Design, Synthesis and Biological Evaluation of Novel Primaquine-Cinnamic Acid Conjugates of the Amide and Acylsemicarbazide Type

Hydrazinecarboxamides: Comprehensive review of their anticancer, anticonvulsive, anti-inflammatory, enzyme inhibition, antioxidant and other activities

This review comprehensively summarizes recent advances in the field of hydrazinecarboxamide (semicarbazide) derivatives, highlighting their significant therapeutic potential and a broad spectrum of biological activities. As a promising and privileged scaffold in medicinal chemistry, hydrazinecarboxamides have emerged as a versatile class of compounds with significant bioactive properties. Based on their substitutions, their structural diversity permits extensive chemical modifications to enhance their interactions with various biological targets to combat multiple disorders. Notable, this group of compounds has shown significant efficacy against numerous cancer cell lines through diverse mechanisms of action and potent inhibition of enzymes, including cholinesterases, carbonic anhydrases, cyclooxygenases, lipoxygenases, etc. Beyond these, they have also been investigated for their anticonvulsive, analgesic/anti-inflammatory, and antioxidant properties, with detailed structure-activity relationships. For many applications, the hybridization of hydrazinecarboxamides with other bioactive scaffolds, such as primaquine, is of particular interest and offers advantages. Despite their promises, challenges such as suboptimal physicochemical properties and selectivity issues of certain derivatives require further effort. The review aims to inspire future innovation in the design and development of new potential hydrazinecarboxamide-based drugs, addressing existing challenges and expanding their therapeutic applications.

Hidden potential of hydrazinecarboxamides (semicarbazides) as potential antimicrobial agents: A review

Hydrazinecarboxamides (semicarbazides) are increasingly recognized as a versatile scaffold in developing potential antimicrobial agents. In addition to a brief overview of the synthetic methods to prepare them, this review comprehensively analyses their antimicrobial properties. These derivatives have demonstrated potent activity against a broad spectrum of mycobacteria, bacterial and fungal pathogens, highlighting their potential to address critical human health challenges, including neglected diseases, and to combat growing antimicrobial resistance. They have also been investigated for their antiviral and antiparasitic properties. The review also summarizes structure-activity relationships, known mechanisms of action and emphasizes the crucial role of the hydrazinecarboxamide moiety in facilitating interactions with biological targets. The combination of hydrazinecarboxamides with other bioactive scaffolds (primaquine, isoniazid, etc.) has led to an identification of promising drug candidates, including those active against resistant strains, offering a promising approach for future innovations in the field of antimicrobial therapy. Attention is also drawn to limitations of hydrazinecarboxamides (poor physicochemical properties, cytotoxicity to human cells, and insufficient target selectivity), which may hinder their clinical application.

Secondary Metabolites and Their Biological Evaluation from the Aerial Parts of Staehelina uniflosculosa Sibth. & Sm. (Asteraceae)

Phytochemical investigation of Staehelina uniflosculosa Sibth. & Sm. resulted in the isolation of twenty-two natural products: eleven sesquiterpene lactones, artemorin (1), tamirin (2), tanachin (3), reynosin (4), baynol C (5), desacetyl-β-cyclopyrethrosin (6), 1β-hydroxy-4α-methoxy-5α,7α,6β-eudesm-11(13)-en-6,12-olide (7), 1β,4α,6α-trihydroxyeudesm-11-en-8α,12-olide (8), 1β-hydroxy-arbusculin A (9), methyl-1β,4α,6α-trihydroxy-5α,7αH-eudesm-11(13)-en-12-oate (10) and methyl-1β,6α,8α-trihydroxy-5α,7αH-eudesma-4(15),11(13)-dien-12-oate (11); one lignan, pinoresinol (12); one norisoprenoid, loliolide (13); six flavonoids (four genins and two glycosides), hispidulin (14), nepetin (15), jaceosidin (16), eriodictyol (17), eriodictyol-3'-O-β-D-glucoside (18) and eriodictyol-7-O-β-D-glucuronide (19); and three phenolic derivatives (one phenolic acid and two phenolic glucosides), protocatechuic acid (20), arbutin (21) and nebrodenside A (22). From the isolated compounds, only nepetin (15) has been reported previously from the Staehelina genus and, to the best of our knowledge, it is the first time that compound (18) has been identified in Asteraceae. A number of these substances were tested for (a) inhibition of lipoxygenase and acetylocholinesterase, (b) their antioxidant activity using the DPPH (1,1-Diphenyl-2-picrylhydrazyl) method or/and (c) inhibition of lipid peroxidation. The tested components exhibited low antioxidant activity with the exception of 5 and 22, while the effectiveness of these compounds in the inhibition of acetylocholinesterase is limited. Furthermore, Molinspiration, an online computer tool, was used to determine the bioactivity ratings of the isolated secondary metabolites. The compounds' bioactivity ratings for potential therapeutic targets were very promising.

