Diacetal Ditellurides as Highly Active and Selective Antiparasitic Agents toward Leishmania amazonensis

Small molecules containing chalcogen elements (S, Se, Te) as new warhead to fight neglected tropical diseases

Neglected tropical diseases (NTDs) encompass a group of infectious diseases with a protozoan etiology, high incidence, and prevalence in developing countries. As a result, economic factors constitute one of the main obstacles to their management. Endemic countries have high levels of poverty, deprivation and marginalization which affect patients and limit their access to proper medical care. As a matter of fact, statistics remain uncollected in some affected areas due to non-reporting cases. World Health Organization and other organizations proposed a plan for the eradication and control of the vector, although many of these plans were halted by the COVID-19 pandemic. Despite of the available drugs to treat these pathologies, it exists a lack of effectiveness against several parasite strains. Treatment protocols for diseases such as American trypanosomiasis (Chagas disease), leishmaniasis, and human African trypanosomiasis (HAT) have not achieved the desired results. Unfortunately, these drugs present limitations such as side effects, toxicity, teratogenicity, renal, and hepatic impairment, as well as high costs that have hindered the control and eradication of these diseases. This review focuses on the analysis of a collection of scientific shreds of evidence with the aim of identifying novel chalcogen-derived molecules with biological activity against Chagas disease, leishmaniasis and HAT. Compounds illustrated in each figure share the distinction of containing at least one chalcogen element. Sulfur (S), selenium (Se), and tellurium (Te) have been grouped and analyzed in accordance with their design strategy, chemical synthesis process and biological activity. After an exhaustive revision of the related literature on S, Se, and Te compounds, 183 compounds presenting excellent biological performance were gathered against the different causative agents of CD, leishmaniasis and HAT.

Multicomponent Reaction of Isocyanide, Ditelluride, and Mn(III) Carboxylate: Synthesis of N-Acyl Tellurocarbamate

A multicomponent reaction of isocyanides, ditellurides and manganese(III) carboxylates under mild reaction conditions leads to the synthesis of various N-acyl tellurocarbamates. This method demonstrates good functional tolerance and broad substrate scope and, as a result, is especially suitable for the postfunctionalization of complicated molecules such as drugs. The given method can be further extended to the synthesis of selenocarbamates.

Synthesis of Tellurium Oxide (TeO2) Nanorods and Nanoflakes and Evaluation of Its Efficacy Against Leishmania major In Vitro and In Vivo

PURPOSE

Today, the use of natural products and nanostructures has increased. Given the reports on beneficial effects of various organotellurane compounds on types of visceral leishmaniasis, we decided to investigate the effect of TeO₂ NPs on Leishmania major (L. major). Tellurium can cause cell apoptosis in cancer cells without activating the caspase-pathway.

METHODS

TeO₂ NPs at first synthesized and the structure was checked by XRD, SEM and EDS tests. The cytotoxic effect of TeO₂ NPs against L. major promastigotes, amastigotes and macrophages was assessed by MTT test or counting. The possible apoptosis of L. major by TeO₂ NPs was evaluated by flow cytometry test. For in vivo assay, the lesions of infected BALB/c mice with L. major promastigotes were treated with TeO₂ NPs, then the lesion size and survival rate were evaluated.

RESULTS

The synthesis of TeO₂ with tetragonal structure was confirmed by XRD. The combination of nanorods and nanoflakes and the presence of Te were proven by SEM and EDS, respectively. According the effects of nanoparticle on promastigotes and amastigotes, the IC₅₀ values of TeO₂ after 72 h of incubation were 15.13 and 52.22 µg/ml, respectively. TeO₂ NPs induced apoptosis in about 41% of promastigotes. The ulcer greatly healed and survival rate was higher in treated mice compared to those in control group.

CONCLUSION

Based on the data, favorable anti-leishmanial properties were observed by using TeO₂ NPs. TeO₂ NPs have cytotoxic impacts on L. major promastigotes and amastigotes in vitro and in vivo and may be regarded as a therapy option.

Unexpected Ethyltellurenylation of Epoxides with Elemental Tellurium under Lithium Triethylborohydride Conditions

The one-pot multistep ethyltellurenylation reaction of epoxides with elemental tellurium and lithium triethylborohydride is described. The reaction mechanism was experimentally investigated. Dilithium ditelluride and triethyl borane, formed from elemental tellurium and lithium triethylborohydride, were shown to be the key species involved in the reaction mechanism. Epoxides undergo ring-opening reaction with dilithium ditelluride to afford β-hydroxy ditellurides, which are sequentially converted into the corresponding β-hydroxy-alkyl ethyl tellurides by transmetalation with triethyl borane, reasonably proceeding through the SH2 mechanism.

Synthesis of Tellurium-Containing π-Extended Aromatics with Room-Temperature Phosphorescence

A synthesis of tellurium-embedded π-extended aromatics from tellurium powder and readily available cyclic diaryliodonium salts has been developed. The versatility of this method has been demonstrated by the synthesis of various functionalized dibenzotellurophenes (DBTe's), a ladder-type π-system, and a heterosumanene. These compounds demonstrated good air/moisture stability and high thermal stability. Remarkably, many DBTe's exhibited interesting tunable room-temperature phosphorescence (RTP) in the solid state.