Diterpenoids from Azorella compacta (Umbelliferae) active on Trypanosoma cruzi

Ethnopharmacology, Phytochemistry and Biological Activities of Native Chilean Plants

The native flora of Chile has unique characteristics due to the geographical situation of the country, with the vast desert in the North, Patagonia in the South, the Andean Mountains on the east and the Pacific Ocean on the west. This exclusivity is reflected in high concentrations of phytochemicals in the fruits and leaves of its native plants. Some examples are Aristotelia chilensis (Molina), Stuntz (maqui), Berberis microphylla G. Forst. (calafate), Peumus boldus Molina (boldo), Ribes magellanicum Poir. (Magellan currant), Ugni molinae Turcz. (murtilla), Rubus geoides Sm. (miñe miñe), Drimys winteri J.R.Forst. & G.Forst. (canelo), Luma apiculata (DC.) Burret (arrayán) distributed throughout the entire Chilean territory. Some of these Chilean plants have been used for centuries in the country's traditional medicine. The most recent studies of phytochemical characterization of parts of Chilean plants show a wide spectrum of antioxidant compounds, phenolic components, terpenoids and alkaloids, which have shown biological activity in both in vitro and in vivo studies. This manuscript covers the entire Chilean territory characterizing the phytochemical profile and reporting some of its biological properties, focusing mainly on antioxidant, anti-inflammatory, antimicrobial, chemopreventive and cytotoxic activity, and potential against diabetes, metabolic syndrome and gastrointestinal disorders.

Mulinane- and Azorellane-Type Diterpenoids: A Systematic Review of Their Biosynthesis, Chemistry, and Pharmacology

Mulinane- and azorellane-type diterpenoids have unique tricyclic fused five-, six-, and seven-membered systems and a wide range of biological properties, including antimicrobial, antiprotozoal, spermicidal, gastroprotective, and anti-inflammatory, among others. These secondary metabolites are exclusive constituents of medicinal plants belonging to the Azorella, Laretia, and Mulinum genera. In the last 30 years, more than 95 mulinanes and azorellanes have been reported, 49 of them being natural products, 4 synthetics, and the rest semisynthetic and biotransformed derivatives. This systematic review highlights the biosynthetic origin, the chemistry, and the pharmacological activities of this remarkably interesting group of diterpenoids.

Crystal structure of methyl 8-hydroxy-3-isopropyl-5a,8-dimethyl-2,3,4,5,5a,6,7,8,10a,10b-decahydrocyclohepta[e]indene-3a(1H)-carboxylate, C21H34O3

C21H34O3, orthorhombic, P212121 (no. 19), a = 7.5420(7) Å, b = 11.6929(11) Å, c = 22.657(2) Å, V = 1998.1(3) Å3, Z = 4, R gt (F) = 0.0383, wR ref (F 2 ) = 0.113, T = 293(2) K.

A new mulinane diterpenoid from the cushion shrub Azorella compacta growing in Perú

Background:

Azorella compacta is a rare yellow-green compact resinous cushion shrub growing from the high Andes of southern Perú to northwestern Argentina, and which is a producer of biologically active and unique diterpenoids.

Objective:

This study investigated the secondary metabolites present in a Peruvian sample of Azorella compacta and the evaluation of gastroprotective activity of the isolated compounds in a gastric- induced ulcer model in mice.

Material and Methods:

Six secondary metabolites (diterpenoids 1-6) present in the dichloromethane (DCM) extract of A. compacta growing in Perú were isolated by a combination of Sephadex LH-20 permeation and silica gel chromatography and their chemical structures were elucidated by spectroscopic methods (NMR) and molecular modeling. The gastroprotective activity of the new compound 1 was evaluated on the HCl/EtOH-induced gastric lesion model in mice and compared to the activity showed by the known compounds.

Results:

A new mulinane diterpene along with five known diterpenoids have been isolated from a Peruvian sample of A. compacta and the gastroprotective results show that compound 1 is less active than the other known mulinane diterpenoids isolated.

