Bianca Pérez

N‑Cinnamoylated Chloroquine Analogues as Dual-Stage Antimalarial Leads

The control of malaria is challenged by drug resistance, and new antimalarial drugs are needed. New drug discovery efforts include consideration of hybrid compounds as potential multitarget antimalarials. Previous work from our group has demonstrated that hybrid structures resulting from cinnamic acid conjugation with heterocyclic moieties from well-known antimalarials present improved antimalarial activity. Now, we report the synthesis and SAR analysis of an expanded series of cinnamic acid derivatives displaying remarkably high activities against both blood- and liver-stage malaria parasites. Two compounds judged most promising, based on their in vitro activity and druglikeness according to the Lipinski rules and Veber filter, were active in vivo against blood-stage rodent malaria parasites. Therefore, the compounds reported represent a new entry as promising dual-stage antimalarial leads.

Novel cinnamic acid/4-aminoquinoline conjugates bearing non-proteinogenic amino acids: Towards the development of potential dual action antimalarials

A series of cinnamic acid/4-aminoquinoline conjugates conceived to link, through a proper retro-enantio dipeptide, a heterocyclic core known to prevent hemozoin formation, to a trans-cinnamic acid motif capable of inhibiting enzyme catalytic Cys residues, were synthesized as potential dual-action antimalarials. The effect of amino acid configuration and the absence of the dipeptide spacer were also assessed. The replacement of the D-amino acids by their natural L counterparts led to a decrease in both anti-plasmodial and falcipain-inhibitory activity, suggesting that the former are preferable. Molecules with such spacer were active against blood-stage Plasmodium falciparum, in vitro, and hemozoin formation, implying that the dipeptide has a key role in mediating these two activities. In turn, compounds without spacer were better falcipain-2 inhibitors, likely because these compounds are smaller and have their vinyl bonds in closer vicinity to the catalytic Cys, as suggested by molecular modeling calculations. These novel conjugates constitute promising leads for the development of new antiplasmodials targeted at blood-stage malaria parasites.

Cinnamic Acid/Chloroquinoline Conjugates as Potent Agents against Chloroquine‐Resistant Plasmodium falciparum

Cinnamic acid derivatives containing a 4-amino-7-chloroquinoline scaffold (blue) and substituted cinnamoyl building blocks (green) linked through an alkylamine chain (red) were found to have potent (11-59 nM) in vitro activities against erythrocytic chloroquine- resistant Plasmodium falciparum.

In vitro efficiency of 9-(N-cinnamoylbutyl)aminoacridines against blood- and liver-stage malaria parasites

Novel 9-aminoacridine derivatives were synthesized by linking the heteroaromatic core to different cinnamic acids through an aminobutyl chain. The test compounds demonstrated mid-nanomolar in vitro activity against erythrocytic stages of the chloroquine-resistant W2 strain of the human malaria parasite Plasmodium falciparum. Two of the most active derivatives also showed in vitro activity against liver-stage Plasmodium berghei, with activity greater than that of the reference liver-stage antimalarial primaquine. The compounds were not toxic to human hepatoma cells at concentrations up to 5 μM. Hence, 9-(N-cinnamoylbutyl)aminoacridines are a new class of leads for prevention and treatment of malaria.

Development of Plasmodium falciparum Protease Inhibitors in the Past Decade (2002-2012)

New drug targets for the development of antimalarial drugs have emerged after the unveiling of the Plasmodium falciparum genome in 2002. Potential antimalarial drug targets can be broadly classified into three categories according to their function in the parasites life cycle: (i) biosynthesis, (ii) membrane transport and signaling, and (iii) hemoglobin catabolism. The latter plays a key role, as inhibition of hemoglobin degradation impairs maturation of bloodstage malaria parasites, ultimately leading to remission or even cure of the most severe stage of the infection. Intraerythrocytic Plasmodia parasites have limited capacity to biosynthesize amino acids which are vital for their growth. Therefore, the parasites obtain those essential amino acids via degradation of host cell hemoglobin, making this a crucial process for parasite survival. Several plasmodial proteases are involved in hemoglobin catabolism, among which plasmepsins and falcipains are well-known examples. Hence, development of P. falciparum protease inhibitors is a promising approach to antimalarial chemotherapy, as highlighted by the present review which is focused on the Medicinal Chemistry research effort recorded in the past decade in this particular field.

