Cytotoxic and NF-κB inhibitory sesquiterpene lactones from Piptocoma rufescens

Strategies for the discovery of potential anticancer agents from plants collected from Southeast Asian tropical rainforests as a case study

Covering up to early 2023The present review summarizes recent accomplishments made as part of a multidisciplinary, multi-institutional anticancer drug discovery project, wherein samples comprising higher plants were collected primarily from Southeast Asia, and also from Central America, and the West Indies. In the introductory paragraphs, a short perspective is provided on the current importance of plants in the discovery of cancer therapeutic agents, and the contributions of other groups working towards this objective are mentioned. For our own investigations, following their collection, tropical plants have been subjected to solvent extraction and biological evaluation for their antitumor potential. Several examples of purified plant lead bioactive compounds were obtained and characterized, and found to exhibit diverse structures, including those of the alkaloid, cardiac glycoside, coumarin, cucurbitacin, cyclobenzofuran (rocaglate), flavonoid, lignan, and terpenoid types. In order to maximize the efficiency of work on drug discovery from tropical plant species, strategies to optimize various research components have been developed, including those for the plant collections and taxonomic identification, in accordance with the requirements of contemporary international treaties and with a focus on species conservation. A major component of this aspect of the work is the development of collaborative research agreements with representatives of the source countries of tropical rainforest plants. The phytochemical aspects have included the preparation of plant extracts for initial screening and the selection of promising extracts for activity-guided fractionation. In an attempt to facilitate this process, a TOCSY-based NMR procedure has been applied for the determination of bioactive rocaglate derivatives in samples of Aglaia species (Meliaceae) collected for the project. Preliminary in vitro and in vivo mechanistic studies carried out by the authors are described for two tropical plant-derived bioactive lead compounds, corchorusoside C and (+)-betulin, including work conducted with a zebrafish (Danio rerio) model. In the concluding remarks, a number of lessons are summarized that our group has learned as a result of working on anticancer drug discovery using tropical plants, which we hope will be of interest to future workers.

Digital Database of Absorption Spectra of Diverse Flavonoids Enables Structural Comparisons and Quantitative Evaluations

Flavonoids play diverse roles in plants, comprise a non-negligible fraction of net primary photosynthetic production, and impart beneficial effects in human health from a plant-based diet. Absorption spectroscopy is an essential tool for quantitation of flavonoids isolated from complex plant extracts. The absorption spectra of flavonoids typically consist of two major bands, band I (300-380 nm) and band II (240-295 nm), where the former engenders a yellow color; in some flavonoids the absorption tails to 400-450 nm. The absorption spectra of 177 flavonoids and analogues of natural or synthetic origin have been assembled, including molar absorption coefficients (109 from the literature, 68 measured here). The spectral data are in digital form and can be viewed and accessed at http://www.photochemcad.com. The database enables comparison of the absorption spectral features of 12 distinct types of flavonoids including flavan-3-ols (e.g., catechin, epigallocatechin), flavanones (e.g., hesperidin, naringin), 3-hydroxyflavanones (e.g., taxifolin, silybin), isoflavones (e.g., daidzein, genistein), flavones (e.g., diosmin, luteolin), and flavonols (e.g., fisetin, myricetin). The structural features that give rise to shifts in wavelength and intensity are delineated. The availability of digital absorption spectra for diverse flavonoids facilitates analysis and quantitation of these valuable plant secondary metabolites. Four examples are provided of calculations─multicomponent analysis, solar ultraviolet photoprotection, sun protection factor (SPF), and Förster resonance energy transfer (FRET)─for which the spectra and accompanying molar absorption coefficients are sine qua non.

Potential of natural phenolic antioxidant compounds from Bersama abyssinica (Meliathacea) for treatment of chronic diseases

Chronic diseases including cardiovascular, diabetes and cancer persist for a long time in the course of treatment affecting health and are currently the cause of many deaths. In most cases, the treatment of chronic infectious diseases especially Tuberculosis relies on conventional drugs which are currently becoming fruitless due to drug resistance and unpredicted complications in course of treatment. However, herbal medicines have for a long time been used in prevention and treatment of chronic diseases including asthma and heart diseases in Africa. In this study, we extracted metabolites and screened for active compounds with potential free radical scavenging and pharmacological activities from Bersama abyssinica, the plant commonly used in traditional medicine in Tanzania. B. abyssinica root, stembark and leaf were air dried, sequentially extracted in various solvents including petroleum ether, dichloromethane, ethylacetate and methanol to yield extracts and fractions. The extracts and fractions were tested for the presence of several metabolites and antioxidant activity. The analysis of chemical compounds from resultant extracts was done by GC–MS for non-polar factions and LC-MS/MC for moderate polar extracts.High amount of phenolic acid, flavonoids and tannin were identified in ethylacetate fraction compared to ethanol, dichloromethane and petroleum ether. The GC–MS analysis of petroleum ether extract of B. abyssinica stem back yielded twelve (12) compounds with varying composition. The most abundant compounds were 2-Butenoic acid, 3-methyl-, ethyl ester comprising 33.8%, n-Hexadecanoic acid comprising 16.7% and Ethanolpentamethyl- yielded in 16.7%.The LC-MS/MS analysis of Ethyl acetate fractions yielded 20 compounds including; Mangiferin and Isoquercitin were abundant in leaves, stembark and roots. Lastly, ethyl vanillate was identified in both roots and leaves whereas Quercitrin and 7,8-Dimethoxycoumarin were found in stembark and root.These findings indicated that B. abyssinica is rich in phenolic compounds ranging from phenolic acids, flavonoids and coumarin that possess high antioxidant and pharmacological properties potential for treatment of chronic diseases.

