituted tetrahydrofurans with three contiguous stereocenters is reported.