María V. Castelli

In Vitro Antifungal Evaluation and Structure-Activity Relationships of a New Series of Chalcone Derivatives and Synthetic Analogues, with Inhibitory Properties Against Polymers of the Fungal Cell Wall

Here we report the synthesis, in vitro antifungal evaluation and SAR study of 41 chalcones and analogues. In addition, all active structures were tested for their capacity of inhibiting Saccharomyces cerevisiae beta(1,3)-glucan synthase and chitin synthase, enzymes that catalyze the synthesis of the major polymers of the fungal cell wall.

In vitro antifungal activity of new series of homoallylamines and related compounds with inhibitory properties of the synthesis of fungal cell wall polymers

The synthesis, in vitro antifungal evaluation and SAR studies of 101 compounds of the 4-aryl-, 4-alkyl-, 4-pyridyl or -quinolinyl-4-N-arylamino-1-butenes series and related compounds, are reported here. Active structures showed to inhibit (1,3)-beta-D-glucan and mainly chitin synthases, enzymes that catalyze the synthesis of the major fungal cell wall polymers.

Novel antifungal agents: a patent review (2011 - present).

Introduction: Invasive fungal infections (IFI) have increased significantly over the past decades. The mortality rate of IFI is alarming, and early and accurate diagnosis is difficult. Most used antifungal drugs are not completely effective due to the development of increasing resistance and undesirable side effects which limit their use. In this scenario, new effective broad spectrum and safer antifungal drugs are urgently needed. Areas covered: This review summarizes the latest advances in the discovery of new antifungal compounds through the patents granted from 2011 to August 2013. In the 26 patents reviewed here, either derivatives of existing antifungal drugs or novel structures are included. New imidazoles, fluconazole analogs and adducts of azoles with 2,6-di-tert-butyl-4-methylphenol are described. The review also includes chitinases, β-1,3-D-glucan and chitin synthases inhibitors and novel structures. Expert opinion: In the patents reviewed here, progress has been made to accomplish at least one of the necessary requirements for the development of novel antifungal agents, such as broad spectrum of activity, more favorable pharmacokinetic profile, good bioavailability and low adverse effects. However, in vivo activity, mechanisms of action, drug–drug interactions and other aspects that make a compound a good antifungal agent need further development.

Activity of 8.O.4'-neolignans against Trypanosoma cruzi

The in vitro evaluation of a series of 8.O.4′-neolignans (in their ketone, alcohol, and acetylated forms) on the proliferation of Trypanosoma cruzi led to the detection of three compounds with interesting activities against T. cruzi epimastigotes. These compounds also inhibited the in vitro differentiation of epimastigotes to trypomastigotes. When tested against HeLa cells, the same compounds did not affect the cell vitality and showed a low influence on cell viability as measured by dimethylthiazol diphenyltetrazolium bromide reduction. The three phenylpropanoid moieties tested did not show any activity against T. cruzi. One of the tested compounds, compound 4 (3,4-methylenedioxi7-oxo-1′-allyl-3′,5′-dimethoxy-8.O.4′-neolignan) showed the best performance in both trypanocide and cytotoxic assays, suggesting that it should be considered as a leading structure for further research.

Trypanocidal Activity of Flavokawin B, a Component of Polygonum ferrugineum Wedd

The trypanocidal potential of the natural chalcone flavokawin B, which was isolated from the hexanic extract of Polygonum ferrugineum Wedd., is reported here. Although flavokawin B is widespread, this is the first report about its trypanocidal properties on both Trypanosoma cruzi (IC50 = 9.5 µM, IC50 = 34.7 µM benznidazol, Y strain) epimastigotes and Trypanosoma brucei (IC50 = 4.8 µM, IC50 = 6.4 µM pentamidine, 29-13 strain) procyclic forms, which was also corroborated on T. brucei strain 427 (IC50 = 6.2 µM). In order to learn more about its properties, unspecific cytotoxicity on Hep G2 cells was investigated as well as the trans-splicing inhibitory potential on T. brucei cells. The results shown here point to flavokawin B as a candidate in the search for new agents. It is also cheaper and less toxic than the available drugs to treat trypanosomiasis with a special focus on sleeping sickness disease.

Ascochyta blight: isolation, characterization, and development of a rapid method to detect inhibitors of the chickpea fungal pathogen Ascochyta rabiei

Ascochyta blight is the major disease attacking chickpea (Cicer arietinum) around the world. Since its first time report of isolation in Argentina in 2012, the pathogen has caused severe economic losses and has acquired a great importance. We report here the isolation of Ascochyta rabiei from infected chickpea beans cultivated in Santa Fe, Argentina; its identification by morphological analysis and molecular biology techniques based on internal transcribed spacer (ITS) sequence alignment, its biochemical characterization regarding the capacity to produce proteinase and phospholipase enzymes, and its antifungal susceptibility to common used antifungal agents. In order to detect new inhibitors for A. rabiei from natural sources, a bioautographic method was developed. From the screening method developed, we found that extracts from cultures of Aspergillus parasiticus are active against A. rabiei.

ATP hydrolysis-driven H+ translocation is stimulated by sulfate, a strong inhibitor of mitochondrial ATP synthesis

Sulfate is a partial inhibitor at low and a non-essential activator at high [ATP] of the ATPase activity of F1. Therefore, a catalytically-competent ternary F1•ATP•sulfate complex can be formed. In addition, the ANS fluorescence enhancement driven by ATP hydrolysis in submitochondrial particles is also stimulated by sulfate, clearly showing that the ATP hydrolysis in its presence is coupled to H+ translocation. However, sulfate is a strong linear inhibitor of the mitochondrial ATP synthesis. The inhibition was competitive (Ki=0.46 mM) with respect to Pi and mixed (Ki=0.60 and K′i=5.6 mM) towards ADP. Since it is likely that sulfate exerts its effects by binding at the Pi binding subdomain of the catalytic site, we suggest that the catalytic site involved in the H+ translocation driven by ATP hydrolysis has a more open conformation than the half-closed one (βHC), which is an intermediate in ATP synthesis. Accordingly, ATP hydrolysis is not necessarily the exact reversal of ATP synthesis.

Effects on Other Microorganisms

Sesquiterpene lactones (STLs) are natural and semisynthetic compounds displaying interesting biological activities, including antiprotozoal, anti-inflammatory, and cytotoxic among the most studied. Some compounds belonging to this group have recently been described as promising antimicrobial hits. In this chapter, the antifungal, antibacterial, and antiviral properties will be discussed, taking into account their basic chemical scaffolds.