Sesquiterpene lactones from Vernonia scorpioides and their in vitro cytotoxicity

The chemistry of Vernonanthura nudiflora (Less.) H. Rob. flowers and its antimicrobial activities

Twenty-one known specialised metabolites were isolated from the flowers of Vernonanthura nudiflora (Less.) H. Rob., the structures of the compounds were established based on 1 D and 2 D NMR spectroscopic experiments. Others 28 compounds were putatively identified using the dereplication technique by UHPLC-HRMS/MS. Twenty-three of the compounds are being reported for the first time in this species. The mixture of sesquiterpene lactones piptocarphins A and B (17 + 18), and the flavone velutin (14) were tested against several microorganisms and showed promising activity against Mycobacterium tuberculosis with MIC of 15.6 μg/mL and 31.2 μg/mL, respectively. Furthermore, 17 + 18 showed greater cytotoxicity against VERO cells (IC₅₀ = 7.0 ± 1.73) compared to compound 14 (IC₅₀ 85.0 ± 10.6 µg/mL). These findings reveal the feasibility of using the UHPLC-ESI-HRMS/MS-based dereplication strategy in complex fractions to identify specialised metabolites, moreover to V. nudiflora flowers being a source of compounds with antimycobacterial potential.

Semisynthetic Sesquiterpene Lactones Generated by the Sensibility of Glaucolide B to Lewis and Brønsted-Lowry Acids and Bases: Cytotoxicity and Anti-Inflammatory Activities

Sesquiterpene lactone (SL) subtypes including hirsutinolide and cadinanolide have a controversial genesis. Metabolites of these classes are either described as natural products or as artifacts produced via the influence of solvents, chromatographic mobile phases, and adsorbents used in phytochemical studies. Based on this divergence, and to better understand the sensibility of these metabolites, different pH conditions were used to prepare semisynthetic SLs and evaluate the anti-inflammatory and antiproliferative activities. Therefore, glaucolide B (1) was treated with various Brønsted-Lowry and Lewis acids and bases-the same approach was applied to some of its derivatives-allowing us to obtain 14 semisynthetic SL derivatives, 10 of which are hereby reported for the first time. Hirsutinolide derivatives 7a (CC₅₀ = 5.0 µM; SI = 2.5) and 7b (CC₅₀ = 11.2 µM; SI = 2.5) and the germacranolide derivative 8a (CC₅₀ = 3.1 µM; SI = 3.0) revealed significant cytotoxic activity and selectivity against human melanoma SK-MEL-28 cells when compared with that against non-tumoral HUVEC cells. Additionally, compounds 7a and 7c.1 showed strongly reduced interleukin-6 (IL-6) and nitrite (NOx) release in pre-treated M1 macrophages J774A.1 when stimulated with lipopolysaccharide. Despite the fact that hirsutinolide and cadinanolide SLs may be produced via plant metabolism, this study shows that acidic and alkaline extraction and solid-phase purification processes can promote their formation.

Metal-Free Temperature-Controlled Regiodivergent Borylative Cyclizations of Enynes: BCl3 -Promoted Skeletal Rearrangement

Metal‐free borylative cyclization of biphenyl‐embedded 1,3,5‐trien‐7‐ynes in the presence of simple and inexpensive BCl₃ provided synthetically useful borylated building blocks. The outcome of the process depends on the reaction temperature, with borylated phenanthrenes obtained at 60 °C and phenanthrene‐fused borylated cyclobutanes formed at 0 °C. Based on DFT calculations, a mechanism for these novel transformations has been proposed, which involves an uncommon skeletal rearrangement, including migration of a methyl group and alkyne fragmentation, unprecedented in BCl₃‐promoted cyclization reactions.

Toxic Potential of Cerrado Plants on Different Organisms

Cerrado has many compounds that have been used as biopesticides, herbicides, medicines, and others due to their highly toxic potential. Thus, this review aims to present information about the toxicity of Cerrado plants. For this purpose, a review was performed using PubMed, Science Direct, and Web Of Science databases. After applying exclusion criteria, 187 articles published in the last 20 years were selected and analyzed. Detailed information about the extract preparation, part of the plant used, dose/concentration tested, model system, and employed assay was provided for different toxic activities described in the literature, namely cytotoxic, genotoxic, mutagenic, antibacterial, antifungal, antiviral, insecticidal, antiparasitic, and molluscicidal activities. In addition, the steps to execute research on plant toxicity and the more common methods employed were discussed. This review synthesized and organized the available research on the toxic effects of Cerrado plants, which could contribute to the future design of new environmentally safe products.

