Artichoke extracts with potential application in chemoprevention and inflammatory processes

Abstract The aim of this work is to study three cultivars of artichoke (Cynara cardunculus var. scolymus): Gauchito, Guri and Oro Verde in terms of their in vitro chemoprevention and anti-inflammatory properties. These cultivars show good productive performance. The phenolic composition of their fresh leaves and edible bracts was analyzed by high performance liquid chromatography and high resolution mass spectrometry (HPLC-HRMS), showing mainly caffeoylquinic acids and flavonoids. Caffeoylquinic acids were quantified and the highest content was found in Gauchito cultivar. In this cultivar, the content of dicaffeoylquinic acids in fresh bracts was six times higher than that in fresh leaves (10064.5 ± 378.3 mg/kg versus 1451.0 ± 209.3 mg/kg respectively). Luteolin flavonoids were detected in leaves. The extracts from fresh bracts and leaves were assessed in their in vitro bioactivity against human neuroblastoma cells (SH-SY5Y). Inhibition of SH-SY5Y cells proliferation by Gauchito and Guri leaf extracts (8 µg/mL) was higher than 50 %. The leaf extracts of the same cultivars showed an inhibitory effect on human interferon IFN-I, decreasing its activity 50% at 40 µg/mL. Interestingly, the bract extracts did not show in vitro bioactivity at these concentrations, nor did the pure compounds chlorogenic acid, cynarin, apigenin and luteolin (at 2 µg/mL). These results suggest that Gauchito and Guri leaf extracts have potential for human neuroblastoma chemoprevention and treatment of inflammatory processes.

Molecular Networks in Dynamic Multilevel Systems.

Dynamic multilevel systems can be assembled from molecular building blocks through two or more reversible reactions that form covalent bonds. Molecular networks of dynamic multilevel systems can exhibit different connectivities between nodes. The design and creation of molecular networks in multilevel systems require control of the crossed reactivity of the functional groups (how to connect nodes) and the conditions of the reactions (when to connect nodes). In recent years, the combination of orthogonal and communicating reactions, which can be simultaneous or individually activated, has produced a variety of systems that have given rise to macrocycles and cages, as well as molecular motors and multicomponent architectures on surfaces. A given set of reactions can lead to systems with unique responsiveness, compositions, and functions as a result of the relative reactivities. In this Concept article, different molecular networks from synthetic systems that can be produced by combinations of different reaction types are discussed. Moreover, applications of this chemistry are highlighted, and future perspectives are envisioned.

Discovery of a Biologically Active Bromodomain Inhibitor by Target-Directed Dynamic Combinatorial Chemistry.

Target-directed dynamic combinatorial chemistry (DCC) has emerged as a strategy for the identification of inhibitors of relevant therapeutic targets. In this contribution, we use this strategy for the identification of a high-affinity binder of a parasite target, the Trypanosoma cruzi bromodomain-containing protein TcBDF3. This protein is essential for viability of T. cruzi, the protozoan parasite that causes Chagas disease. A small dynamic library of acylhydrazones was prepared from aldehydes and acylhydrazides at neutral pH in the presence of aniline. The most amplified library member shows (a) high affinity for the template, (b) interesting antiparasitic activity against different parasite forms, and (c) low toxicity against Vero cells. In addition, parasites are rescued from the compound toxicity by TcBDF3 overexpression, suggesting that the toxicity of this compound is due to the TcBDF3 inhibition, i.e., the binding event that initially drives the molecular amplification is reproduced in the parasite, leading to selective toxicity.

Rewiring Chemical Networks Based on Dynamic Dithioacetal and Disulfide Bonds.

The control of the connectivity between nodes of synthetic networks is still largely unexplored. To address this point we take advantage of a simple dynamic chemical system with two exchange levels that are mutually connected and can be activated simultaneously or sequentially. Dithioacetals and disulfides can be exchanged simultaneously under UV light in the presence of a sensitizer. Crossover reactions between both exchange processes produce a fully connected chemical network. On the other hand, the use of acid, base or UV light connects different nodes allowing network rewiring.

Host Amplification in a Dithioacetal-Based Dynamic Covalent Library.

Molecular amplification in a dithioacetal-based dynamic library is described for the first time. The homatropine induced selection, amplification, and isolation of one cyclophane host demonstrates the utility of dithioacetal exchange for preparing responsive dynamic libraries. Nuclear magnetic resonance and isothermal titration calorimetry analysis suggest that the amplified macrocycle forms a 1:1 complex with the template. This is the first report about a host/guest system involving a dithioacetal cyclophane.

Dithioacetal Exchange: A New Reversible Reaction for Dynamic Combinatorial Chemistry.