Conclusions:

A. compacta growing in Perú showed the presence of the new mulinane 1, which was poorly active in the HCl/EtOH-induced gastric lesion model in mice. Indeed, the activity was lower than other diterpenoids (2-6) showing an oxygenated function at C-16 or/and C-20, which confirm the role of an oxygenated group (OH or carboxylic acid) for the gastroprotective activity of mulinane compounds.

A cytoplasmic new catalytic subunit of calcineurin in Trypanosoma cruzi and its molecular and functional characterization

Parasitological cure for Chagas disease is considered extremely difficult to achieve because of the lack of effective chemotherapeutic agents against Trypanosoma cruzi at different stages of infection. There are currently only two drugs available. These have several limitations and can produce serious side effects. Thus, new chemotherapeutic targets are much sought after. Among T. cruzi components involved in key processes such as parasite proliferation and host cell invasion, Ca(2+)-dependent molecules play an important role. Calcineurin (CaN) is one such molecule. In this study, we cloned a new isoform of the gene coding for CL strain catalytic subunit CaNA (TcCaNA2) and characterized it molecularly and functionally. There is one copy of the TcCaNA2 gene per haploid genome. It is constitutively transcribed in all T. cruzi developmental forms and is localized predominantly in the cytosol. In the parasite, TcCaNA2 is associated with CaNB. The recombinant protein TcCaNA2 has phosphatase activity that is enhanced by Mn(2+)/Ni(2+). The participation of TcCaNA2 in target cell invasion by metacyclic trypomastigotes was also demonstrated. Metacyclic forms with reduced TcCaNA2 expression following treatment with morpholino antisense oligonucleotides targeted to TcCaNA2 invaded HeLa cells at a lower rate than control parasites treated with morpholino sense oligonucleotides. Similarly, the decreased expression of TcCaNA2 following treatment with antisense morpholino oligonucleotides partially affected the replication of epimastigotes, although to a lesser extent than the decrease in expression following treatment with calcineurin inhibitors. Our findings suggest that the calcineurin activities of TcCaNA2/CaNB and TcCaNA/CaNB, which have distinct cellular localizations (the cytoplasm and the nucleus, respectively), may play a critical role at different stages of T. cruzi development, the former in host cell invasion and the latter in parasite multiplication.

Further mulinane diterpenoids from Azorella compacta

OBJECTIVES

The chemical study of a dichloromethane extract from Azorella compacta was directed to the isolation of characteristic mulinane and azorellane diterpenoids in order to determine their gastroprotective activity.

METHODS

Usual chromatographic techniques on the extract led to the isolation of 12 compounds, which were identified by their spectroscopic properties. The HCl/ethanol-induced gastric lesions model in mice was used to determine the gastroprotective activity.

KEY FINDINGS

The new diterpenoids, 13β-hydroxymulinane (1), mulin-11,13-dien-20-ol (2), 13α-methoxyazorellanol (3) and mulin-11,13-dien-18-acetoxy-16,20-dioic acid (12) were isolated from A. compacta. The known diterpenoids mulin-11,13-dien-20-oic acid (4), 13α-hydroxyazorellane (5), 13β-hydroxyazorellane (6), mulinic acid (7), mulinolic acid (8) and azorellanol (9), and the aromatic compounds 5,7-dihydroxychromone (10) and isoflavonoid biochanin A (11), were also obtained from the extract. Compounds 6, 9 and 12 at 20 mg/kg reduced gastric lesions by 69%, 71% and 73%, respectively, being statistically similar to lansoprazole at the same dose.

CONCLUSIONS

The results corroborate the intraspecific chemical variations detected previously in specimens of A. compacta collected at different Chilean latitudes. A high concentration of azorellanol (9) could account in part for some of the therapeutic properties attributed to this species, in particular in ulcer treatment. Most of the mulinane and azorellane diterpenoids isolated in this study showed relevant gastroprotective activity at a low dose in the bioassay.