Sesquiterpene lactones from Polydora serratuloides and their quorum sensing inhibitory activity

The leaves of Polydora serratuloides, with the synonym Vernonia perrottetii are widely used as purgative agents for gastrointestinal problems, and other members of Vernonieae have been used in African traditional medicine for decades. A new sesquiterpene lactone of the keto-hirsutinolide type, 13-acetoxy-1(4β),5(6)β-diepoxy-8α-(senecioyloxy)-3-oxo-1,7(11)-germacradiene-12,6-olide 1, was isolated from the hexane extract of its leaves, in addition to the known 13-acetoxy-1,4β-epoxy-8α-(senecioyloxy)-3-oxo-1,5,7(11)-germacratriene-12,6-olide 2. Three common flavonoids (apigenin 3, luteolin 4 and velutin 5) were also isolated. The antibacterial and quorum sensing inhibitory activities of compounds 1 and 2 and crudes extracts showed limited activity on Bacillus subtilis and Staphylococcus aureus, with no activity on Gram negative bacteria. However, quorum sensing (QSI) experiments indicated that 1 and 2, and the four crude extracts had interesting inhibitory activity on the biosensor organism, Chromobacterium violaceum ATCC 12472 in the range of 0.33-5.25 mg mL^-1, with compound 1 being the most effective at 0.33 mg mL^-1.

Anti-inflammatory activity of the sesquiterpene lactone diacethylpiptocarphol in dextransulfate sodium-induced colitis in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Sesquiterpene lactones are organic compounds derived mainly from plants that exhibit anti-inflammatory and antitumor activities being one of the key mechanism of action of NF-kB pathway and synthesis of cytokines such as IL-1 and TNF- α.

AIM OF THE STUDY

The overall objective of the present study was to evaluate the anti-inflammatory action of a sesquiterpene lactone diacethylpiptocarphol (DPC) from Vernonia scorpioides (Lam.) Pers. and parthenolide (PTH) in Balb-c mice with DSS-induced colitis.

MATERIALS AND METHODS

The anti-inflammatory effects of Intraperitonial administration of DPC (5 mg/kg/day) were evaluated in Balb/c mice with DSS-induced colitis, and further the body weight measurement, TNF-α and TGF-β level was determined.

RESULTS

After intraperitoneal treatment for one week, DSS-induced colitis was significantly reduced in mice treated with either of both sesquiterpenes lactones, as witnessed by reduced cellular infiltration, tissue damage, TNF-α production, and enhanced production of TGF-β.

CONCLUSIONS

Sesquiterpene lactone DPC, isolated from Vernonia scorpioides showed anti-inflammatory activity, in this experimental model of colitis the sesquiterpene lactones DPC and PTH exhibit equal anti-inflammatory activity.

ESI-QTof-MS characterization of hirsutinolide and glaucolide sesquiterpene lactones: Fragmentation mechanisms and differentiation based on Na+ /H+ adducts interactions in complex mixture

Sesquiterpene lactones (SL) have been reported with various biological effects. Among the described SL skeletons, hirsutinolide and glaucolide have not been extensively studied by mass spectrometry (MS), especially how to distinguish them in organic matrices. Thus, this paper reports (1) a strategy of their differentiation based on MS behavior during the ionization and (2) a proposal of the fragmentation pattern for both SL-subtypes. ESI(+)-HRMS data of four isolated SL (hirsutinolides 1 and 3; glaucolides 2 and 4) were recorded by direct and UPLC water-sample combined injections. These analyses revealed that hirsutinolides and glaucolides formed [M+Na]⁺ ion during the operation of the direct MS injection, and ([M+Na]⁺ and [M+H-H₂ O]⁺ ) and [M+H]⁺ ions were respectively observed for hirsutinolides and glaucolides during the operation of combined UPLC water and sample MS injection. Computational simulations showed that the complex hirsutinolide (1)-Na⁺ formed with a lower preparation energy compared with the complex glaucolide (2)-Na⁺ . However, despite their different behavior during the ionization process, ESI(+)-HRMS/MS analyses of 1-4 gave similar fragmentation patterns at m/z 277, 259, 241, and 231 that can be used as diagnostic ions for both skeletons. Moreover, the differentiation strategy based on the nature of the complex SL-adducts and their MS/MS fragmentation pattern were successfully applied for the chemical characterization of the extract from Vernonanthura tweedieana using UPLC-ESI-HRMS/MS. Among the characterized metabolites, SL with hirsutinolide and glaucolide skeletons showed the aforementioned diagnostic fragments and an ionization behavior that was similar to those observed during the water-sample combined injection.

Bioactive Sesquiterpene Lactones Isolated from the Whole Plants of Vernonia cinerea

Twelve sesquiterpene lactones were isolated from the whole plants of Vernonia cinerea. These included eight new compounds, vercinolides A-H (1-8), along with four known substances (9-12). The structures of the new compounds were determined by 1D and 2D NMR experiments and mass spectrometric methods. The absolute configurations of compounds 1-8 were determined by Mosher experiments and ECD data. Compounds 1-8 are the first examples of a new class of sesquiterpene lactones possessing a rare 4α,10α-ether ring and a 2,14-ether ring. Compounds 1-4, 6, 8, 10, and 12 were evaluated for their cytotoxic and anti-inflammatory activities. Compounds 10 and 12 exhibited inhibitory effects against nitric oxide production in lipopolysaccharide-activated RAW 264.7 mouse macrophage cells with IC₅₀ values of 21 and 23 μM, respectively. Both compounds were inactive for HeLa cells (IC₅₀ > 10 μM).