New Techniques of Structure Elucidation for Sesquiterpenes

The most significant new techniques that have been used in the twenty-first century for the structure elucidation of sesquiterpenes and some derivatives are reviewed in this chapter. A distinctive feature of these methodologies is the combination of accurate experimental measurements with theoretical data obtained by molecular modeling calculations that allow to visualize, understand, and quantify many structural characteristics. This has been the case for NMR spectroscopy, which has expanded its potential for solving complex structural problems by means of comparison with quantum mechanical molecular models. Ab initio and density functional theory calculations of chemical shifts, coupling constants, and residual chemical shift anisotropies have played important roles in the solution of many structures of sesquiterpenes. The assignments of their absolute configurations by evaluation of calculated and experimental chiroptical properties as electronic and vibrational circular dichroism are also reviewed. This chapter also includes the use of X-ray diffraction analysis with emphasis on calculations of the Flack and Hooft parameters, which are applicable to all molecules that crystallize in non-centrosymmetric space groups. The accurate molecular models of sesquiterpenes, validated by concordance with their experimental properties, are nowadays essential for the interpretation of the effects of these natural products on biological systems.

Development of Potential Antitumor Agents from the Scaffolds of Plant-Derived Terpenoid Lactones

Naturally occurring terpenoid lactones and their synthetic derivatives have attracted increasing interest for their promising antitumor activity and potential utilization in the discovery and design of new antitumor agents. In the present perspective article, selected plant-derived five-membered γ-lactones and six-membered δ-lactones that occur with terpenoid scaffolds are reviewed, with their structures, cancer cell line cytotoxicity and in vivo antitumor activity, structure-activity relationships, mechanism of action, and the potential for developing cancer chemotherapeutic agents discussed in each case. The compounds presented include artemisinin (ART, 1), parthenolide (PTL, 2), thapsigargin (TPG, 3), andrographolide (AGL, 4), ginkgolide B (GKL B, 5), jolkinolide B (JKL B, 6), nagilactone E (NGL E, 7), triptolide (TPL, 8), bruceantin (BRC, 9), dichapetalin A (DCT A, 10), and limonin (LMN, 11), and their naturally occurring analogues and synthetic derivatives. It is hoped that this contribution will be supportive of the future development of additional efficacious anticancer agents derived from natural products.

Molecular Simulation Elaborating the Mechanism of 1β-Hydroxy Alantolactone Inhibiting Ubiquitin-Conjugating Enzyme UbcH5s

1β-hydroxy alantolactone, a sesquiterpene lactone, exhibits potent anti-inflammatory and anticancer activities. Recently, it has been found to target UbcH5s by covalently bonding with Cys85 specifically, but the exact molecular basis remains unclear. Here, we analyzed the structural specificity of the catalytic site of UbcH5s by comparing them with other E2 proteins. Molecular dynamics was performed to detect the structural stability of the catalytic site. Docking method was then used to predict conformations of ligand docked at the catalytic site of UbcH5s. The electrostatic surface and charge distribution of ligand and proteins were analyzed by quantitative calculation. Molecular dynamics was used to detect the stability of docking complexes of 1β-hydroxy alantolactone and UbcH5s, the covalently bonded intermediates and the products. The QM/MM methodology was used to calculate the free energy barrier of hydrogen transfer and formation of covalent bond between 15-position carbon of ligand and Cys85. Results revealed that the structure of the catalytic site is stable, and 1β-hydroxy alantolactone can dock at the catalytic site with correct conformation. Molecular dynamics further demonstrates that 1β-hydroxy alantolactone can steadily combine with UbcH5s. Intermediate and product of catalytic reaction are also certified to be stable. Besides, Asp112 and Asn114 function as anchors to fix ligand, ensuring it steadily docked at catalytic site to complete covalent reaction. More importantly, we have found that Cys85 of UbcH5c is more efficient to form a covalent bond with the ligand in comparison with UbcH5a and UbcH5b. Our results successfully explained the mechanism of 1β-hydroxy alantolactone covalently bonding with UbcH5s. Such molecular mechanism may provide a better insight into the molecular development or modification for ubiquitin-related drugs.