Synthesis of Ursolic Acid-based Hybrids: In Vitro Antibacterial, Cytotoxicity Studies, In Silico Physicochemical and Pharmacokinetic Properties

BACKGROUND

There is a critical need for the discovery of novel and effective antibacterial or anticancer molecules.

OBJECTIVES

Amine-linked ursolic acid-based hybrid compounds were prepared in good yields in the range of 60-68%.

METHODS

Their molecular structures were successfully confirmed using different spectroscopic methods including 1H/13C NMR, UHPLC-HRMS and FTIR spectroscopy. The in vitro cytotoxicity of some of these hybrid molecules against three human tumour cells, such as MDA-MB23, MCF7, and HeLa was evaluated using the MTT colorimetric method.

RESULT

Their antibacterial efficacy was evaluated against eleven bacterial pathogens using a serial dilution assay. Majority of the bacterial strains were inhibited significantly by compounds 17 and 24, with the lowest MIC values in the range of 15.3-31.25 μg/mL. Compound 16 exhibited higher cytotoxicity against HeLa cells than ursolic acid, with an IC50 value of 43.64 g/mL.

CONCLUSION

The in vitro antibacterial activity and cytotoxicity of these hybrid compounds demonstrated that ursolic acid-based hybrid molecules are promising compounds. Further research into ursolic acid-based hybrid compounds is required.

Ferulic, Sinapic, 3,4-Dimethoxycinnamic Acid and Indomethacin Derivatives with Antioxidant, Anti-Inflammatory and Hypolipidemic Functionality

A series of thiomorpholine and cinnamyl alcohol derivatives, conjugated with cinnamic acid-containing moieties, such as ferulic acid, sinapic acid and 3,4-dimethoxycinnamic acid, were synthesized and tested for their antioxidant, anti-inflammatory and hypolipidemic properties. An indomethacin ester with 2,6-di-tert-butyl-4-(hydroxymethyl)phenol was also prepared for reasons of comparison. The majority of the compounds demonstrated considerable antioxidant capacity and radical scavenging activity, reaching up to levels similar to the well-known antioxidant trolox. Some of them had an increased anti-inflammatory effect on the reduction of carrageenan-induced rat paw edema (range 17-72% at 150 μmol/kg), having comparable activity to the NSAIDs (non-steroidal anti-inflammatory drugs) used as reference. They had moderate activity in soybean lipoxygenase inhibition. All the tested compounds exhibited a significant decrease in lipidemic indices in Triton-induced hyperlipidemia in rats, whilst the most active triglycerides and total cholesterol decreased by 72.5% and 76%, respectively, at 150 μmol/kg (i.p.), slightly better than that of simvastatin, a well-known hypocholesterolemic drug, but with negligible triglyceride-lowering effect. Since our designed compounds seem to exhibit multiple pharmacological activities, they may be of use in occasions involving inflammation, oxidative stress, lipidemic deregulation and degenerative conditions.

Insights into Antimalarial Activity of N-Phenyl-Substituted Cinnamanilides

Due to the urgent need of innovation in the antimalarial therapeutic arsenal, a series of thirty-seven ring-substituted N-arylcinnamanilides prepared by microwave-assisted synthesis were subjected to primary screening against the chloroquine-sensitive strain of P. falciparum 3D7/MRA-102. The lipophilicity of all compounds was experimentally determined as the logarithm of the capacity factor k, and these data were subsequently used in the discussion of structure-activity relationships. Among the screened compounds, fourteen derivatives exhibited IC₅₀ from 0.58 to 31 µM, whereas (2E)-N-(4-bromo-2-chlorophenyl)-3-phenylprop-2-enamide (24) was the most effective agent (IC₅₀ = 0.58 µM). In addition, (2E)-N-[2,6-dibromo-4-(trifluoromethyl)- phenyl]-3-phenylprop-2-enamide (36), (2E)-N-[4-nitro-3-(trifluoromethyl)phenyl]-3-phenylprop- 2-enamide (18), (2E)-N-(2-bromo-5-fluorophenyl)-3-phenylprop-2-enamide (23), and (2E)-3-phenyl-N-(3,4,5-trichlorophenyl)prop-2-enamide (33) demonstrated efficacy in the IC₅₀ range from 2.0 to 4.3 µM, comparable to the clinically used standard chloroquine. The results of a cell viability screening performed using THP1-Blue™ NF-κB cells showed that none of these highly active compounds displayed any significant cytotoxic effect up to 20 μM, which makes them promising Plasmodium selective substances for further investigations.