Antiproliferative, cytotoxic and apoptotic activity of the bentonite transformation of sesquiterpene lactone glaucolide B to 5β-hydroxy-hirsutinolide on tumor cell lines

Numerous chemical compounds isolated from medicinal plants have anti-tumor properties, the effects of which on human cancer cells are currently under study. Here, the chemical transformation of glaucolide B were performed to produce a hirsutinolide. The antiproliferative and cytotoxic activity of 5β-hydroxy-hirsutinolide and its ability to induce apoptosis in tumor and non-tumor cells (lymphocyte cultures and the normal HaCaT cell line) (1a) are reported. We ascertained that compound 1a exerts an inhibitory effect on the proliferation of SK-Lu-1, MDA-MB-231 and CaSki cells in a dose-dependent manner at IC₅₀ values of 15, 18 and 30 μg/ml, respectively. The proliferation of lymphocyte cells treated with 1a was inhibited at a range from 14 to 28%, but the HaCaT cell line was not affected, suggesting that compound 1a has a selective action. Cytotoxic activity was evaluated by detecting the lactate dehydrogenase enzyme in supernatants from tumor and non-tumor cells. The 1a compound exhibited low or null cytotoxic activity in both cell types. The presence of apoptotic bodies and active caspase-3 in tumor cell lines treated with compound 1a are suggestive of apoptotic cell death. Notably, flow cytometry evaluation did not detect the presence of active caspase-3 on lymphocytes treated with this compound. Our results suggest that 5β-hydroxy-hirsutinolide is a molecule with antiproliferative activity and low cytotoxic activity in tumor and non-tumor cells; this induces apoptotic cell death in tumor cell lines through selective action. Hence, this lactone could be considered a molecule worthy of study as an anti-tumor agent with therapeutic potential.

Isolation of a New Sesquiterpene Lactone From Vernonia Zeylanica (L) Less and its Anti-Proliferative Effects in Breast Cancer Cell Lines

Background/Objective:

Vernonia zeylanica (L) less is an endemic plant to Sri Lanka. The present study was designed to isolate potential cytotoxic compound/s from chloroform and ethyl acetate extracts of V. zeylanica by bio-activity guided isolation and to evaluate its anti-proliferative effects in three breast cancer phenotypes (MCF -7, MDA-MB-231, SKBR-3).

Methods:

Combined chloroform and ethyl acetate extracts were subjected to chromatographic separations to isolate a compound (1) and the structure of the isolated compound was elucidated using 1H, 13C and mass spectroscopic techniques. Cytotoxic effects of the compound were evaluated by the sulforhodamine B (SRB) and the MTT (3- (4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays. Effects of the compound on apoptosis were evaluated by fluorescent microscopy, caspase 3/7 activation, DNA fragmentation and real time PCR. Effects of the compound on the expression of heat shock protein complex were also evaluated by real time PCR and immunofluorescence.

Results:

Isolated compound was identified as a new sesquiterpene lactone (vernolactone). The compound mediated significant cytotoxic effects in SKBR-3 and MDA-MB-231 breast cancer cells, with little effect in MCF-7 and normal mammary epithelial MCF-10A cells. Morphological changes, DNA fragmentation, increased caspase 3/7 activities and up-regulation of p53, Bax and down regulation of Survivin confirmed the proapoptotic effects of the compound. Significant inhibition of HSP complex related genes were also observed in SKBR-3 and MDA-MB-231 breast cancer cells.

Conclusion:

Overall results indicate that vernolactone can mediate its cytotoxic effects via apoptosis and modulating the HSP complex.

Synthesis and anticancer studies of Michael adducts and Heck arylation products of sesquiterpene lactones, zaluzanin D and zaluzanin C from Vernonia arborea

Sesquiterpene lactones containing α-methylene-γ-lactones, zaluzanin D 1 and zaluzanin C 2 were isolated from the leaves of Vernonia arborea. Several diverse Michael adducts (3-22) and Heck arylation analogs (23-34) of 1 have been synthesized by reacting with various amines and aryl iodides, respectively and were assayed for their in vitro anticancer activities against human breast cancer cell lines MCF7 and MDA-MB-231. Among all the synthesized analogs, Michael adducts 9 and 10 showed better anticancer activities as compared to 1. However, among these compounds, only 10 has minimal cytotoxic effect on normal breast epithelial MCF10A cells. Our detailed mechanistic studies reveal that compounds 9 and 10 execute their antiproliferative activity through induction of apoptosis and thereby inhibit the cancer cells proliferation and compound 10 could be a lead compound for designing potential anti-cancer compound.