Biocatalytic synthesis of ultra-long-chain fatty acid sugar alcohol monoesters

An array of ultra-long-chain fatty acid sugar alcohol monoesters, with behenic acid as an acyl representative and sugar alcohols altered from ethylene glycol to glycerol, erythritol, pentaerythritol, arabitol, xylitol and sorbitol, were enzymatically synthesized in high purity and selectivity. The molecular structures of the synthetic compounds were confirmed by 1H NMR, FT-IR and MS analysis, and the thermal properties were primarily characterized by DSC analysis. The molecular packing and thermal properties of synthetic sugar alcohol monobehenates (SAMBs) were investigated by Temp-Ramp-FT-IR. For in vivo application purposes, the enzymatic lipolysis of synthesized SAMBs was examined by a PPL (porcine pancreatic lipase)-mediated in vitro digestion test, and improved resistance of most SAMBs to enzymatic lipolysis, in comparison to glycerol monopalmitate, was observed. FT-IR spectroscopic analysis of the thermotropic phase transitions of the synthetic SAMBs indicated that the thermal collapse temperatures do not vary significantly as the polar head alters, suggesting their thermostabilities are largely governed by hydrophobic interactions among the alkanyl chains, while the size, properties and volume of the polar heads may determine the packing patterns. Systemic mapping of the structure–property–function relationship of SAMBs revealed the potential of these compounds for multipurpose applications. Ethylene glycol and glycerol monobehenates enable orthorhombic packing, and could find applications in cosmetic formulation, whereas sorbitol monobehenate is capable of forming stable surfactant-free nanoparticles, which could be excellent excipients for solid lipid nanoparticles for use as delivery cargo for drugs and food ingredients.

N-Cinnamoylation of Antimalarial Classics: Quinacrine Analogues with Decreased Toxicity and Dual-Stage Activity

Plasmodium falciparum, the causative agent of the most lethal form of malaria, is becoming increasingly resistant to most available drugs. A convenient approach to combat parasite resistance is the development of analogues of classical antimalarial agents, appropriately modified in order to restore their relevance in antimalarial chemotherapy. Following this line of thought, the design, synthesis and in vitro evaluation of N‐cinnamoylated quinacrine surrogates, 9‐(N‐cinnamoylaminobutyl)‐amino‐6‐chloro‐2‐methoxyacridines, is reported. The compounds were found to be highly potent against both blood‐stage P. falciparum, chloroquine‐sensitive 3D7 (IC50=17.0–39.0 nM) and chloroquine‐resistant W2 and Dd2 strains (IC50=3.2–41.2 and 27.1–131.0 nM, respectively), and liver‐stage P. berghei (IC50=1.6–4.9 μM) parasites. These findings bring new hope for the possible future “rise of a fallen angel” in antimalarial chemotherapy, with a potential resurgence of quinacrine‐related compounds as dual‐stage antimalarial leads.

Mining catalytic promiscuity from Thermophilic archaea: an acyl-peptide releasing enzyme from Sulfolobus tokodaii (ST0779) for nitroaldol reactions

This work demonstrates that the thermophiles can be a rich source to mine catalytic promiscuity, whereby an acyl-peptide releasing enzyme from Sulfolobus tokodaii (ST0779) is identified to be a promising biocatalyst to mediate the Henry (nitroaldol) reaction. Compared to Porcine Pancreatic Lipase (PPL), ST0779 displayed superior catalytic efficiency kcat/Km (6–8 fold higher) and enantioselectivity ee% (90–99%). The catalytic versatility of ST0779 was validated as the enzyme displayed activity towards a broad scope of substituted benzaldehydes, and the electron effects of the benzaldehyde substituents were analyzed by Hammett plotting. Accordingly, this work not only presents a novel enzyme capable of catalyzing the Henry reaction with higher yield and enantioselectivity than ever reported, but also demonstrates the huge potential of Thermophilic archaea to be an optimal source for mining novel enzymes for biocatalytic promiscuity, which could provide a variety of potent biosynthesis tools to yield diverse kinds of molecules.

Recycling antimalarial leads for cancer: Antiproliferative properties of N-cinnamoyl chloroquine analogues

Cinnamic acids and quinolines are known as useful scaffolds in the discovery of antitumor agents. Therefore, N-cinnamoylated analogues of chloroquine, recently reported as potent dual-action antimalarials, were evaluated against three different cancer cell lines: MKN-28, Caco-2, and MCF-7. All compounds display anti-proliferative activity in the micromolar range against the three cell lines tested, and most of them were more active than their parent drug, chloroquine, against all cell lines tested. Hence, N-cinnamoyl-chloroquine analogues are a good start towards development of affordable antitumor leads.

Adding functionality to milk-based protein: Preparation, and physico-chemical characterization of β-lactoglobulin-phenolic conjugates

Multi-functional phenolic emulsifiers were prepared by covalently coupling β-Lactoglobulin (βLg) to caffeic acid (CA) using crosslinker chemistry at different pH conditions (pH 2.5, 6.0, and 8.5). The resulting bioconjugates were characterized by MALDI-TOF MS, differential scanning calorimetry (DSC), fluorescence-quenching, infrared and circular dichroism spectroscopies. Furthermore, the emulsifying and antioxidant properties of βLg-CA conjugates were evaluated and compared to native β-Lactoglobulin and the non-covalent β-lactoglobulin/caffeic complex (βLg/CA). Results showed: 1) An optimal molar ratio (8:1) of caffeic acid to βLg was obtained at pH 6; 2) DPPH activity of βLg-CA increases as the number of CA units coupled increases; 3) βLg-CA conjugates displayed comparable or superior water solubility than native βLg and βLg/CA. Moreover, DSC results showed that coupling of CA with βLg significantly increased the thermal stability of βLg. In summary, βLg-CA conjugates can act as effective antioxidant emulsifiers and stabilizers and may find application in food and cosmetic industries.