Current status and contemporary approaches to the discovery of antitumor agents from higher plants

Higher plant constituents have afforded clinically available anticancer drugs. These include both chemically unmodified small molecules and their synthetic derivatives currently used or those in clinical trials as antineoplastic agents, and an updated summary is provided. In addition, botanical dietary supplements, exemplified by mangosteen and noni constituents, are also covered as potential cancer chemotherapeutic agents. Approaches to metabolite purification, rapid dereplication, and biological evaluation including analytical hyphenated techniques, molecular networking, and advanced cellular and animal models are discussed. Further, enhanced and targeted drug delivery systems for phytochemicals, including micelles, nanoparticles and antibody drug conjugates (ADCs) are described herein.

Natural disesquiterpenoids: an update

This review highlights the progress on the isolation, bioactivity, biogenesis and total synthesis of dimeric sesquiterpenoids since 2010.

NMR data for the hydroxyl groups detected by NOESY spectra in sesquiterpene lactones

In this article we present the correlations observed in the NOESY spectra, which provide direct and unequivocal detection of hydroxyl groups occurring in the chemical structures of three sesquiterpene lactones - a germacranolide (8α-(E)-4′-hydroxysenecioyloxy-9α-hydroxyparthenolide) and two guaianolides (cynaropicrin and desacylcynaropicrin 8α-(Z)-(4′-hydroxy-2′-methyl)butenoate). The NOESY spectra and other NMR spectra, which served for the structural determination, are also presented. The data provided in this article are associated with the research article “Phytochemical profiles of the leaves of Stizolophus balsamita and Psephellus sibiricus and their chemotaxonomic implications” Nawrot et al., 2019.

Potential Anticancer Agents Characterized from Selected Tropical Plants

Higher plants are well known for their value in affording clinically useful anticancer agents, with such compounds acting against cancer cells by a range of mechanisms of action. There remains a strong interest in the discovery and development of plant secondary metabolites as additional cancer chemotherapeutic lead compounds. In the present review, progress on the discovery of plant-derived compounds of the biflavonoid, lignan, sesquiterpene, steroid, and xanthone structural types is presented. Several potential anticancer leads of these types have been characterized from tropical plants collected in three countries as part of our ongoing collaborative multi-institutional project. Preliminary structure-activity relationships and work on in vivo testing and cellular mechanisms of action are also discussed. In addition, the relevant work reported by other groups on the same compound classes is included herein.

Crystal Structures and Human Leukemia Cell Apoptosis Inducible Activities of Parthenolide Analogues Isolated from Piptocoma rufescens

The molecular structures of three parthenolide analogues, (-)-goyazensolide (1), (-)-15-deoxygoyazensolide (2), and (-)-ereglomerulide (3), isolated from the leaves of Piptocoma rufescens in a previous study were determined by X-ray analysis, and the absolute configuration of (-)-goyazensolide (1) was confirmed crystallographically using Cu Kα radiation at low temperature. Compounds 1-3, (+)-rufesolide A (4), and commercial parthenolide were found to be growth inhibitory toward MOLM-13 and EOL-1 human acute myeloid leukemia cells using PKC412 (midostaurin) as the positive control, with 1-3 being more active than parthenolide. Also, compounds 1-4 exhibited synergistic effects when tested with PKC412, but parthenolide did not show this type of activity. At a concentration lower than 2.0 μM, both 1 and 2 induced approximately 50% of the cells to become apoptotic at a late stage of the cell cycle, but no similar apoptotic effects were observed for 3, 4, or parthenolide. Leukemia cell apoptosis was induced by these compounds through the activation of caspase-3 and the inhibition of NF-κB, as indicated by immunoblotting analysis, and compounds 1 and 2 seem to be promising leads for development as potential antileukemic agents.

The Search for Anticancer Agents from Tropical Plants

Many of the clinically used anticancer agents in Western medicine are derived from secondary metabolites found in terrestrial microbes, marine organisms, and higher plants, with additional compounds of this type being currently in clinical trials. If plants are taken specifically, it is generally agreed that the prospects of encountering enhanced small organic-molecule chemical diversity are better if tropical rather than temperate species are investigated in drug discovery efforts. Plant collection in tropical source countries requires considerable preparation and organization to conduct in a responsible manner that abides by the provisions of the 1992 Rio Convention of Biological Diversity and the 2010 Nagoya Protocol on Access to Genetic Resources. Correct taxonomic identifications and enhanced procedures for processing and documenting plant samples when collected in often difficult terrain are required. Phytochemical aspects of the work involve solvent fractionation, known compound dereplication, preliminary in vitro testing, and prioritization, leading to "activity-guided fractionation", compound structure determination, and analog development. Further evaluation of lead compounds requires solubility, formulation, preliminary pharmacokinetics, and in vivo testing in suitable models. Covering the work of the authors carried out in two sequential multidisciplinary, multi-institutional research projects, examples of very promising compounds discovered from plants acquired from Africa, Southeast Asia, the Americas, and the Caribbean region, and with potential anticancer activity will be mentioned. These include plant secondary metabolites of the diphyllin lignan, cyclopenta[b]benzofuran, triterpenoid, and tropane alkaloid types.