Sesquiterpene Lactones from Vernonia cinerascens Sch. Bip. and Their in Vitro Antitrypanosomal Activity

In the endeavor to obtain new antitrypanosomal agents, particularly sesquiterpene lactones, from Kenyan plants of the family Asteraceae, Vernonia cinerascens Sch. Bip. was investigated. Bioactivity-guided fractionation and isolation in conjunction with LC/MS-based dereplication has led to the identification of vernodalol (1) and isolation of vernodalin (2), 11β,13-dihydrovernodalin (3), 11β,13-dihydrovernolide (4), vernolide (5), 11β,13-dihydrohydroxyvernolide (6), hydroxyvernolide (7), and a new germacrolide type sesquiterpene lactone vernocinerascolide (8) from the dichloromethane extract of V. cinerascens leaves. Compounds 3–8 were characterized by extensive analysis of their 1D and 2D NMR spectroscopic and HR/MS spectrometric data. All the compounds were evaluated for their in vitro biological activity against bloodstream forms of Trypanosoma brucei rhodesiense and for cytotoxicity against the mammalian cell line L6. Vernodalin (2) was the most active compound with an IC₅₀ value of 0.16 µM and a selectivity index of 35. Its closely related congener 11β,13-dihydrovernodalin (3) registered an IC₅₀ value of 1.1 µM and a selectivity index of 4.2.

Sesquiterpene lactone! a promising antioxidant, anticancer and moderate antinociceptive agent from Artemisia macrocephala jacquem

Background

Sesquiterpene lactones (STLs) make a diverse and huge group of bio-active constituents that have been isolated from several plant families. However, the greatest numbers are present in Asteraceae family having more than 3000 different reported structures. Recently several researchers have reported that STLs have significant antioxidant and anticancer potentials.

Methods

To investigate the antioxidant, anticancer and antinociceptive potentials of STLs, gravity column chromatography technique was used for isolation from the biologically rich chloroform fraction of Artemisia macrocephala Jacquem. The antioxidant activity of the isolated STLs was determined by DPPH and ABTS free radical scavenging activity, anticancer activity was determined on 3 T3, HeLa and MCF-7 cells by MTT assay while the antinociceptive activity was determined through acetic acid induced writhings, tail immersion method and formalin induced nociception method.

Results

The results showed that the STLs of Artemisia macrocephala possesses promising antioxidant activity and also it decreased the viability of 3 T3, HeLa and MCF-7 cells and mild to moderate antinociceptive activity.

Conclusion

Sesquiterpenes lactones (STLs) are widely present in numerous genera of the family Asteraceae (compositae). They are described as the active constituents used in traditional medicine for the treatment of various diseases. The present study reveals the significant potentials of STL and may be used as an alternative for the management of cancer. Anyhow, the isolated compound is having no prominent antinociceptive potentials.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1517-y) contains supplementary material, which is available to authorized users.

A new lanostane-type triterpene and sesquiterpene lactones from Vernonia leopoldii and their in vitro cytotoxicity

Investigation of the aerial parts of Vernonia leopoldii (Sch. Bip.) Vatke afforded a new lanostane-type triterpene along with known hirsutinolide-type sesquiterpene lactones and flavonoid glycosides, all are identified for the first time in this species. The new compound was identified as lanost-3β, 23S-dihydroxy-22(31)-ene. The structures of the isolated compounds were elucidated based on spectroscopic evidence. The hirsutinolides and the triterpene were evaluated for their cytotoxicity against four human cancer cell lines using MTT assay.

Evaluation of antiplasmodial and antileishmanial activities of herbal medicine Pseudelephantopus spiralis (Less.) Cronquist and isolated hirsutinolide-type sesquiterpenoids

ETHNOPHARMACOLOGICAL RELEVANCE

Pseudelephantopus spiralis (Less.) Cronquist is distributed in the Caribbean, Mesoamerica and Latin America. Preparations of the plant are traditionally used in Latin America for the treatment of various diseases including fever, malaria, and spleen or liver inflammations.

MATERIALS AND METHODS

Aerial parts of P. spiralis were extracted with either ethanol or distilled water. Seven hirsutinolide-type sesquiterpenoids were isolated: 8-acetyl-13-ethoxypiptocarphol (1), diacetylpiptocarphol (2), piptocarphins A (3), F (4) and D (5), (1S(*),4R(*),8S(*),10R(*))-1,4-epoxy-13-ethoxy-1,8,10-trihydroxygermacra-5E,7(11)-dien-6,12-olide (6), and piptocarphol (7). Extracts and isolated compounds (2, 3, 5-7) were screened for their in vitro antiplasmodial activity against the chloroquine-resistant Plasmodium falciparum strain FcM29-Cameroon and antileishmanial activity against three stages of Leishmania infantum. Their cytotoxicities were also evaluated against healthy VERO cell lines and J774A.1 macrophages, the host cells of the Leishmania parasites in humans.

RESULTS

Aqueous extracts showed a greater inhibitory effect than alcoholic extracts, with IC50 on P. falciparum of 3.0µg/mL versus 21.1µg/mL, and on L. infantum of 13.4µg/mL versus >50µg/mL. Both extracts were found to be cytotoxic to VERO cells (CC50<3µg/mL). Sesquiterpene lactones 2 and 3 showed the best activity against both parasites but failed in selectivity. Carbon 8 hydroxylated hirsutinolides 5-7 presented the particularity of exhibiting two conformers observed in solution during extensive NMR analyses in CD3OD and UHPLC-MS. The presence of a hydroxyl function at C-8 decreased the activity of 5-7 on the two parasites and also on VERO cells.