Antimicrobial activity of synthetic bornyl benzoates against Trypanosoma cruzi

We report here for the first time the in vitro effects of (1S,2R,4S)-1,7,7-trimethyl-bicyclo[2·2·1]heptan-2-yl-3',4',5'-trimethoxy benzoate (1) and (1S,2R,4S)-1,7,7-trimethyl-bicyclo[2·2·1]heptan-2-yl benzoate (2) on the growth and ultrastructure of Trypanosoma cruzi. These two synthetic compounds exerted an antiproliferative effect on the epimastigote forms of the parasite. The ICs(50/72h) of two synthetic L-bornyl benzoates, 1 and 2, was 10·1 and 12·8 μg/ml, respectively. Both compounds were more selective against epimastigotes than HEp-2 cells. Ultrastructural analysis revealed intense cytoplasmic vacuolization and the appearance of cytoplasmic materials surrounded by membranes. The treatment of peritoneal macrophages with compounds 1 and 2 caused a significant decrease in the number of T. cruzi-infected cells. L-Bornyl benzoate derivatives may serve as a potential source for the development of more effective and safer chemotherapeutic agents against T. cruzi infections.

Essential oil of Azorella cryptantha collected in two different locations from San Juan Province, Argentina: chemical variability and anti-insect and antimicrobial activities

The essential oils (EOs) of two populations of Azorella cryptantha (Clos) Reiche, a native species from San Juan Province, were obtained by hydrodistillation in a Clevenger-type apparatus and characterized by GC-FID and GC/MS analyses. The compounds identified amounted to 92.3 and 88.7% of the total oil composition for A. cryptantha from Bauchaceta (Ac-BAU) and Agua Negra (Ac-AN), respectively. The EO composition for the two populations was similar, although with differences in the identity and content of the main compounds and also in the identity of minor components. The main compounds of the Ac-BAU EO were α-pinene, α-thujene, sabinene, δ-cadinene, δ-cadinol, trans-β-guaiene, and τ-muurolol, while α-pinene, α-thujene, β-pinene, γ-cadinene, τ-cadinol, δ-cadinene, τ-muurolol, and a not identified compound were the main constituents of the Ac-AN EO, which also contained 3.0% of oxygenated monoterpenes. The repellent activity on Triatoma infestans nymphs was 100 and 92% for the Ac-AN and Ac-BAU EOs, respectively. Regarding the toxic effects on Ceratitis capitata, the EOs were very active with LD(50) values lower than 11 μg/fly. The dermatophytes Microsporum gypseum, Trichophyton rubrum, and T. mentagrophytes and the bacterial strains Escherichia coli LM(1), E. coli LM(2), and Yersinia enterocolitica PI were more sensitive toward the Ac-AN EO (MIC 125 μg/ml) than toward the Ac-BAU EO. This is the first report on the composition of A. cryptantha EO and its anti-insect and antimicrobial properties.

Trypanocide, cytotoxic, and antifungal activities of Momordica charantia

CONTEXT

Chagas disease, caused by Trypanosoma cruzi, is a public health problem. Currently, chemotherapy is the only available treatment for this disease, and the drugs used, nifurtimox and benzonidazol, present high toxicity levels. An alternative for replacing these drugs are natural extracts from Momordica charantia L. (Cucurbitaceae) used in traditional medicine because of their antimicrobial and biological activities.

OBJECTIVE

In this study, we evaluated the extract of M. charantia for its antiepimastigote, antifungal, and cytotoxic activities.

MATERIALS AND METHODS

An ethanol extract of leaves from M. charantia was prepared. To research in vitro antiepimastigote activity, T. cruzi CL-B5 clone was used. Epimastigotes were inoculated at a concentration of 1 × 10(5) cells/mL in 200 µl tryptose-liver infusion. For the cytotoxicity assay, J774 macrophages were used. The antifungal activity was evaluated by microdilution using strains of Candida albicans, Candida tropicalis, and Candida krusei.

RESULTS

The effective concentration capable of killing 50% of parasites (IC(50)) was 46.06 µg/mL. The minimum inhibitory concentration (MIC) was ≤ 1024 µg/mL. Metronidazole showed a potentiation of its antifungal effect when combined with an extract of M. charantia.

CONCLUSIONS

Our results indicate that M. charantia could be a source of plant-derived natural products with antiepimastigote and antifungal-modifying activity with moderate toxicity.