Screening of several biological activities induced by different sesquiterpene lactones isolated from Centaurea behen L. and Rhaponticum repens (L.) Hidalgo

This study aims to evaluate the in vitro cytotoxic, in vitro and in ovo anti-angiogenic effects and antimicrobial activity of sesquiterpene lactones (SLs) from two plants Centaurea behen and Rhaponticum repens (L.). Five SLs, including cynaropicrin (1), 4β,15-dehydro-3-dehydrosolstitialin A (2), aguerin B (3), janerin (4), cebellin E (5), and a flavone hispidulin (6) were isolated from C. behen (compounds 1-3) and R. repens (compounds 4-6). Cynaropicrin (1) and aguerin B (3) were characterised by strong cytotoxic activities against A2780 cells with IC₅₀ values of 1.15 and 1.62 μg mL^-1, respectively, comparable to that of doxorubicin (IC₅₀ = 1.17 μg mL^-1). The anti-angiogenic study showed the remarkable inhibitory effect of cynaropicrin (1) and aguerin B (3) on the proliferation and migration of HUVECs. In addition, cynaropycrin and aguerin B exhibited significant angio-inhibitory effects in CAM assay. These findings may be useful for the development of novel chemotherapeutic agents for the treatment of cancer.

Development of Anticancer Agents from Plant-Derived Sesquiterpene Lactones

Sesquiterpene lactones are of considerable interest due to their potent bioactivities, including cancer cell cytotoxicity and antineoplastic efficacy in in vivo studies. Among these compounds, artesunate, dimethylaminoparthenolide, and L12ADT peptide prodrug, a derivative of thapsigargin, are being evaluated in the current cancer clinical or preclinical trials. Based on the structures of several antitumor sesquiterpene lactones, a number of analogues showing greater potency have been either isolated as natural products or partially synthesized, and some potential anticancer agents that have emerged from this group of lead compounds have been investigated extensively. The present review focuses on artemisinin, parthenolide, thapsigargin, and their naturally occurring or synthetic analogues showing potential anticancer activity. This provides an overview of the advances in the development of these types of sesquiterpene lactones as potential anticancer agents, including their structural characterization, synthesis and synthetic modification, and antitumor potential, with the mechanism of action and structure-activity relationships also discussed. It is hoped that this will be helpful in stimulating the further interest in developing sesquiterpene lactones and their derivatives as new anticancer agents.

Discovery of Anticancer Agents of Diverse Natural Origin

Recent progress is described in an ongoing collaborative multidisciplinary research project directed towards the purification, structural characterization, chemical modification, and biological evaluation of new potential natural product anticancer agents obtained from a diverse group of organisms, comprising tropical plants, aquatic and terrestrial cyanobacteria, and filamentous fungi. Information is provided on how these organisms are collected and processed. The types of bioassays are indicated in which initial extracts, chromatographic fractions, and purified isolated compounds of these acquisitions are tested. Several promising biologically active lead compounds from each major organism class investigated are described, and these may be seen to be representative of a very wide chemical diversity.

Isolation of Bioactive Rotenoids and Isoflavonoids from the Fruits of Millettia caerulea

Three new rotenoids (1-3), two new isoflavonoids (4 and 5), and six known analogues (6-11) were isolated from an n-hexane partition of a methanol extract of the fruits of Millettia caerulea, with the structures of the new compounds elucidated by analysis of their spectroscopic data. The relative configurations of the rotenoids were determined by interpretation of their NMR spectroscopic data, and their absolute configurations were established using electronic circular dichroism spectra and specific rotation values. All compounds isolated were evaluated for their cell growth inhibitory activity against the HT-29 human colon cancer cell line, and the known compounds, (-)-3-hydroxyrotenone (6) and (-)-rotenone (7), were found to be potently active. When tested in an NF-κB inhibition assay, compound 6 showed activity. This compound, along with the new compound, (-)-caeruleanone D (1), and the known compound, ichthynone (8), exhibited K-Ras inhibitory potency. Further bioactivity studies showed that the new compounds, (-)-3-deoxycaeruleanone D (2) and (-)-3-hydroxycaeruleanone A (3), and the known compounds 8 and 11 induced quinone reductase in murine Hepa 1c1c7 cells.