CONCLUSION

The antiplasmodial activity displayed by the aqueous extract explains the traditional use of P. spiralis in the treatment of malaria. This activity seems to be attributable to the presence of sesquiterpene lactones 2 and 3, the most active against P. falciparum. Aqueous extract and compounds 2, 3 and 6 were also active against L. infantum but lacked in selectivity due to their cytotoxicity towards macrophages. Exploring the safety and antiplasmodial efficacy of this traditional remedy will require further toxicological and in vivo studies in the light of the cytotoxicity towards healthy cell lines displayed by the aqueous extract and compounds 2 and 3.

Sesquiterpene lactones from the aerial parts of Vernonia blumeoides growing in Nigeria

Four eudesmanolide sesquiterpene lactones (1-4) were isolated from the aerial parts of Vernonia blumeoides used in Nigerian ethnomedicine for the treatment of diarrhea and malaria. Compound 1 demonstrated limited but interesting antibacterial activity against Bacillus, Staphylococcus and Streptococcus species. The crystal structure of 1 allowed the absolute configuration of the stereocentres in the molecule to be assigned.

Lactones with methylcyclohexane systems obtained by chemical and microbiological methods and their antimicrobial activity

Eight new lactones (δ-chloro-, δ-bromo- and δ-iodo-γ-lactones), each with a methylcyclohexane ring, were obtained by chemical means from (4-methylcyclohex-2-en-1-yl) acetic acid or (6-methylcyclohex-2-en-1-yl) acetic acid. Whole cells of ten fungal strains (Fusarium species, Syncephalastrum racemosum and Botrytis cinerea) were tested on their ability to convert these lactones into other products. Some of the tested fungal strains transformed chloro-, bromo- and iodolactone with a methyl group at C-5 into 2-hydroxy-5-methyl-9-oxabicyclo[4.3.0]nonan-8-one during hydrolytic dehalogenation. When the same lactones had the methyl group at C-3, no structural modifications of halolactones were observed. In most cases, the optical purity of the product was low or medium, with the highest rate for chlorolactone (45.4%) and iodolactone (45.2% and 47.6%). All of the obtained compounds were tested with reference to their smell. Seven halolactones and the hydroxylactone obtained via biotransformation of halolactones with 5-methylcyclohexane ring were examined for their antimicrobial activity. These compounds were capable of inhibiting growth of some bacteria, yeasts and fungi.

A metabolomic protocol for plant systematics by matrix-assisted laser-desorption/ionization time-of flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of flight mass spectrometry (MALDI-TOF MS) has been widely used for the identification and classification of microorganisms based on their proteomic fingerprints. However, the use of MALDI-TOF MS in plant research has been very limited. In the present study, a first protocol is proposed for metabolic fingerprinting by MALDI-TOF MS using three different MALDI matrices with subsequent multivariate data analysis by in-house algorithms implemented in the R environment for the taxonomic classification of plants from different genera, families and orders. By merging the data acquired with different matrices, different ionization modes and using careful algorithms and parameter selection, we demonstrate that a close taxonomic classification can be achieved based on plant metabolic fingerprints, with 92% similarity to the taxonomic classifications found in literature. The present work therefore highlights the great potential of applying MALDI-TOF MS for the taxonomic classification of plants and, furthermore, provides a preliminary foundation for future research.

The Anti-cancer Activity of Vernonia divaricata Sw against Leukaemia, Breast and Prostate Cancers In Vitro

BACKGROUND

Vernonia divaricata is one of five endemic Vernonia species of Jamaica. The ethno-medicinal uses of other species have been established, however, scientific validation of this species has not yet been done and as such this paper is aimed at identifying the anti-cancer activity of V divaricata against leukaemia, breast and prostate cancer cell lines.

METHODS

Leaves and stems of V divaricata were dried and milled into powder. The crude hexane and methanol extracts of the leaves and stems were obtained and bio-assayed using WST-1 cell proliferation assay against leukaemia, breast and prostate cancer cell lines.

RESULTS

The crude hexane and methanol extracts of V divaricata were able to significantly retard the growth of the MCF-7 (breast), HL-60 (leukaemia) and the PC-3 (prostate) cancer cell lines. The crude methanol extract of the stem was the strongest, exhibiting anti-proliferation activity with IC50 values of 10.14, 12.63 and 9.894 µg/ml for the HL-60, MCF-7 and PC-3 cancer cell lines, respectively, with the most potent toward prostate cancer.

CONCLUSION

The medicinal use of V divaricata as an anti-cancer agent was corroborated as the crude hexane and methanol extracts demonstrated potent anti-proliferation activity and as such hold potential for further research and development into a drug to prevent or treat various cancers.