17-Acetoxymulinic acid

The title compound, [systematic name: 5a-acet­oxy­methyl-3-isopropyl-8-methyl-1,2,3,3a,4,5,5a,6,7,10,10a,10b-dodeca­hydro-7,10-endo-epidi­oxy­cyclo­hepta­[e]indene-3a-carb­oxy­lic acid], C₂₂H₃₂O₆ (I), is closely related to methyl 5a-acet­oxy­methyl-3-isopropyl-8-methyl-1,2,3,3a,4,5,5a,6,7,10,10a,10b-dodeca­hydro-7,10-endo-epidi­oxy­cyclo­hepta­[e]indene-3a-carboxyl­ate, (II) [Brito et al., (2008 ▶). Acta Cryst. E64, o1209]. There are two mol­ecules in the asymmetric unit, which are linked by two strong intra­molecular O—H⋯O hydrogen bonds with graph-set motif R₂²(8). In both (I) and (II), the conformation of the three fused rings are almost identical. The five-membered ring has an envelope conformation, the six-membered ring has a chair conformation and the seven-membered ring has a boat conformation. The most obvious differences between the two compounds is the observed disorder of the acet­oxy­methyl fragments in both mol­ecules of the asymmetric unit of (I). This disorder is not observed in (II). The crystal structure and the molecular conformation is stabilized by intermolecular C—H⋯O hydrogen bonds. The ability to form hydrogen bonds is different in the two compounds. The crystal studied was a non-merohedral twin, the ratio of the twin components being 0.28 (1):0.72 (1)

Trypanocidal and antifungal activities of p-hydroxyacetophenone derivatives from Calea uniflora (Heliantheae, Asteraceae)

The dichloromethane extract of underground parts of Calea uniflora (Heliantheae, Asteraceae) exhibited trypanocidal and antifungal activities. Four p-hydroxyacetophenone derivatives were isolated as the main compounds: 2-senecioyl-4-(hydroxyethyl)-phenol (1), 2-senecioyl-4-(angeloyloxy-ethyl)-phenol (2), and two new derivatives, 2-senecioyl-4-(methoxyethyl)-phenol (3) and 2-senecioyl-4-(pentadecanoyloxyethyl)-phenol (4). 1 and 4 were active towards Trypanosoma cruzi trypomastigotes, reducing their number by 70 and 71% at 500 μg mL−1, whereas 2 and 3 were inactive. All the compounds tested showed antifungal activity with minimal inhibitory concentration values between 500 and 1000 μg mL−1 against pathogenic Candida spp. and dermatophytes. The isolation, structure elucidation, NMR spectral assignments and bioactivity results of these compounds are reported.

An orthorhombic polymorph of mulinic acid

The title compound [systematic name: (3S,3aS,10bR)-3-isopropyl-5a,8-dimethyl-2,3,4,5,5a,6,7,10,10a,10b-deca­hydro-endo-epidioxy­cyclo­hepta­[e]indene-3a(1H)-carboxylic acid], C₂₀H₃₀O₄, is a polymorphic form of a previously reported structure [Loyola et al. (1990 ▶). Tetra­hedron, 46, 5413–5420]. The newly found ortho­rhom­bic polymorph crystallizes in P2₁2₁2₁ with two mol­ecules in the asymmetric unit. The mol­ecules are linked into discrete D(2) chains by simple O—H⋯O inter­actions. There are only slight variations in the mol­ecular geometry and supra­molecular organization in the crystal structures of the two polymorphs. The densities are 1.145 (monoclinic, P2₁) and 1.155 Mg m⁻³ (ortho­rhom­bic, P2₁2₁2₁).

Microbial transformation of the diterpene mulin-11,13-dien-20-oic acid by Mucor plumbeus

Two new mulinane-type derivatives: 16-hydroxy mulin-11,13-dien-20-oic (2) acid and 7alpha,16-dihydroxy mulin-11,13-dien-20-oic (3) acid were obtained by microbial transformation of mulin-11,13-dien-20-oic acid (1), along with tyrosol (4) using liquid cultures of Mucor plumbeus. The latter compound has not been previously identified in the genus Mucor. Structural elucidation of these metabolites was achieved using 1D- and 2D-NMR spectroscopy.

