Trypanocidal and Anti-Inflammatory Effects of Three ent-Kaurane Diterpenoids from Gymnocoronis spilanthoides var. subcordata (Asteraceae).

Chagas disease, caused by the protozoan Trypanosoma cruzi, affects 6-7 million people worldwide. The dichloromethane extract obtained from the aerial parts of Gymnocoronis spilanthoides var subcordata showed trypanocidal activity in vitro. The fractionation of the dewaxed organic extract via column chromatography led to the isolation of three diterpenoids: ent-9α,11α-dihydroxy-15-oxo-kaur-16-en-19-oic acid or adenostemmoic acid B, (16R)-ent-11α-hydroxy-15-oxokauran-19-oic acid and ent-11α-hydroxy-15-oxo-kaur-16-en-19-oic acid. These compounds showed IC50 values of 10.6, 15.9 and 4.8 µM against T. cruzi epimastigotes, respectively. When tested against amastigotes, the diterpenoids afforded IC50 values of 6.1, 19.5 and 60.6 µM, respectively. The cytotoxicity of the compounds was tested on mammalian cells using an MTT assay, resulting in CC50s of 321.8, 23.3 and 14.8 µM, respectively. The effect of adenostemmoic acid B on T. cruzi was examined at the ultrastructural level using transmission microscopy. Treatment with 20 µM for 48 h stimulated the formation of abnormal cytosolic membranous structures in the parasite. This compound also showed an anti-inflammatory effect in murine macrophages stimulated with LPS and other TLR agonists. Treatment of macrophages with adenostemmoic acid B was able to reduce TNF secretion and nitric oxide production, while increasing IL-10 production. The combination of adenostemmoic acid B with benznidazole resulted in greater inhibition of NF-kB and a decrease in nitrite concentration. The administration of adenostemmoic acid B to mice infected with trypomastigotes of T. cruzi at the dose of 1 mg/kg/day for five days produced a significant decrease in parasitemia levels and weight loss. Treatment with the association with benznidazole increased the survival time of the animals. In view of these results, adenostemmoic acid B could be considered a promising candidate for further studies in the search for new treatments for Chagas disease.

Oxonitrogenated Derivatives of Eremophilans and Eudesmans: Antiproliferative and Anti-Trypanosoma cruzi Activity.

Cancer is one of the most important causes of death worldwide. Solid tumors represent the vast majority of cancers (>90%), and the chemotherapeutic agents used for their treatment are still characterized by variable efficacy and toxicity. Sesquiterpenes are a group of natural compounds that have shown a wide range of biological activities, including cytotoxic and antiparasitic activity, among others. The antiproliferative activity of natural sesquiterpenes, tessaric acid, ilicic acid, and ilicic alcohol and their semisynthetic derivatives against HeLa, T-47D, WiDr, A549, HBL-100, and SW1573 cell lines were evaluated. The effect of the compounds on Trypanosoma cruzi epimastigotes was also assessed. The selectivity index was calculated using murine splenocytes. Derivatives 13 and 15 were the most antiproliferative compounds, with GI50 values ranging between 5.3 (±0.32) and 14 (±0.90) µM, in all cell lines tested. The presence of 1,2,3-triazole groups in derivatives 15−19 led to improvements in activity compared to those corresponding to the starting natural product (3), with GI50 values ranging between 12 (±1.5) and 17 (±1.1) µM and 16 being the most active compound. In relation to the anti-T. cruzi activity, derivatives 7 and 16 obtained from tessaric acid and ilicic acid were among the most active and selective compounds with IC50 values of 9.3 and 8.8 µM (SI = 8.0 and 9.4), respectively.

Stevia Genus: Phytochemistry and Biological Activities Update.

The Stevia genus (Asteraceae) comprises around 230 species, distributed from the southern United States to the South American Andean region. Stevia rebaudiana, a Paraguayan herb that produces an intensely sweet diterpene glycoside called stevioside, is the most relevant member of this genus. Apart from S. rebaudiana, many other species belonging to the Stevia genus are considered medicinal and have been popularly used to treat different ailments. The members from this genus produce sesquiterpene lactones, diterpenes, longipinanes, and flavonoids as the main types of phytochemicals. Many pharmacological activities have been described for Stevia extracts and isolated compounds, antioxidant, antiparasitic, antiviral, anti-inflammatory, and antiproliferative activities being the most frequently mentioned. This review aims to present an update of the Stevia genus covering ethnobotanical aspects and traditional uses, phytochemistry, and biological activities of the extracts and isolated compounds.

Sesquiterpene Lactones and Diterpenes: Promising Therapeutic Candidates for Infectious Diseases, Neoplasms and Other Chronic Disorders.

Nature is an important source for the discovery of new bioactive compounds [...].

Preparation of Sesquiterpene Lactone Derivatives: Cytotoxic Activity and Selectivity of Action.