New acyclic bis phenylpropanoid and neolignans, from Myristica fragrans Houtt., exhibiting PARP-1 and NF-κB inhibitory effects

The bioassay-guided fractionation of the aril of Myristica fragrans (mace spice) yielded five phenolic compounds, one new acyclic bis phenylpropanoid (1) and four previously known phenolic compounds: compounds (1) (S) 1-(3,4,5-trimethoxyphenyl)-2-(3-methoxy-5-(prop-1-yl) phenyl)-propan-1-ol, (2) benzenemethanol; α-[1-[2,6-dimethoxy-4-(2-propen-1-yl)phenoxy]ethyl]-3,4-dimethoxy-1-acetate, (3) odoratisol A, phenol, 4-[(2S,3S)-2,3-dihydro-7-methoxy-3-methyl-5-(1E)-1-propenyl-2-benzofuranyl]-2,6-dimethoxy, (4) 1,3-benzodioxate-5-methanol,α-[1-[2,6-dimethoxy-4-(2-propenyl)phenoxy]ethyl]-acetate, (5) licarin C; benzofuran,2,3-dihydro-7-methoxy-3-methyl-5-(1E)-1-yl-2-(3,4,5-trimethoxyphenyl). An NMR tube Mosher ester reaction was used in an approach to characterize and determine the assignment of the absolute configuration of the new isolated chiral alcohol (1). The PARP-1 inhibitory activity was evaluated for compound (1) (IC50=3.04μM), compound (2) (IC50=0.001μM), compound (4) (IC50=22.07μM) and compound (5) (IC50=3.11μM). Furthermore, the isolated secondary metabolites were tested for NF-κB and K-Ras inhibitory activities. When tested in the p65 assay, compounds (2) and (4) displayed potent NF-κB inhibition (IC50=1.5 nM and 3.4nM, respectively).

Absolute Configuration of (-)-Centratherin, a Sesquiterpenoid Lactone, Defined by Means of Chiroptical Spectroscopy

(-)-Centratherin is a bioactive sesquiterpenoid lactone, whose absolute configuration (AC) was not established, but has been proposed based on those of germacrane precursors. To verify this proposal, the experimental electronic circular dichroism (ECD), electronic dissymmetry factor (EDF), optical rotatory dispersion (ORD), vibrational circular dichroism (VCD), and vibrational dissymmetry factor (VDF) spectra of (-)-centratherin have been analyzed with the corresponding density functional theoretical predictions. These analyses suggest the AC of naturally occurring (-)-centratherin to be (6R,7R,8S,10R,2'Z).

Rapid and efficient method for the quantification of lychnopholide in rat plasma by liquid chromatography-tandem mass spectrometry for pharmacokinetic application

Lychnopholide is a sesquiterpene lactone usually obtained from Lychnophora and Eremanthus species and has pharmacological activities that include anti-inflammatory and anti-tumor. Lychnopholide isolated from Eremanthus matogrossenssis was analyzed in this study. The aims of this study were to develop and validate an analytical methodology by LC-MS/MS and to quantify lychnopholide in rat plasma. Chromatographic separation was achieved on a C18 column using isocratic elution with the mobile phase consisting of methanol and water (containing 0.1% formic acid) at a flow rate of 0.4 mL/min. The detection was performed in multiple-reaction monitoring mode using electrospray ionization in positive mode. The method validation was performed in accordance with regulatory guidelines and the results met the acceptance criteria. The linear range of detection was 10-200 ng/mL (r > 0.9961). The intra- and inter-day assay variability were <6.2 and <11.7%, respectively. The extraction recovery was approximately 63% using liquid-liquid extraction with chloroform. Lychnopholide was detected in plasma up to 60 min after intravenous administration in rats. This rapid and sensitive method for the analysis of the sesquiterpene lactone lychnopholide in rat plasma can be applied to pharmacokinetic studies of this compound. Copyright © 2016 John Wiley & Sons, Ltd.

Antiproliferative and antimalarial sesquiterpene lactones from Piptocoma antillana from Puerto Rico

Bioassay-directed fractionation of an antiproliferative ethanol extract of the leaves and twigs of Piptocoma antillana (Asteraceae) afforded two new goyazensolide-type sesquiterpene lactones named 5-O-methyl-5-epiisogoyazensolide (1) and 15-O-methylgoyazensolide (2), together with the known compounds 1-oxo-3,10-epoxy-8-(2-methylacr1 0-epoxy-8-(2-methylacryloxy)-l 5-acetoxygermacra-2,4, 11(1 3)-trien-6(12)-olide (3) and 5-epiisogoyazensolide (4). The structure elucidation of all compounds was carried out based on NMR and mass spectroscopic data analyses. The relative and absolute configurations of all the isolated compounds were determined from their CD and NOESY NMR spectra. Compounds 1-4 showed moderately potent antiproliferative activities against A2780 ovarian cancer cells, with IC50 values of 1.5 +0.5, 0.6 ± 0.3, 1.62 ± 0.05, and 1.56 ± 0.04 μM, respectively. They also displayed antimalarial activity against Plasmodiumfalciparum, with IC50 values of 6.2 05 22 ± 0.5, 2.2± 0.5, 8.0 ± 0.4, and 9.0 ± 0.6 μM, respectively.