(3S,3aS,5aS,7S,8S,10aS,10bR)-7,8-Dihydroxy-3-isopropyl-5a,8-dimethyl-2,3,4,5,5a,6,7,8,10a,10b-decahydrocyclohepta[e]indene-3a(1H)-carboxylic acid

The mol­ecule of the title compound, C₂₀H₃₂O₄, is built up from three fused five-membered, six-membered and seven-membered rings. The five-membered ring has an envelope conformation, whereas the six- and seven-membered rings have chair conformations. The crystal structure is stabilized by strong inter­molecular O—H⋯O hydrogen bonds, forming a three-dimensional network. The absolute configuration was assigned on the basis of earlier chemical studies.

Methyl 5a-acetoxy-methyl-3-isopropyl-8-methyl-1,2,3,3a,4,5,5a,6,7,10,10a,10b-dodeca-hydro-7,10-endo-epidioxy-cylohepta-[e]indene-3a-carboxyl-ate

The mol­ecule of the title compound, C₂₃H₃₄O₆, is built up from three fused carbocycles, one five-membered, one six-membered and one seven-membered. The five-membered ring has an envelope conformation, whereas the six-membered ring has a perfect chair conformation and the seven-membered ring has a boat conformation. Intra­molecular C—H⋯O hydrogen bonds together with van der Waals inter­actions stabilize the mol­ecular conformation.

Azorellane diterpenoids fromLaretia acaulisinhibit nuclear factor-kappa B activity

Transcription factor NF-kappaB plays a key role in the inducible expression of genes mediating proinflammatory effects, and is thus an important target for the development of antiinflammatory drugs. Laretia acaulis (Cav.) Gill et Hook (Apiaceae) is a medicinal plant used in the high Andes mountains for different ailments such as diabetes, inflammation and for general pain. In addition to the known azorellanol (2) and 7-deacetylazorellanol (4), 13-epiazorellanol (1) was also isolated from the aerial part of this plant. Its structure was based on spectroscopic comparison with azorellanol (2) and by chemical characterization. While compounds 2 and 4 showed potent anti-NF-kappaB activity by targeting the activity of the IkappaBalpha kinase, compound 1 was completely inactive highlighting the importance of position 13 in the biological activities of this class of tetracyclic diterpenoids.

Bioactive peroxides as potential therapeutic agents

Present review describes research on more than 280 natural anticancer agents isolated from terrestrial and marine sources and synthetic biologically active peroxides. Intensive searches for new classes of pharmacologically potent agents produced by terrestrial and marine organisms have resulted in the discovery of dozens of compounds possessing high cytotoxic, antibacterial, antimalarial, and other activities as an important source of leads for drug discovery.

Mode of action of natural and synthetic drugs against Trypanosoma cruzi and their interaction with the mammalian host

Current knowledge of the biochemistry of Trypanosoma cruzi has led to the development of new drugs and the understanding of their mode of action. Some trypanocidal drugs such as nifurtimox and benznidazole act through free radical generation during their metabolism. T. cruzi is very susceptible to the cell damage induced by these metabolites because enzymes scavenging free radicals are absent or have very low activities in the parasite. Another potential target is the biosynthetic pathway of glutathione and trypanothione, the low molecular weight thiol found exclusively in trypanosomatids. These thiols scavenge free radicals and participate in the conjugation and detoxication of numerous drugs. Inhibition of this key pathway could render the parasite much more susceptible to the toxic action of drugs such as nifurtimox and benznidazole without affecting the host significantly. Other drugs such as allopurinol and purine analogs inhibit purine transport in T. cruzi, which cannot synthesize purines de novo. Nitroimidazole derivatives such as itraconazole inhibit sterol metabolism. The parasite's respiratory chain is another potential therapeutic target because of its many differences with the host enzyme complexes. The pharmacological modulation of the host's immune response against T. cruzi infection as a possible chemotherapeutic target is discussed. A large set of chemicals of plant origin and a few animal metabolites active against T. cruzi are enumerated and their likely modes of action are briefly discussed.

