Ent-kaurane glycosides and sesquiterpene lactones of the hirsutinolide type from Vernonia triflosculosa

Chemical constituents from Vernonia bockiana

A new sesquiterpenoid and two pregnane steroids, named vernobockolide C (1) and vernobockones A and B (2 and 3), respevtively, along with a known sesquiterpenoid, 7, 10-epoxy-11-hydroxy-bisabol-2-en-15-al, were isolated from the aerial part of Vernonia bockiana. Their structures were elucidated on the basis of extensive spectroscopic data analysis, especially 2D NMR (HSQC, HMBC, and ROESY). This study further expands the chemical space of this underexplored species.

Vernonia polysphaera Baker: Anti-inflammatory activity in vivo and inhibitory effect in LPS-stimulated RAW 264.7 cells

Species of the Vernonia genius are widely distributed across the world. In traditional communities, they are commonly used in popular medicine for the treatment of inflammatory diseases. The objective of the present study was to evaluate the anti-inflammatory activity of Vernonia polysphaera Baker hydroalcoholic extract. A λ-carrageenan-induced paw edema and peritonitis model was established in BALB/c mice. The in vitro activity of the extract was measured on LPS-stimulated RAW 264.7 cells. There was no toxic effect on mice or on the cells treated with the extract. Animals treated with V. polysphaera extract demonstrated inhibition of paw edema in comparison with the untreated animals at all the analyzed doses. In peritonitis, treatment with the extract at a dose of 500 mg/kg resulted in a lower total leukocyte count in the peritoneal fluid and blood and lower levels of IL-1β, IL-6, TNF-α and PGE-2 than the control group. Cells treated with 50 and 100 μg/mL of the extract exhibited lower levels of nitrite and pro-inflammatory cytokine production and lower COX-2, NF-κB expression. The V. polysphaera extract demonstrated an anti-inflammatory effect, interfering with cell migration, reducing pro-inflammatory cytokine levels and COX-2 expression and consequent interference with PGE-2, as well as inhibiting NF-κB transcription.

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 containing α-methylene-γ-lactones, zaluzanin D 1 and zaluzanin C 2 were isolated from the leaves of Vernonia arborea.

Analysis and fragmentation mechanisms of hirsutinolide-type sesquiterpene lactones by ultra-high-performance liquid chromatography/electrospray ionization linear ion trap Orbitrap mass spectrometry

RATIONALE

Hirsutinolide-type sesquiterpene lactones (SLs) are natural biologically active compounds mainly found in the genus Vernonia. Very few studies have been published about the fragmentation mechanisms of SLs generally and none about hirsutinolides, although they have drawn attention through their biological and taxonomical interest. This work aims to propose a mass spectrometry fragmentation pattern for hirsutinolides in order to detect and to identify them in a botanical extract.

METHODS

The fragmentation pathways of six pure hirsutinolides isolated from Pseudelephantopus spiralis were established by positive ion electrospray high-resolution linear ion trap Orbitrap tandem mass spectrometry (ESI(+)-HRMS(n) ). A resolutive, hyphenated ultra-high-performance liquid chromatography (UHPLC) coupled to diode array detection (DAD) and ESI(+)-HRMS(n) method was then implemented to separate and analyze them. The ionization behaviour and diagnostic product ions were investigated by both methods. The UHPLC/DAD-ESI-HRMS(n) method was applied for the dereplication of a plant extract.

RESULTS

For the six standard compounds, the main fragmentation pattern consists first in the loss of the side chain in the C-8 position followed by the loss of the substituent in the C-13 position. UHPLC/HRMS analyses of hirsutinolides mainly produced sodiated molecules or [M+H-H2 O](+) ions. The high-abundance product ions at m/z 299 and 259 were established to be the characteristic diagnostic ions of the hirsutinolide core. The analysis of a P. spiralis extract further led to the identification of two putative hirsutinolides.

CONCLUSIONS

The UHPLC/DAD-HRMS(n) method combining characteristic fragmentation patterns and the profiles of the product ions generated in the MS and MS/MS spectra is an effective technique for characterizing hirsutinolide-type SLs.

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.

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.

Sesquiterpene lactones from Vernonia scorpioides and their in vitro cytotoxicity

Fresh leaves of Vernonia scorpioides are widely used in Brazil to treat a variety of skin disorders. Previous in vivo studies with extracts of this species had also demonstrated a high antitumor potential. This paper reports isolation of four sesquiterpene lactones (hirsutinolides and glaucolides), together with diacetylpiptocarphol, 8-acetyl-13-etoxypiptocarphol, luteolin, apigenin, and ethyl caffeate from fresh leaves and flowers of Vernonia scorpioides. The hypothesis that hirsutinolide 3 is formed during extraction was verified theoretically using Density Functional Theory. The effects of isolated compounds on in vitro tumor cells were investigated, as well as their genotoxicity by means of an in vitro comet assay. The results indicate that glaucolide 2 and hirsutinolide 4 are toxic to HeLa cells. These compounds were genotoxic in vitro, a property that appears to be related to the presence of their epoxy groups, which has been a more reliable indication of toxicity than substitution on C-13 or the presence of alpha,beta-unsaturated keto-groups. These results need to be replicated in vivo in order to ascertain their toxicity.

Cytotoxic sesquiterpene lactones from Pseudoelephantopus spicatus

Five new sesquiterpene lactones, spicatolides D-H (1-5), along with four known compounds, pitocarphin D (6), 8 alpha-acetoxy-10 alpha-hydroxy-13-O-methylhirsutinolide (7), spicatolide A (8), and 13-O-methylvernojalcanolide 8-O-acetate (9), were isolated from an ethyl acetate extract of the aerial parts of Pseudoelephantopus spicatus. The structures of the new compounds were elucidated on the basis of spectroscopic data interpretation. All of the compounds isolated were evaluated for their cytotoxic effects against five human cancer cell lines. Compounds 1, 3, and 4 showed cytotoxicity (IC50 < 5 micro g/mL) against the Hep3B and MCF-7 cancer cell lines.

Occurrence, biological activities and synthesis of kaurane diterpenes and their glycosides

This paper presents a review on kaurane diterpenes and their glycoside derivatives, covering aspects of their occurrence, biological activities and the synthesis of these natural products and their analogues. First, it shows and classifies diterpenes, in accordance with the already established structural criteria in the literature. Then, kaurane diterpenes are presented, focusing on their chemical structures, occurrence in the plant kingdom and their main, recently described, biological activities. Moreover, the most significant works, published between 1964 and November 2006, which describe the total synthesis or structural transformations of some kaurane diterpenes, including either semisynthetic and/or microbiological methodologies, are consisely reviewed. At this point, some general considerations on glycosides are introduced, and kaurane glycosides are presented and discussed on the basis of their toxic importance and occurrence in the plant kingdom, having focused on related aspects of their biological activities and the relationships between these activities and the structural factors of their molecules. Finally, the principal methods of glycosidation by enzymatic and chemical processes are both presented, and a few papers on the synthesis of kaurane glycosides are succinctly discussed.