Reversibility of dithioacetal bond formation is reported under acidic mild conditions. Its utility for dynamic combinatorial chemistry was explored by combining it with orthogonal disulfide exchange. In such a setup, thiols are positioned at the intersection of both chemistries, constituting a connecting node between temporally separated networks.

Two-stage amplification of receptors using a multilevel orthogonal/simultaneous dynamic combinatorial library.

Sequential activation of different reversible exchange reactions in a dynamic combinatorial library allows directed exploration of the chemical space: initially a macrocyclic scaffold is selected by the template and finally side chain and conformational constrains are introduced into such a scaffold.

Characterization of bifunctional sphingolipid Δ4-desaturases/C4-hydroxylases of trypanosomatids by liquid chromatography-electrospray tandem mass spectrometry.

Six genes encoding putative sphingolipid desaturases have been identified in trypanosomatid genomes: one in Trypanosoma brucei (TbSLdes protein), one in Trypanosoma cruzi (TcSLdes) and four in Leishmania major (LmSLdes1-4), tandemly arrayed on chromosome 26. The six amino acid sequences showed the three characteristic histidine boxes, with a long spacer between the first and second box, as in fungal desaturases and bifunctional desaturases/hydroxylases, to which they are phylogenetically related. We functionally characterized the trypanosomatid enzymes by their expression in Saccharomyces cerevisiae sur2Δ mutant, which lacks C4-hydroxylase activity. The sphingoid base profile (dinitrophenyl derivatives) of each yeast mutant transformed with each one of the different parasite genes was analyzed by HPLC, using a sur2Δ mutant expressing the Schyzosaccharomyces pombe sphingolipid desaturase (SpSLdes) as positive control. TbSLdes was capable of desaturating endogenous sphingolipids at levels comparable to those found in SpSLdes. By contrast, L. major and T. cruzi enzymes showed either no or negligible activities. Using the HPLC system coupled to electrospray tandem quadrupole/time of flight mass spectrometry we were able to detect significant levels of desaturated and hydroxylated sphingoid bases in extracts of all transformed yeast mutants, except for those transformed with the empty vector. These results indicate that S. pombe, T. brucei, T. cruzi and L. major enzymes are all bifunctional. Using the same methodology, desaturated and hydroxylated sphingoid bases were detected in T. cruzi epimastigotes and L. major promastigote cells, as described previously, and in T. brucei procyclic and bloodstream forms for the first time.

Discovery of a ß-glucosidase inhibitor from a chemically engineered extract prepared through sulfonylation.

A semisynthetic ß-glucosidase inhibitor was identified from a chemically engineered extract prepared by reaction with benzenesulfonyl chloride. The structure includes a natural histamine portion and a benzenesulfonyl portion introduced during the diversification step.

Covalent double level dynamic combinatorial libraries: selectively addressable exchange processes.

Hydrazones and disulfides have been combined in one dynamic system: hydrazones were exchanged by acid catalysis in the presence of disulfide and a thiol group without interference; neutralization of the reaction medium turns off the exchange of hydrazones and, at the same time, activates thiolate-disulfide exchange.

In vitro inhibition of 1,3-beta-glucan synthase by glycolipids from convolvulaceous species.

Sixteen convolvulaceous glycolipids selected from the tricolorin (1 - 7) and orizabin (8 - 16) series, proved to be strong in vitro inhibitors of the enzyme that catalyzes the synthesis of 1,3-beta-D-glucan, a major polymer of fungal cell-walls. Results provide an insight into function of the specific structures of these complex macrocyclic lactones as inhibitors of the 1,3-beta-D-glucan synthase and open the possibility of using these compounds as starting points for the development of antifungal agents that act by inhibiting fungal cell-wall synthesis.

Isolation of antifungal saponins from Phytolacca tetramera, an Argentinean species in critic risk.

The methanolic extract of the berries of Phytolacca tetramera, an Argentinean species submitted to a great anthropic impact, and therefore in critic risk of extinction, not previously studied, showed antifungal activity against opportunistic pathogenic fungi. Through fractionation of the extract followed by agar dilution assays, three monodesmosidic triterpenoid saponins have been isolated from the butanolic extract of P. tetramera. The structures were established as phytolaccosides: B [3-O-beta-D-xylopiranosyl-phytolaccagenin], E [3-O-beta-D-glucopyranosyl-(1-->4)-beta-D-xylopiranosyl-phytolaccagenin]. and F [3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->2)-beta-D-xylopyranosyl-phytolaccagenic acid]. The three saponins belong to the olean-type triterpenoid saponins, with 28,30 dicarboxylic groups and an olefinic double bond on C-12. Phytolaccosides B and E but not phytolaccoside F, showed antifungal activities against a panel of human pathogenic opportunistic fungi. Phytolaccoside B was the most active compound and showed the broadest spectrum of action. The most sensitive fungus was Trichophyton mentagrophytes.