Antiproliferative and Antimalarial Sesquiterpene Lactones from Piptocoma antillana from Puerto Rico [1]

Bioassay-directed fractionation of an antiproliferative ethanol extract of the leaves and twigs of Piptocoma antillana (Asteraceae) afforded two new goyazensolide-type sesquiterpene lactones named 5- O-methyl-5-epiisogoyazensolide (1) and 15- O-methylgoyazensolide (2), together with the known compounds 1-oxo-3,10-epoxy-8-(2-methylacryloxy)-15-acetoxygermacra-2,4,11(13)-trien-6(12)-olide (3) and 5-epiisogoyazensolide (4). The structure elucidation of all compounds was carried out based on NMR and mass spectroscopic data analyses. The relative and absolute configurations of all the isolated compounds were determined from their CD and NOESY NMR spectra. Compounds 1–4 showed moderately potent antiproliferative activities against A2780 ovarian cancer cells, with IC50 values of 1.5 ±0.5, 0.6 ± 0.3, 1.62 ± 0.05, and 1.56 ± 0.04 μM, respectively. They also displayed antimalarial activity against Plasmodium falciparum, with IC50 values of 6.2 ± 0.5, 2.2 ± 0.5, 8.0 ± 0.4, and 9.0 ± 0.6 μM, respectively.

Gochnatia polymorpha ssp. floccosa: bioprospecting of an anti-inflammatory phytotherapy for use during pregnancy

ETHNOPHARMACOLOGICAL RELEVANCE

Gochnatia polymorpha ssp. floccosa is used in folk medicine to treat inflammation and infections. Non-steroidal anti-inflammatory drugs (NSAIDs) are the most commonly consumed medications during pregnancy in women with inflammatory diseases. However, the relationship between the use of NSAIDs and the risk of miscarriage and birth defects and/or benefits is not fully understood. Thus, an investigation regarding the use of Gochnatia polymorpha during gestation is of relevance for developing safe anti-inflammatory drugs for use during pregnancy.

MATERIALS AND METHODS

The pregnant females were randomly divided into 5 groups. Control group received a hydroalcoholic solution (1.2%), via gavage, for at least 15 days prior to mating and throughout the gestational period. The pre-treatment group received Gochnatia polymorpha ethanol extract (GPEE), via gavage, at a dose of 100mg/kg body weight (b.w.) for at least 15 days prior to mating and up to the appearance of the vaginal plug. The organogenesis group received GPEE at a dose of 100mg/kg (b.w.), via gavage, on the 5-15th gestacional day. The pregnancy group received GPEE at a dose of 100mg/kg (b.w.), via gavage, throughout the gestational period (from the 1st to the 18th day of pregnancy). The pre+pregnancy group received GPEE at a dose of 100mg/kg (b.w.), via gavage, for at least 15 days prior to mating and throughout the entire gestational period. The clinical signals of maternal toxicity and teratogenesis were evaluated. Additional assays to evaluate chronic inflammation, antigenotoxicity and immunomodolatory activity were performed.

RESULTS AND CONCLUSIONS

The results indicated that GPEE does not interfere with reproductive performance or embryo-fetal development but does correlate with reduced weight and fetal length. The extract was not teratogenic or mutagenic or an immunomodulator. However, GPEE did exhibit effective anti-inflammatory activity. Based on this study, it can be inferred that GPEE is an important, safe anti-inflammatory agent for use during pregnancy according to the experimental design we utilized, which opens up possibilities for the bioprospecting of a new anti-inflammatory phytotherapy for use during pregnancy.

Natural compounds as potential treatments of NF2-deficient schwannoma and meningioma: cucurbitacin D and goyazensolide

HYPOTHESIS

Cucurbitacin D and goyazensolide, 2 plant-derived natural compounds, possess potent growth-inhibitory activity in schwannoma and meningioma cells.

BACKGROUND

Currently, no FDA-approved drugs are available for neurofibromatosis type 2 (NF2)-associated schwannomas and meningiomas. Selected natural compounds with antineoplastic activity, such as cucurbitacin D and goyazensolide, may be developed as potential treatments for these tumors.

METHODS

The Nf2-deficient mouse schwannoma Sch10545 and human benign meningioma Ben-Men-1 cells were treated with various concentrations of cucurbitacin D and goyazensolide. The effect on cell proliferation was determined using resazurin assays. Flow cytometry was used to assess the cell cycle profiles. Western blot analysis was performed to investigate the expression of various signaling molecules related to the cell cycle and the AKT pathway.