Metabolomics as a potential chemotaxonomical tool: application in the genus Vernonia schreb

The taxonomic classification of the genus Vernonia Schreb is complex and, as yet, unclear. We here report the use of untargeted metabolomics approaches, followed by multivariate analyses methods and a phytochemical characterization of ten Vernonia species. Metabolic fingerprints were obtained by accurate mass measurements and used to determine the phytochemical similarities and differences between species through multivariate analyses approaches. Principal component analysis based on the relative levels of 528 metabolites, indicated that the ten species could be clustered into four groups. Thereby, V. polyanthes was the only species with presence of flavones chrysoeriol-7-O-glycuronyl, acacetin-7-O-glycuronyl and sesquiterpenes lactones piptocarphin A and piptocarphin B, while glaucolide A was detected in both V. brasiliana and V. polyanthes, separating these species from the two other species of the Vernonanthura group. Species from the Lessingianthus group were unique in showing a positive response in the foam test, suggesting the presence of saponins, which could be confirmed by metabolite annotation. V. rufogrisea showed a great variety of sesquiterpene lactones, placing this species into a separate group. Species within the Chrysolaena group were unique in accumulating clovamide. Our results of LC-MS-based profiling combined with multivariate analyses suggest that metabolomics approaches, such as untargeted LC-MS, may be potentially used as a large-scale chemotaxonomical tool, in addition to classical morphological and cytotaxonomical approaches, in order to facilitate taxonomical classifications.

Sesquiterpene lactones: adverse health effects and toxicity mechanisms

Sesquiterpene lactones (STLs) present a wide range of biological activities, mostly based on their alkylating capabilities, which underlie their therapeutic potential. These compounds are the active constituents of a variety of plants, frequently used as herbal remedies. STLs such as artemisinin and its derivatives are in use as first-line antimalarials while others, such as parthenolide, have recently reached cancer clinical trials. However, the toxicological profile of these compounds must be thoroughly characterized, since the same properties that make STL useful medicines can also cause severe toxicity. STL-containing plants have long been known to induce a contact dermatitis in exposed farm workers, and also to cause several toxic syndromes in farm animals. More recently, concerns are been raised regarding the genotoxic potential of these compounds and the embryotoxicity of artemisinins. A growing number of STLs are being reported to be mutagenic in different in vitro and in vivo assays. As yet no systematic studies have been published, but the genotoxicity of STLs seems to depend not so much on direct DNA alkylation as on oxidative DNA damage and other partially elucidated mechanisms. As the medicinal use of these compounds increases, further studies of their toxic potential are needed, especially those focusing on the structural determinants of genotoxicity and embryotoxicity.

Polyacetylenes from the leaves of Vernonia scorpioides (Asteraceae) and their antiproliferative and antiherpetic activities

Polyacetylenes constitute an underexplored and unstable class of compounds that are found mainly in the Apiaceae, Araliaceae and Asteraceae families. Vernonia scorpioides (Lam.) Pers., Asteraceae is a lianous neotropical herb that usually grows in soils that have been deforested and are of poor quality. It is used in folk medicine for the treatment of several skin conditions. This study addresses the characterisation of eight polyacetylenes isolated from the leaves of V. scorpioides. Their structures were established on the basis of 1D and 2D NMR spectroscopy and MS analysis. Ab initio calculations including solvent effects were employed to aid the elucidation of the absolute configurations of the compounds. The in vitro antiproliferative and anti-herpetic activities of the polyacetylenes were determined. The isolated compounds presented no inhibitory effect against a human cell line of non-small cell lung cancer, but presented a mild non-selective in vitro antiviral activity, although their corresponding glycosides were inactive.

Cytotoxic, antitumour and antimetastatic activity of two new polyacetylenes isolated from Vernonia scorpioides (Lam.) Pers

Vernonia scorpioides (Lam.) Pers., popularly known as Enxuga, Erva-de-São Simão and Piracá, has been used in folk medicine for its anti-inflammatory, wound healing and antimicrobial properties. Two polyacetylenes, 5-octa-2,4,6-triynyl-furan-2(5H)-one (1) and 8'-hydroxy 3-4 dihydrovernoniyne (2), were isolated from the dichloromethane extract fraction of V. scorpioides. In this study, polyacetylene 1 demonstrated a more potent cytotoxic activity than 2 in the tumour cell lines examined, and cytotoxicity was found to be comparable to a commercial drug (p > 0.05) in melanoma cells. No significant cytotoxic effect was observed in normal cell lines. Furthermore, polyacetylene 1 induced an in vitro increase in caspase-3 activity in B16F10 cells. When polyacetylene 1 was administered intraperitoneally (i.p.) in mice, a reduction in solid tumour volume and metastasis was observed in mice injected with B16F10 cells. An increase in locomotor activity was also observed in mice with solid tumours, and an inhibition of mechanical hypersensitivity was observed in a mouse model of metastasis. Notably, no significant morphological change was observed in several organs harvested from the treated mice. In conclusion, in vitro and in vivo anticancer activity of polyacetylene 1 was consistently observed and involved the induction of apoptosis by the activation of caspase-3. The anticancer activity demonstrated by polyacetylene 1, together with the absence of preliminary toxicological effects, represents a new and interesting option for the management of neoplastic disease.

Antiplasmodial activity of sesquiterpene lactones and a sucrose ester from Vernonia guineensis Benth. (Asteraceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Aqueous preparations of Vernonia guineensis Benth. (Asteraceae) are used in Cameroonian folk medicine as a general stimulant and to treat various illnesses and conditions including malaria, bacterial infections and helminthic infestations.