Phytochemistry, biological activities and in silico molecular docking studies of Oxalis pes-caprae L. compounds against SARS-CoV-2

Phytochemicals are directly involved in therapeutic treatment or precursors to synthesize useful drugs. The current study was aimed to evaluate the phytocompounds and their biopotentials using methanolic and n-hexane extracts of various parts of Oxalis pes-caprae. For the phytochemical analysis, standard procedures were used, whereas Aluminum Chloride reagent and Follin-ciocalteau reagent methods were used to determine total flavonoid and phenolic contents. Radical scavenging DPPH, phosphomolybdenum reduction, and reducing power assays were used to assess antioxidative potentials. Antibacterial potential was determined by applying disc diffusion method while cytotoxicity was determined employing brine shrimp assay. FT-IR (Fourier-transform infrared) analysis was utilized to gather spectral information, while molecular docking tools were employed to look at how O. pes-caprae plant-based ligands interact with the target protein COVID-19 3CLPro (PDB:6LU7). Phenols, flavonoids, alkaloids and saponins were tested positive in preliminary phytochemical studies. TPC and TFC in different extracts ranging from (38.55 ± 1.72) to (65.68 ± 0.88) mg/g GAE/g and (24.75 ± 1.80) to (14.83 ± 0.92) mg/g QUE/g were used respectively. IC₅₀ value (24.75 ± 0.76 g/mL) by OXFH, total antioxidant capacity (55.89 ± 1.75) mg/g by OXLM, reducing potential (34.98 ± 1.089) mg/g by OXSM, maximum zone of inhibition against B. subtilis (24 ± 0.65 mm) by OXLM and maximum cytotoxicity 96% with LD₅₀ 19.66 (μg/mL) by OXSM were the best calculated values among all extracts. Using molecular docking, it was found that Caeruleanone A, 2',4'-Dihydroxy-2″-(1-hydroxy-1-methylethyl) dihydrofuro [2,3-h] flavanone and Vadimezan demonstrated best affinity with the investigated SARS CoV-2 Mpro protein. This work provide justification about this plant as a source of effective phytochemicals and their potential against microbes could lead to development of biosafe drugs for the welfare of human being. In future, different in vitro and in vivo biological studies can be performed to further investigate its biomedical potentials.

Natural Cinnamic Acid Derivatives: A Comprehensive Study on Structural, Anti/Pro-Oxidant, and Environmental Impacts

Cinnamic acid (CA), p-coumaric acid (4-hydroxycinnamic acid, 4-HCA), caffeic acid (3,4-vdihydroxycinnamic acid, 3,4-dHCA), and 3,4,5-trihydroxycinnamic acid (3,4,5-tHCA) were studied for their structural, anti-/pro-oxidant properties and biodegradability. The FT-IR, FT-Raman, UV/Vis, ¹H and ¹³C NMR, and quantum chemical calculations in B3LYP/6-311++G** were performed to study the effect on number and position of hydroxyl group in the ring on the molecular structure of molecules. The antioxidant properties of the derivatives were examined using DPPH^● and HO^● radicals scavenging assays, ferric ion reducing antioxidant power (FRAP), cupric reducing antioxidant capacity (CUPRAC), inhibition of linoleic acid oxidation, as well as the biological antioxidant assay with Saccharomyces cerevisiae. Moreover, the pro-oxidant activity of compounds in Trolox oxidation assay was estimated. The effect of the derivatives on environment on the basis of increasing the carbon and nitrogen compounds transformation processes occurring in biological wastewater treatment was studied.

