New Sesquiterpene Lactones from the Aerial Parts of Pseudoelephantopus spicatus

Brønsted Acid-Promoted Cyclodimerization of α,β-Unsaturated γ-Ketoesters: Construction of Fused Pyrano-ketal-lactones and γ-Ylidene-butenolides

Unprecedented MsOH-promoted diastereoselective cascade dimerization and intramolecular lactonization of readily accessible α,β-unsaturated γ-ketoesters are presented. The results obtained in this work, control experiments, and density functional theory (DFT) calculations suggested that the initial enolization and E to Z isomerization/equilibration of olefin (C=C) of substrate α,β-unsaturated γ-ketoesters give a Z-isomer preferentially over an E-isomer. Subsequently, the Z-isomer undergoes intermolecular annulation with α,β-unsaturated γ-ketoesters via domino Michael addition/ketalization/lactonization steps to furnish fused tetracyclic pyrano-ketal-lactone. However, the Z-isomer prefers intramolecular trans-esterification in a competing pathway and gives bicyclic γ-ylidene-butenolide. The key features of this work include simple Brønsted acid catalysis, the formation of three bonds, two rings, and three contiguous stereogenic centers in a single step, DFT calculations, and the assignment of relative stereochemistry through X-ray diffraction (XRD) and two-dimensional (2D) nuclear magnetic resonance (NMR) analyses.

Hirsutinolide- and Cadinanolide-type Sesquiterpene Lactones from Lessingianthus rubricaulis (Vernonieae, Asteraceae)

Sesquiterpene lactones are an important class of secondary metabolites frequently isolated from Lessingianthus genus that present a variety of biological properties, such as antimalarial, anti-inflammatory, antileishmanial, antitrypanosomal and anticancer. The limited phytochemical studies and the importance of this class of compounds isolated from Lessingianthus led us to study this genus. In this work, we focused on the phytochemical investigation and dereplication based on UHPLC-HRMS/MS and molecular networking of L. rubricaulis. Chemical investigation resulted in the isolation of several hirsutinolide-type sesquiterpene lactones including a new hirsutinolide derivative, 8,10α-hydroxy-1,13-bis-O-methylhirsutinolide, besides a cadinanolide and flavonoids. The dereplication study resulted in the identification of three known flavonoids, six known hirsutinolides and two known cadinanolides. Moreover, a fragmentation pathway for cadinanolide-type sesquiterpene lactones was proposed. These results contribute to chemotaxonomic studies and demonstrates the potential of Lessingianthus genus.

Highly Modified Sesquiterpene Lactones with Cytotoxic Activities from Strobocalyx chunii

Three new germacranolide sesquiterpene lactones (SLs), strochunolides A-C (1-3, respectively), and a new guaianolide SL, strochunolide D (4), were isolated from Strobocalyx chunii and structurally characterized. Compound 1 is the first example of a dihomo-germacranolide SL, characterized by an unprecedented 6/10/5 tricyclic scaffold incorporating an additional fused δ-lactone C-ring. The structure of a known germacranolide SL, spicatolide C (5), was revised as its 8-epimer. Compound 3 exhibited potent in vitro cytotoxic activity against the HL-60 cell line, with an IC50 value of 0.18 ± 0.01 μM.

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.

Hepatoprotective effects of reynosin against thioacetamide-induced apoptosis in primary hepatocytes and mouse liver

The aim of this study was to identify the hepatoprotective effects of reynosin, sesquiterpenes from the leaves of Laurus nobilis, against thioacetamide (TAA)-induced apoptosis in primary hepatocyte cultures and an in vivo mouse model. Rat hepatocytes were isolated and pretreated with 0.13, 0.64, or 3.22 μM reynosin and then exposed to 100 mM TAA. Reynosin treatment significantly inhibited TAA-induced apoptosis and hepatocellular DNA damage in primary rat hepatocytes. We observed an increase in levels of antiapoptotic Bcl-2, Bcl-XL mRNA and a decrease in levels of proapoptotic Bax mRNA following reynosin treatment of hepatocytes. Apoptosis in BALB/c mice was induced with intra-peritoneal injection of 200 mg/kg TAA for 2 weeks every other day. Then reynosin (5 mg/kg) and TAA were intragastrically given for 3 weeks every other day. Aspartate aminotransferase and alanine aminotransferase levels in the blood of mice were decreased in the reynosin administration group. Bcl-2 and Bcl-XL mRNA levels were increased, and the Bax mRNA level was decreased in reynosin-treated mice. Thus, reynosin inhibited TAA-induced apoptosis in primary hepatocytes and an in vivo mouse model.

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.

Ta'ta', Huayani: perception of leishmaniasis and evaluation of medicinal plants used by the Chayahuita in Peru. Part II

AIM OF THE STUDY

A knowledge attitude and practice study centred on leishmaniasis and its treatment was performed among the Chayahuita, an Amazonian Peruvian ethnic group living in an endemic area. This study documents traditional Chayahuita plant's use and disease concepts. Also, activity of some medicinal plants used by the Chayahuita is highlighted and discussed.

MATERIALS AND METHODS

Ninety-three Chayahuita people were interviewed, following a semi-structured questionnaire focussed on disease knowledge and perception, personal attitude and healing practices. Simultaneously, a collection of plants was performed in different ecotopes, in order to make an extensive inventory of the pharmacopoeia.

RESULTS

For the Chayahuita, cutaneous (CL) and muco-cutaneous leishmaniasis (MCL) are considered as diseases of their own, with specific names, aetiologies, mode of transmission. Regarding CL, Chayahuita people consider that the humid characteristic of the skin ulcer is a discriminative fact orienting the diagnostic forTa'ta' (leishmaniasis). Forty-six different species were designated useful against LC and /or MCL (29 species by means of the questionnaire and 27 species when collecting in different ecotopes). Thirty-seven extracts corresponding to 31 species used medicinally were screened in vitro against Leishmania amazonensis axenic amastigotes, assessing their viability by the reduction of tetrazolium salt (MTT). Six species displayed a good activity (10 microg/ml<IC50<20 microg/ml): an undetermined hemi-epiphytic Clusiaceae, Cybianthus anthuriophyllus Pipoly (Myrsinaceae), two Piper, Piper sanguineispicum Trel., and Piper loretoanum Trel. (Piperaceae), Desmodium axillare Sw. DC. (Fabaceae), and Clibadium sylvestre (Aubl.) Baill. (Asteraceae).

CONCLUSION

Perception of leishmaniasis, attitude, treatments and diet prohibitions still largely reflects traditional Chayahuita cosmovision, even if some tentative of bio-medical re-interpretation is arising.

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.