RESULTS

Cucurbitacin D inhibited proliferation of Sch10545 cells (IC50 ∼ 0.75 μM) and Ben-Men-1 cells (IC50 ∼0.2 μM). Goyazensolide also reduced cell proliferation of Sch10545 cells (IC50 ∼0.9 μM) and Ben-Men-1 cells (IC50 ∼1 μM). The G2/M population increased in both Sch10545 and Ben-Men-1 cells treated with cucurbitacin D or goyazensolide around the IC50. Cucurbitacin and goyazensolide substantially reduced the levels of cyclins E and A in treated Sch10545 and Ben-Men-1 cells. Cucurbitacin D also inhibited cyclin B, phospho-AKT and phospho-PRAS40 expression. In addition, goyazensolide reduced the levels of phospho-AKT and NFκB and increased the expression of pro-apoptotic Bim in Sch10545 and Ben-Men-1 cells.

CONCLUSION

Both cucurbitacin D and goyazensolide effectively inhibit proliferation of NF2-deficient schwannoma and meningioma cells, suggesting that these natural compounds should be further evaluated as potential treatments for NF2-related tumors.

Constituents of an extract of Cryptocarya rubra housed in a repository with cytotoxic and glucose transport inhibitory effects

A new alkylated chalcone (1), a new 1,16-hexadecanediol diester (2), and eight known compounds were isolated from a dichloromethane-soluble repository extract of the leaves and twigs of Cryptocarya rubra collected in Hawaii. The structures of the new compounds were determined by interpretation of their spectroscopic data, and the absolute configurations of the two known cryptocaryanone-type flavonoid dimers, (+)-bicaryanone A (3) and (+)-chalcocaryanone C (4), were ascertained by analysis of their electronic circular dichroism and NOESY NMR spectra. All compounds isolated were evaluated against HT-29 human colon cancer cells, and, of these, (+)-cryptocaryone (5) was found to be potently cytotoxic toward this cancer cell line, with an IC50 value of 0.32 μM. This compound also exhibited glucose transport inhibitory activity when tested in a glucose uptake assay.

Proteomic analysis of proteins engaged in α-methylene-δ-lactone cytotoxic effects in hormone-independent breast cancer MDA-MB-231 cells

A simple synthetic α-methylene-δ-lactone, 1-isopropyl-2-methylene-1,2-dihydrobenzochromen-3-one, designated DL-3, was shown previously to induce apoptosis and significantly suppress cell metastatic potential in MDA-MB-231 breast cancer cells. The mechanisms through which DL-3 exerts its effects are poorly understood. The purpose of this study was to investigate the protein expression profiles in MDA-MB-231 cells exposed to the DL-3 treatment. Using 2D differential gel electrophoresis, a set of eight differentially expressed proteins (spot intensities which showed ≥1.25-fold change and statistical significance, p < 0.05, between the control and DL-3-treated group) were found and successfully identified by mass spectrometry (MALDI-TOF/MS). The proteomic results revealed that the presence of DL-3 in MDA-MB-231 cells led to the differential regulation of some proteins that are involved in the cell cycle progression, apoptosis, cytokinesis, modulation of transcription, cellular signaling, and vesicular trafficking. The function of other identified proteins is still unknown. Therefore, our data indicate new directions for the further studies of the pathways engaged in the anticancer action exerted by α-methylene-δ-lactones in cancer cells.

A cytotoxic dimeric furanoheliangolide from Piptocoma rufescens

A new sesquiterpene lactone, rufescenolide C (1), the first furanoheliangolide dimer, was isolated from the leaves of Piptocoma rufescens, collected in the Dominican Republic. Its structure was determined by analysis of its spectroscopic data, with the absolute configuration being established by analysis of the CD spectrum. A plausible biogenesis of this dimer is proposed. This compound showed potent cytotoxicity with an IC50 value of 150 nM, when tested against HT-29 human colon cancer cells.

Anticancer Activity of New Synthetic α-Methylene-δ-Lactones on Two Breast Cancer Cell Lines