Medicinal chemistry updates on quinoline- and endoperoxide-based hybrids with potent antimalarial activity

The resistance of conventional antimalarial drugs against the malarial parasite continues to pose a challenge to control the disease. The indiscriminate exploitation of the available antimalarials has resulted in increasing treatment failures, which urges on the search for novel lead molecules. Artemisinin-based combination therapy (ACT) is the current WHO-recommended first-line treatment for the majority of malaria cases. Hybrid molecules offer a newer strategy for the development of next-generation antimalarial drugs. These comprise molecules, each with an individual pharmacological activity, linked together into a single hybrid molecule. This approach has been utilized by several research groups to develop molecules with potent antimalarial activity. In this review, we provide an overview of the pivotal roles of quinoline- and endoperoxide-based hybrids as inhibitors of the life-cycle progression of Plasmodium. Based on the exhaustive literature reports, we have collated the structural and functional analyses of quinoline- and endoperoxide-based hybrid molecules that show potency equal to or greater than those of the individual compounds, offering an effective therapeutics option for clinical use.

Synthesis, in silico ADME, molecular docking and in vitro cytotoxicity evaluation of stilbene linked 1,2,3-triazoles

Series of (E)-1-benzyl-4-((4-styrylphenoxy)methyl)-1H-1,2,3-triazoles 7a-x were obtained by Wittig reaction between 4-((1-benzyl-1H-1,2,3-triazol-4-yl)methoxy)benzaldehydes 5a-d and benzyl triphenylphosphonium halides 6a-f in benzene. The structures of the synthesized compounds were confirmed by FTIR, NMR (1H and 13C NMR) spectroscopy, and mass spectrometry. All synthesized compounds were screened for their cytotoxic activity against human cancer cell lines including pancreatic carcinoma, colorectal carcinoma, lung carcinoma, and leukemias such as acute lymphoblastic, chronic myeloid, and non-Hodgkinson lymphoma cell lines. In vitro cytotoxicity data showed that compounds 7c, 7e, 7h, 7j, 7k, 7r, and 7w were moderately cytotoxic (11.6-19.3 μM) against the selected cancer cell lines. These cytotoxicity findings were supported using molecular docking studies of the compounds against 1TUB receptor. The drug-likeness properties of the compounds evaluated by in silico ADME analyses. Resveratrol linked 1,2,3-triazoles were more sensitive towards human carcinoma cell lines but least sensitive towards leukemia and lymphoma cell lines.

Itaconic acid hybrids as potential anticancer agents

Abstract

In this paper, we report the synthesis of novel hybrids 2–14 based on itaconic acid and fluoroaniline, pyridine, indole and quinoline scaffolds. Itaconic acid is a naturally occurring compound with a Michael acceptor moiety, a key structural feature in several anticancer and antiviral drugs, responsible for the covalent binding of a drug to the cysteine residue of a specific protein. Aromatic parts of the hybrids also come from the substances reported as anticancer or antiviral agents. The synthetic route employed to access the amido-ester hybrids 2–13 used monomethyl itaconate or monomethyl itaconyl chloride and corresponding amines as the starting materials. Dimers 14 and 15 with two aminoindole or mefloquine moieties were prepared from itaconic acid and corresponding amino derivative, using standard coupling conditions (HATU/DIEA). All hybrids exerted anticancer effects in vitro against almost all the tumour cell lines that were evaluated (MCF-7, HCT 116, H460, LN-229, Capan-1, DND-41, HL-60, K-562, Z-138). Solid tumour cells were, in general, more responsive than the haematological cancer cells. The MCF-7 breast adenocarcinoma cell line appeared the most sensitive. Amido-ester 12 with chloroquine core and mefloquine homodimer 15 showed the highest activity with GI₅₀ values between 0.7 and 8.6 µM. In addition, compound 15 also exerted antiviral activity against Zika virus and Coxsackievirus B4 in low micromolar concentrations.

Graphic abstract

Electronic supplementary material

The online version of this article (10.1007/s11030-020-10147-6) contains supplementary material, which is available to authorized users.

Cinnamic Acid Conjugates in the Rescuing and Repurposing of Classical Antimalarial Drugs

Cinnamic acids are compounds of natural origin that can be found in many different parts of a wide panoply of plants, where they play the most diverse biological roles, often in a conjugated form. For a long time, this has been driving Medicinal Chemists towards the investigation of the therapeutic potential of natural, semi-synthetic, or fully synthetic cinnamic acid conjugates. These efforts have been steadily disclosing promising drug leads, but a wide chemical space remains that deserves to be further explored. Amongst different reported approaches, the combination or conjugation of cinnamic acids with known drugs has been addressed in an attempt to produce either synergistic or multi-target action. In this connection, the present review will focus on efforts of the past decade regarding conjugation with cinnamic acids as a tool for the rescuing or the repurposing of classical antimalarial drugs, and also on future perspectives in this particular field of research.

