Novel 2,5-Diketopiperazines with In Vitro Activities against Protozoan Parasites of Tropical Diseases

Malaria, Chagas disease, and leishmaniasis are tropical diseases caused by protozoan parasites of the genera Plasmodium, Trypanosoma and Leishmania, respectively. These diseases constitute a major burden on public health in several regions worldwide, mainly affecting low-income populations in economically poor countries. Severe side effects of currently available drug treatments and the emergence of resistant parasites need to be addressed by the development of novel drug candidates. Natural 2,5-Diketopiperazines (2,5-DKPs) constitute N-heterocyclic secondary metabolites with a wide range of biological activities of medicinal interest. Its structural and physicochemical properties make the 2,5-DKP ring a versatile, peptide-like, and stable pharmacophore attractive for synthetic drug design. In the present work, twenty-three novel synthetic 2,5-DKPs, previously synthesized through the versatile Ugi multicomponent reaction, were assayed for their anti-protozoal activities against P. falciparum, T. cruzi, and L. infantum. Some of the 2,5-DKPs have shown promising activities against the target protozoans, with inhibitory concentrations (IC50) ranging from 5.4 to 9.5 µg/mL. The most active compounds also show low cytotoxicity (CC50), affording selectivity indices ≥ 15. Results allowed for observing a clear relationship between the substitution pattern at the aromatic rings of the 2,5-DKPs and their corresponding anti-Plasmodium activity. Finally, calculated drug-like properties of the compounds revealed points for further structure optimization of promising drug candidates.

2,5-Diketopiperazines via Intramolecular N-Alkylation of Ugi Adducts: A Contribution to the Synthesis, Density Functional Theory Study, X-ray Characterization, and Potential Herbicide Application

To investigate the herbicidal potential of 2,5-diketopiperazines (2,5-DKPs), we applied a known protocol to produce a series of 2,5-DKPs through intramolecular N-alkylation of Ugi adducts. However, the method was not successful for the cyclization of adducts presenting aromatic rings with some substituents at the ortho position. Results from DFT calculations showed that the presence of voluminous groups at the ortho position of a benzene ring results in destabilization of the transition structure. Lower activation enthalpies for the S_N2-type cyclization of Ugi adducts were obtained when bromine, instead of a chlorine anion, is the leaving group, indicating that the activation enthalpy for the cyclization step controls the formation of the 2,5-DKP. Some Ugi adducts and 2,5-DKPs formed crystals with suitable qualities for single-crystal X-ray diffraction data collection. Phytotoxic damage of some 2,5-DKPs on leaves of the weed Euphorbia heterophylla did not differ from those caused by the commercial herbicide diquat.

Tetanus vaccination in pregnant women: a systematic review and meta-analysis of the global literature

OBJECTIVES

This study aimed to determine the effect of several factors on the uptake of tetanus vaccination in pregnant women.

STUDY DESIGN

This is a systematic review and meta-analysis of the global literature.

METHODS

The search strategy was carried out in the EMBASE and MEDLINE (Pubmed) databases, without language restrictions. The databases were searched from the beginning until May 2020. Fixed and random effect models were applied according to the methodological heterogeneity between the included studies. The I² test was performed to assess the magnitude of the heterogeneity. The results were presented as a grouped odds ratio (OR) with a 95% confidence interval (CI) and a significance level of 0.05.

RESULTS

The initial search strategy generated 14,349 original articles. In total, 31 studies met all inclusion criteria and 20 articles were included in the meta-analysis. The grouped and subgroup analyses showed a significant association between tetanus vaccination and the following factors: higher number of prenatal visits (OR: 2.00; 95% CI: 1.17-3.42), higher maternal age (OR: 1.24, 95% CI: 1.02-1.50), being single (OR: 1.41; 95% CI: 1.20-1.65), professional vaccine guidance (OR: 9.00; 95% CI: 1.81-44.75) and uptake of influenza vaccine (OR: 5.87; 95% CI: 1.39-24.73).

CONCLUSIONS

The uptake of tetanus vaccine in pregnant women is associated with various factors. The identification of these factors is an important step towards the implementation of public health strategies aimed at improving immunisation against tetanus in pregnant women.