Natural products are important leads in drug discovery. The search for effective plant-derived anticancer agents or their synthetic analogues has continued to be of interest to biologists and chemists for a long time. In this report, cytotoxicity and anticancer activity of new synthetic α-methylene-δ-lactones was tested against two breast cancer cell lines, invasive, hormone-independent MDA-MB-231 and hormone-dependent MCF-7. Cytotoxicity was examined using MTT assay. The ability to induce apoptosis and changes in mitochondrial membrane potential was studied by flow cytometry. The expression levels of pro- and anti-apoptotic genes were determined by quantitative real-time PCR. Cancer cell migration and invasion were assessed by wound healing and Matrigel assays. Additionally, secretion of proteins associated with invasiveness, metalloproteinase-9 (MMP-9) and urokinase plasminogen activator (uPA) was investigated using commercial ELISA kits and MMP-9 activity by gelatin zymography. A natural sesquiterpene lactone, parthenolide, was used as a positive control. Screening results showed all four analogues to be highly cytotoxic. The most potent compound of the series, 1-isopropyl-2-methylene-1,2-dihydrobenzochromen-3-one, designated DL-3, which reduced the number of viable MDA-MB-231 and MCF-7 cells with the IC50 values of 5.3 μM and 3.54 μM, respectively, was selected for further research. DL-3 activated the intrinsic pathway of apoptosis, associated with the loss of mitochondrial membrane potential and changes in Bax/Bcl-2 ratio. DL-3 also inhibited the movement of both types of breast cancer cells. Suppression of cell migration and invasion was the result of the decreased secretion of enzymes responsible for the degradation of the extracellular matrix, MMP-9 and uPA. These findings show that the synthetic α-methylene-δ-lactone, DL-3, displays potential to be further explored in the development of new anticancer agents.

A cytotoxic decahydronaphthalenylpropenal derivative and tetrahydrofuran lignans from the stems of Cameraria latifolia

A new decahydronaphthalenylpropenal derivative, (+)-camerarialdehyde (1), a new tetrahydrofuran lignan, (-)-diepiolivil (2), and two known lignans were isolated from a methanol-soluble extract of the stems of Cameraria latifolia, which was obtained from a repository donated to IHVR by Merck Research Laboratories. The structures of compounds 1 and 2 were determined by interpretation of their spectroscopic data, with the absolute configuration of 1 being established by analysis of its CD spectrum. The absolute configuration of the 1,3-diol moiety of 2 was proposed from the CD spectrum induced with dimolybdenum tetraacetate in DMSO solution. All compounds isolated were evaluated against HT-29 human colon cancer cells, and compound 1 was found to show cytotoxicity toward this cell line.

Natural sesquiterpenoids

This review covers the isolation, structural determination, synthesis and chemical and microbiological transformations of natural sesquiterpenoids. The literature from January to December 2012 is reviewed, and 471 references are cited.

Goyazensolide Induces Apoptosis in Cancer Cells in vitro and in vivo

As part of the screening program for anticancer agents from natural sources, the sesquiterpene lactone goyazensolide (GZL) was identified as a potent NF-κB inhibitor. The hollow-fiber assay was used to evaluate the anti-tumor efficacy of GZL in vivo. The mechanistic effects of GZL were evaluated in the HT-29 colonic cell line to reveal the pathway through which GZL exerts its effects. NF-κB subunits p65 and p50 were inhibited, and the upstream mediator IκB kinase (IKKβ) was downregulated in a dose-dependent manner. Apoptosis was mediated by caspase-3, and cell cycle arrest was detected in G1-phase. Consequently, 96% of the cell population was in sub G1-phase after treatment with GZL (10 μM).The antitumor effect of GZL was observed at a dose of 12.5 mg/kg. Cell adhesion was affected as a result of NF-κB inhibition. GZL appears to selectively target the transcription factor NF-κB. In summary, GZL sensitizes HT-29 colon cancer cells to apoptosis and cell death in a dose-dependent manner both in vivo and in vitro, through NF-κB inhibition (IC50 = 3.8 μM). Thus, it is a new potent lead compound for further development into a new effective chemotherapeutic agent.

HPLC-DAD and UV-spectrophotometry for the determination of lychnopholide in nanocapsule dosage form: validation and application to release kinetic study

Simple and sensitive methods using high-performance liquid chromatography-diode array detection (HPLC-DAD) and ultraviolet (UV)-spectrophotometry were developed and compared to quantify lychnopholide (LYC) in poly-ε-caprolactone nanocapsules and to study its release kinetics. Both methods were validated concerning their specificity, linearity, limits of detection and quantification, precision, accuracy and stability. HPLC-DAD analyses were conducted using an RP C18 column, isocratic elution with a methanol-water (60:40 v/v) mobile phase at 0.8 mL/min flow rate and detection at 265 nm. The linear response (r(2) > 0.999) was obtained within a concentration range of 2-25 µg/mL using HPLC-DAD and 5-40 µg/mL using spectrophotometry. Intra-day and inter-day precision were obtained with low relative standard deviation values. The accuracy of the methods was within the range 98-101% for HPLC-DAD and from 96-100% for UV-spectrophotometry. Both methods were suitable to be applied for the determination of drug loading percentage (>96%) and encapsulation efficiency (>90%). Furthermore, the sensitivity of HPLC-DAD method allows studies of LYC release/dissolution in sink conditions. LYC presented 100% dissolution after 24 h, whereas only 60% of LYC was released from the nanocapsule dosage form, with no burst effect. The methods fulfilled all validation parameters evaluated for LYC quantification in the polymeric nanocapsules and have proven to be accurate, selective and sensitive in the previously mentioned applications.