A novel icetexane diterpene, 5-epi-icetexone from Salvia gilliessi is active against Trypanosoma cruzi

In this work the effect of a novel compound, 5-epi-icetexone (ICTX) obtained from Salvia gilliessi Benth. (Labiatae), is studied on cultured epimastigotes of Trypanosoma cruzi (Tulahuen). It was found that the compound exerts an antiproliferative effect on the parasites at concentrations between 2.8 and 4.2 microM, and similar sensitivity in other strains (Dm28c, CL-Brener and Y-strain). The compound was deleterious at concentrations higher than 4.2 microM, with an estimated IC50 of 6.5+/-0.75 microM, but with low cytotoxicity to mammalian cells. These effects were irreversible, even at short times of exposure to the drug. In solution, ICTX showed to be stable for at least 96 h at 29 degrees C. With cytostatic dose a little percentage of parasites was resistant to the action of ICTX, and they continued growing although with different kinetic. By electron transmission microscopy, at dose of 4.2 microM an external vesiculization was observed on the first day of exposure to the compound, but the parasite cytoplasm became plenty of vacuoles and exhibited nuclear disorganization from the second day of exposure. It was concluded that ICTX is active against T. cruzi and may act by multiple mechanisms. In future, this novel icetexane diterpene may be a good candidate for therapeutic use against Chagas' disease.

Antichagasic activity of komaroviquinone is due to generation of reactive oxygen species catalyzed by Trypanosoma cruzi old yellow enzyme

A novel potent trypanocidal diterpene, komaroviquinone, was reduced by Trypanosoma cruzi old yellow enzyme (TcOYE) to its semiquinone radical. The reductase activity in trypanosome lysates was completely immunoabsorbed by anti-TcOYE antibody. Since TcOYE is expressed throughout the T. cruzi life cycle, komaroviquinone is an interesting candidate for developing new antichagasic drugs.

In vitro evaluation of trypanocidal activity in plants used in Argentine traditional medicine

Thirty-two organic and aqueous extracts, belonging to 12 Argentine medicinal plants were tested for their in vitro trypanocidal activity on epimastigote forms of Trypanosoma cruzi. Among the selected species, the organic extracts of Ambrosia scabra, Ambrosia tenuifolia, Baccharis spicata, Eupatorium buniifolium, Lippia integrifolia, Mulinum spinosum and Satureja parvifolia, and the aqueous extracts of E. buniifolium, L. integrifolia, M. spinosum and S. parvifolia showed trypanocidal activity with a percentage of growth inhibition higher than 70% at a concentration of 100 microg/ml.

Experimental antihyperglycemic effect of diterpenoids of llaretaAzorella compacta (Umbelliferae) Phil in rats

Aqueous or ethanol infusions of Azorella compacta (llareta) in common with many other plants have been used as antidiabetic in the popular medicine in the altiplanic region of Chile. In order to determine if the diterpenic compounds chemically elucidated and isolated from this plant are responsible for this effect, streptozotocin diabetic rats (507 +/- 67 mg/mL glucose) were injected with two injections of diterpenic compounds mulinolic acid, azorellanol, and mulin-11,13-dien-20-oic acid at 180 mg/mL. Glycemia of animals treated with mulinolic acid and azorellanol was decreased to 243 +/- 2 and 247 +/- 14 mg/mL respectively, values very close to those reached by chlorpropamide injection used in controls. After 3 h treatment with mulin-11,13-dien-20-oic acid no effect was detected. The blood serum insulin in diabetic rats (146 +/- 58 pg/mL) was lower than in control rats. After injection of azorellanol, insulin was elevated to 247 +/- 23 pg/mL but with mulinolic acid, insulin was not changed. The antihyperglycemic effect of these compounds may explain the effectiveness of llareta in popular medicine. Because of the similarity to the hypoglycemic medication chlorpropamide, azorellanol could be acting on the beta cells of pancreatic islets, while mulinolic acid may act upon glucose utilization or production in the liver.