Drug Repurposing in the Development of Anticancer Agents

BACKGROUND

Research into repositioning known drugs to treat cancer other than the originally intended disease continues to grow and develop, encouraged in part, by several recent success stories. Many of the studies in this article are geared towards repurposing generic drugs because additional clinical trials are relatively easy to perform and the drug safety profiles have previously been established.

OBJECTIVE

This review provides an overview of anticancer drug development strategies which is one of the important areas of drug restructuring.

METHODS

Repurposed drugs for cancer treatments are classified by their pharmacological effects. The successes and failures of important repurposed drugs as anticancer agents are evaluated in this review.

RESULTS AND CONCLUSION

Drugs could have many off-target effects, and can be intelligently repurposed if the off-target effects can be employed for therapeutic purposes. In cancer, due to the heterogeneity of the disease, often targets are quite diverse, hence a number of already known drugs that interfere with these targets could be deployed or repurposed with appropriate research and development.

Antiproliferative evaluation of various aminoquinoline derivatives

Four classes of aminoquinoline derivatives were prepared: primaquine ureas 1a-f, primaquine bis-ureas 2a-f, chloroquine fumardiamides 3a-f and mefloquine fumardiamides 4a-f. Their antiproliferative activities against breast adeno-carcinoma (MCF-7), lung carcinoma (H460) and colon carcinoma (HCT 116 and SW620) cell lines were evaluated in vitro, using MTT cell proliferation assay. The results revealed a low activity of primaquine urea and bis-urea derivatives and high activity of all fumardiamides, with IC50 values in low micromolar range against all tested cancer cell lines.

Primaquine derivatives: Modifications of the terminal amino group

Numerous modifications of the well-known antimalarial drug primaquine, both at the quinoline ring and at the primary amino group, have been reported, mostly to obtain antimalarial agents with improved bioavailability, reduced toxicity and/or prolonged activity. Modifications of the terminal amino group were made with the main idea to prevent the metabolic pathway leading to inactive and toxic carboxyprimaquine (follow-on strategy), but also to get compounds with different activity (repurposing strategy). The modifications undertaken until 2009 were included in a review published in the same year. The present review covers various classes of primaquine N-derivatives with diverse biological profiles, prepared in the last decade by our research group as well as the others. We have summarized the synthetic procedures applied for their preparation and discussed the main biological results. Several hits for the development of novel antiplasmodial, anticancer, antimycobacterial and antibiofilm agents were identified.

Primaquine and Chloroquine Fumardiamides as Promising Antiplasmodial Agents

This paper describes a continuation of our efforts in the pursuit of novel antiplasmodial agents with optimized properties. Following our previous discovery of biologically potent asymmetric primaquine (PQ) and halogenaniline fumardiamides (1-6), we now report their significant in vitro activity against the hepatic stages of Plasmodium parasites. Furthermore, we successfully prepared chloroquine (CQ) analogue derivatives (11-16) and evaluated their activity against both the hepatic and erythrocytic stages of Plasmodium. Our results have shown that PQ fumardiamides (1-6) exert both higher activity against P. berghei hepatic stages and lower toxicity against human hepatoma cells than the parent drug and CQ derivatives (11-16). The favourable cytotoxicity profile of the most active compounds, 5 and 6, was corroborated by assays performed on human cells (human breast adenocarcinoma (MCF-7) and non-tumour embryonic kidney cells (HEK293T)), even when glucose-6-phosphate dehydrogenase (G6PD) was inhibited. The activity of CQ fumardiamides on P. falciparum erythrocytic stages was higher than that of PQ derivatives, comparable to CQ against CQ-resistant strain PfDd2, but lower than CQ when tested on the CQ-sensitive strain Pf3D7. In addition, both sets of compounds showed favourable drug-like properties. Hence, quinoline fumardiamides could serve as a starting point towards the development of safer and more effective antiplasmodial agents.