MATERIALS AND METHODS

Ten gram samples of the leaf and tuber powders of Vernonia guineensis were extracted separately using dichloromethane, methanol and distilled water. The extracts were dried in vacuo and used in bioassays. These extracts and three compounds previously isolated from Vernonia guineensis [vernopicrin (1), vernomelitensin (2) and pentaisovalerylsucrose (3)] were screened for antiplasmodial activity against chloroquine (CQ)-sensitive (Hb3) and CQ-resistant (Dd2) Plasmodium falciparum lines.

RESULTS

Crude extracts and pure compounds from Vernonia guineensis showed antiplasmodial activity against both Hb3 and Dd2. The IC50 values of extracts ranged from 1.64 to 27.2 µg/ml for Hb3 and 1.82-30.0 µg/ml for Dd2; those for compounds 1, 2 and 3 ranged from 0.47 to 1.62 µg/ml (1364-1774 nM) for Hb3 and 0.57-1.50 µg/ml (1644-2332nM) for Dd2. None of the crude extracts or pure compounds was observed to exert toxic effects on the erythrocytes used to cultivate the Plasmodium falciparum lines.

CONCLUSION

In Cameroonian folk medicine, Vernonia guineensis may be used to treat malaria in part due to the antiplasmodial activity of sesquiterpene lactones (1, 2), a sucrose ester (3) and perhaps other compounds present in crude plant extracts. Exploring the safety and antiplasmodial efficacy of these compounds in vivo requires further study.

A review of the medicinal potentials of plants of the genus Vernonia (Asteraceae)

ETHNOPHARMACOLOGICAL RELEVANCE

The Vernonia genus has about one thousand species and members of the genus are widely used as food and medicine. The aim of this review is to analyze published data on the ethnomedicinal, ethnoveterinary and zoopharmacognostic uses of plants of the Vernonia genus. This will help to identify the state of ethnopharmacological knowledge in regard to this genus and to propose future research priorities.

MATERIALS AND METHODS

The major scientific databases including SciFinder, Sciencedirect, Medline and Google Scholar were queried for information on Vernonia genus using various keyword combinations. The International Plant Name Index was also used to verify the names of species and authors.

RESULTS

A total of 109 Vernonia species were reported in the literature to have medicinal properties. One hundred and five (105) plants were linked to the treatment or management of 44 human diseases or health conditions. Plants of the genus also feature in ethnoveterinary and zoopharmacognostic practices. A total of 12 vernonia species were identified to be used in ethnoveterinary medicine while 2 species are used in self medication practices by chimpanzees and gorillas. In vitro and in vivo research studies reporting the validation of the medicinal properties of some species were also reviewed. One hundred and three bioactive compounds isolated from various Vernonia species were also identified. Vernonia amygdalina was identified as the most frequently used member of the Vernonia genus. The Vernolides, a class of sesquiterpene lactone were identified as the most studied compounds from the genus and show interesting bioactivity in antiplasmodial, antileishmanial, antischistosomial, cytotoxicity, antimicrobial and anti-inflammatory assays.

CONCLUSION

On the basis of results from a combination of in vitro and in vivo efficacy and toxicity studies reported, Vernonia amygdalina holds the most promise for development into a nutraceutical against diabetes and malaria while Vernonia cinerea has potential against cancer and inflammatory conditions. Vernolide A is so far the most promising single agent from a Vernonia species that has potential for development into an anticancer agent. The other Vernonia species and isolated compounds require further studies to ascertain their medicinal potentials.

Cytotoxic sesquiterpene lactones from the leaves of Vernonia guineensis Benth. (Asteraceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Vernonia guineensis Benth. (Asteraceae) preparations are used in folk medicine in Cameroon to treat a number of ailments, including prostate cancer and malaria, and is used as an anthelmintic, adaptogen and antidote. The aim of this study was to continue the validation of the activity of Vernonia guineensis Benth. extracts and isolated molecules against cancer cell lines following the previous isolation of an anti-prostate cancer sugar ester from the root extract.

MATERIALS AND METHODS

Acetone extracts of Vernonia guineensis Benth. leaves were tested for activity against 10 cancer cell lines (Breast-MDA-MB-231, Breast-MCF-7, Colon-HCT-116, Leukemia-HL-60, Lung-A549, Melanoma-A375, Ovarian-OVCAR3, Pancreas-Mia-paca, Prostate-PC-3 and Prostate-DU-145). The acetone extract was subjected to bioactivity guided fractionation. Anti-proliferation and clonogenic activity of the isolated compounds were tested. The WST-1 assay was used for the anti-proliferation activity, while the standard clonogenic test was used to determine the clonogenic activity.

RESULTS

The acetone extract of Vernonia guineensis Benth. demonstrated in vitro activity ranging from IC50 4-26μg/mL against the 10 cell lines. Activity guided fractionation of this extract yielded two sesquiterpene lactones, isolated for the first time from the genus Vernonia. The compounds were characterized using spectroscopic experiments, including a combination of 1D and 2D NMR data. Vernopicrin (1) and Vernomelitensin (2) demonstrated in vitro activity against human cancer cell lines with IC50 ranging from 0.35-2.04μM (P<0.05) and 0.13-1.5μM (P<0.05), respectively, between the most and least sensitive cell lines for each compound. Vernopicrin was most active against the human melanoma (A375) cell line and least active against the lung cancer (A549) cell line, while Vernomelitensin was also most active against the human melanoma (A375) cell line and least active against the breast cancer (MCF-7) cell line. Both compounds also demonstrated anticlonogenic activity.