Cancer is one of the most important causes of death worldwide. Solid tumors represent the great majority of cancers (>90%) and the chemotherapeutic agents used for their treatment are still characterized by variable efficacy and toxicity. Sesquiterpene lactones are a group of naturally occurring compounds that have displayed a diverse range of biological activities including cytotoxic activity. A series of oxygenated and oxy-nitrogenated derivatives (4⁻15) from the sesquiterpene lactones cumanin (1), helenalin (2), and hymenin (3) were synthesized. The silylated derivatives of helenalin, compounds 13 and 14, were found to be the most active against tumor cell lines, with GI50 values ranging from 0.15 to 0.59 µM. The ditriazolyl cumanin derivative (11) proved to be more active and selective than cumanin in the tested breast, cervix, lung, and colon tumor cell lines. This compound was the least toxic against splenocytes (CC50 = 524.1 µM) and exhibited the greatest selectivity on tumor cell lines. This compound showed a GI50 of 2.3 µM and a SI of 227.9 on WiDr human colon tumor cell lines. Thus, compound 11 can be considered for further studies and is a candidate for the development of new antitumor agents.

Primary targets of the sesquiterpene lactone deoxymikanolide on Trypanosoma cruzi.

BACKGROUND: Deoxymikanolide is a sesquiterpene lactone isolated from Mikania micrantha and M. variifolia which, has previously demonstrated in vitro activity on Trypanosoma cruzi and in vivo activity on an infected mouse model. PURPOSE: Based on these promising findings, the aim of this study was to investigate the mechanism of action of this compound on different parasite targets. METHODS: The interaction of deoxymikanolide with hemin was examined under reducing and non- reducing conditions by measuring modifications in the Soret absorption band of hemin; the thiol interaction was determined spectrophotometrically through its reaction with 5,5'-dithiobis-2-nitrobenzoate in the presence of glutathione; activity on the parasite antioxidant system was evaluated by measuring the activity of the superoxide dismutase and trypanothione reductase enzymes, together with the intracellular oxidative state by flow cytometry. Superoxide dismutase and trypanothione reductase activities were spectrophotometrically tested. Cell viability, phosphatidylserine exposure and mitochondrial membrane potential were assessed by means of propidium iodide, annexin-V and rhodamine 123 staining, respectively; sterols were qualitatively and quantitatively tested by TLC; ultrastructural changes were analyzed by transmission electron microscopy. Autophagic cells were detected by staining with monodansylcadaverine. RESULTS: Deoxymikanolide decreased the number of reduced thiol groups within the parasites, which led to their subsequent vulnerability to oxidative stress. Treatment of the parasites with the compound produced a depolarization of the mitochondrial membrane even though the plasma membrane permeabilization was not affected. Deoxymikanolide did not affect the intracellular redox state and so the mitochondrial dysfunction produced by this compound could not be attributed to ROS generation. The antioxidant defense system was affected by deoxymikanolide at twenty four hours of treatment, when both an increased oxidative stress and decreased activity of superoxide dismutase and trypanothione reductase (40 and 60% respectively) were observed. Both the oxidative stress and mitochondrial dysfunction induce parasite death by apoptosis and autophagy. CONCLUSION: Based on our results, deoxymikanolide would exert its anti-T cruzi activity as a strong thiol blocking agent and by producing mitochondrial dysfunction.

Assessment of sesquiterpene lactones isolated from Mikania plants species for their potential efficacy against Trypanosoma cruzi and Leishmania sp.

Four sesquiterpene lactones, mikanolide, deoxymikanolide, dihydromikanolide and scandenolide, were isolated by a bioassay-guided fractionation of Mikania variifolia and Mikania micrantha dichloromethane extracts. Mikanolide and deoxymikanolide were the major compounds in both extracts (2.2% and 0.4% for Mikania variifolia and 21.0% and 6.4% for Mikania micrantha respectively, calculated on extract dry weight). Mikanolide, deoxymikanolide and dihydromikanolide were active against Trypanosoma cruzi epimastigotes (50% inhibitory concentrations of 0.7, 0.08 and 2.5 µg/mL, for each compound respectively). These sesquiterpene lactones were also active against the bloodstream trypomastigotes (50% inhibitory concentrations for each compound were 2.1, 1.5 and 0.3 µg/mL, respectively) and against amastigotes (50% inhibitory concentrations for each compound were 4.5, 6.3 and 8.5 µg/mL, respectively). By contrast, scandenolide was not active on Trypanosoma cruzi. Besides, mikanolide and deoxymikanolide were also active on Leishmania braziliensis promastigotes (50% inhibitory concentrations of 5.1 and 11.5 µg/mL, respectively). The four sesquiterpene lactones were tested for their cytotoxicity on THP 1 cells. Deoxymikanolide presented the highest selectivity index for trypomastigotes (SI = 54) and amastigotes (SI = 12.5). In an in vivo model of Trypanosoma cruzi infection, deoxymikanolide was able to decrease the parasitemia and the weight loss associated to the acute phase of the parasite infection. More importantly, while 100% of control mice died by day 22 after receiving a lethal T. cruzi infection, 70% of deoxymikanolide-treated mice survived. We also observed that this compound increased TNF-α and IL-12 production by macrophages, which could contribute to control T. cruzi infection.