CONCLUSION

The cytotoxicity demonstrated by the crude extract and isolated sesquiterpenes against cancer cell lines highlights the medicinal potential of V. guineensis. The selective anti-proliferation and dose dependent anticlonogenic activities suggest that the identified sesquiterpenes could be potential antitumor agents.

Sesquiterpene lactones as drugs with multiple targets in cancer treatment: focus on parthenolide

Sesquiterpene lactones (SLs) constitute a large and diverse group of biologically active plant compounds that possess anti-inflammatory and antitumor activity. The subclass germacranolides is one of the major groups of SLs. It includes parthenolide, a highly cytotoxic SL that is being tested in clinical trials as an anti-cancer agent. In this review, we focus on SL antitumor activity related to cell-cycle arrest, differentiation, apoptosis induction through the intrinsic pathway, and sensitization of the extrinsic pathway. We also address the regression of tumors in response to cotreatment with conventional chemotherapeutics. We review the nuclear factor-κB-targeted anti-inflammatory activity in vitro and in vivo and relate it to the SL structural features involved in the molecular mechanisms. It is obvious that SLs are emerging as promising anticancer agents, but more investigations are required to fully understand the molecular mechanisms of known SLs in different cell death modalities and how these mechanisms contribute toward the potent antitumor and anti-inflammatory activities of SLs.

Effectiveness of Vernonia scorpioides ethanolic extract against skin inflammatory processes

ETHNOPHARMACOLOGICAL RELEVANCE

Vernonia scorpioides (Asteraceae) is a native Brazilian medicinal plant that is commonly used to treat skin disorders. Considering the traditional use of Vernonia scorpioides and the lack of information about its pharmacological properties, we investigated the topical anti-inflammatory effect of the ethanolic extract of Vernonia scorpioides (EEVS) on acute and chronic cutaneous inflammation models in mouse.

MATERIALS AND METHODS

The topical anti-inflammatory effect of EEVS was evaluated against acute models (12-O-tetradecanoylphorbol acetate (TPA)- and arachidonic acid (AA)-induced mouse ear oedema) and chronic models (multiple applications of croton oil).

RESULTS

The EEVS caused a dose-related inhibition of oedema in both the TPA- and AA-induced acute models (DI(50)=0.24 and 0.68 mg/ear with an inhibition of 80 ± 5% and 65 ± 5%, respectively, for 1mg/ear). In addition, the TPA-induced increase in myeloperoxidase activity (MPO) in the ear was reduced (77 ± 8%) by the topical application of EEVS. In the chronic model, the EEVS reduced all parameters evaluated: oedema formation (31 ± 2%), epidermal hyperproliferation (histology) and MPO (25 ± 10%). However, the topical treatment of EEVS had no effect on N-acetyl-β-d-glucosaminidase activity. The EEVS effectively interfered in the ear oedema on the delayed-type hypersensitivity reaction induced by oxazolone. The topical treatment with EEVS performed on both phases or only on the elicitation phase caused the inhibition of the ear oedema-induced by oxazolone in 42.9% and 63.4%, respectively, when compared to control animals (sensitized and challenged).

CONCLUSIONS

The results suggest that EEVS is effective as a topical anti-inflammatory agent in acute and chronic inflammatory processes and that its action is markedly influenced by the inhibition of neutrophil migration into inflamed tissue as well as by epidermal hyperproliferation.

Antileishmanial sesquiterpene lactones from Pseudelephantopus spicatus, a traditional remedy from the Chayahuita Amerindians (Peru). Part III

ETHNOPHARMACOLOGICAL RELEVANCE

The study of traditional remedies used by the Chayahuita, an ethnic group from the Peruvian Amazonia, has prompted us to investigate in detail the ethanolic extract of Pseudelephantopus spicatus (Juss. ex Aubl.) C.F. Baker, which has demonstrated strong biological activity towards Leishmania amazonensis. Our goal was to discover the active compound of this plant-based remedy.

MATERIALS AND METHODS

A bioguided fractionation of the crude extract was undertaken based on the biological activity recorded against Leishmania amazonensis axenic amastigotes in in vitro bioassays.

RESULTS

Three strongly to moderately active compounds were isolated: two hirsutinolides (the 8,13-diacetyl-piptocarphol and the 8-acetyl-13-O-ethyl-piptocarphol) and ursolic acid. IC(50) against Leishmania amazonensis axenic amastigotes are respectively 0.2, 0.37 and 0.99 μM (while IC(50) of amphotericin B is 0.41 μM). These compounds have never been isolated from this plant species, and germacranolides have never been identified as potential antileishmanial agents.

CONCLUSIONS

The compounds isolated from Pseudelephantopus spicatus account for the antileishmanial activity of the plant, thus giving support to its use by the Chayahuita in Peru.