Synthesis and antiplasmodial evaluation of novel mefloquine-based fumardiamides

The paper is focused on the synthesis and screening of the antiplasmodial activity of novel fumardiamides 5-10 with the mefloquine pharmacophore and a Michael acceptor motif. Multi-step reactions leading to the title compounds included two amide bond formations. The first amide bond was achieved by the reaction of (E)-ethyl 4-chloro-4-oxobut-2-enoate (1) and N1-(2,8-bis(trifluoromethyl)quinolin-4-yl) butane-1,4-diamine (2). The obtained ester 3 was hydrolyzed and gave acid 4, which then reacted with the selected halogenanilines in the presence of HATU/DIEA and formed products 5-10. Title compounds showed marked, dose dependent activity in vitro against hepatic stages of Plasmodium berghei. IC50 values of the most active compounds 5, 7 and 9 bearing 3-fluoro, 3-chloro and 3-trifluoromethyl substituents were 3.04-4.16 µmol L-1, respectively. On the other hand, the compounds exerted only weak activity against the erythrocytic stages of two P. falciparum strains (Pf3D7 and PfDd2) in vitro, with the exception of compound 5 (IC50 = 2.9 µmol L-1).

Second generation of primaquine ureas and bis-ureas as potential antimycobacterial agents

Here, we describe design and synthesis of twelve novel compounds bearing primaquine motif and hydroxy- or halogenamine linked by an urea or bis-urea spacer. Preparation of ureas 3a-f started with the conversion of primaquine to benzotriazolide 2 and aminolysis of the later compound by 4-(2-aminoethyl)phenol or amino alcohols bearing fluorine atom, cycloalkyl or trifluoromethyl group under microwave irradiation. The four-step sequence leading to bis-ureas 6a-f included preparation of benzotriazolide 2 and two intermediates, semicarbazide 4 and benzotriazole bis-urea 5, which upon aminolysis with the same aminophenol or amino alcohols gave the title compounds. Antimycobacterial screening detected three active compounds against Mycobacterium marinum and M. tuberculosis, namely 3b, 3f and 6f, derived from cyclobutyl amino alcohol or amino phenol.

Insights into biological activity of ureidoamides with primaquine and amino acid moieties

Primaquine (PQ) ureidoamides 5a-f were screened for antimicrobial, biofilm eradication and antioxidative activities. Susceptibility of the tested microbial species towards tested compounds showed species- and compound-dependent activity. N-(diphenylmethyl)-2-[({4-[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)amino]-4-methylpentanamide (5a) and 2-(4-chlorophenyl)-N-(diphenylmethyl)-2-[({4-[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)amino]acetamide (5d) showed antibacterial activity against S. aureus strains (MIC = 6.5 µg/ml). Further, compounds 5c and 5d had weak antibacterial activity against Escherichia coli and Pseudomonas aeruginosa. None of the tested compounds showed a wide spectrum of antifungal activity. In contrast, most of the compounds exerted strong activity in a biofilm eradication assay against E. coli, P. aeruginosa and Candida albicans, comparable to or even higher than gentamycin, amphotericin B or parent PQ. The most active compounds were 5a and 5b. Tested compounds were inactive against biofilm formation by C. parapsylosis, Enterococcus faecalis, C. tropicalis and C. krusei. Compounds 5b-f significantly inhibited lipid peroxidation (80-99%), whereas compound 5c presented interesting LOX inhibition.

Insights into the mechanism of antiproliferative effects of primaquine-cinnamic acid conjugates on MCF-7 cells

In our previous paper, we showed that three primaquine-cinnamic acid conjugates composed of primaquine (PQ) residue and cinnamic acid derivatives (CADs) bound directly by an amide linkage (1) or through an acylsemicarbazide spacer (2 and 3) had significant growth inhibitory effects on some cancer cell lines. Compound 1 induced significant growth inhibition in the colorectal adenocarcinoma (SW620), human breast adenocarcinoma (MCF-7) and cervical carcinoma (HeLa) cell lines, while compounds 2 and 3 selectively inhibited the growth of MCF-7 cells. To better understand the underlying mechanisms of action of these PQ-CADs, morphological studies of the effects of test compounds on MCF-7 cells were undertaken using haematoxylin and eosin stain. Further analysis to determine the effects of test compounds on caspase activity and on the levels of apoptosis proteins were undertaken using the enzyme-linked immunosorbent assay (ELISA). Haematoxylin and eosin staining revealed that compounds 1 and 3 induced morphological changes in MCF-7 cells characteristic of apoptosis, while 2-treated cells were in interphase. Cell cycle analysis showed that cells treated with 1 and 3 were in sub-G1, while cells treated with 2 were mainly in interphase (G1 phase). Further, the study showed that the treatment of MCF-7 cells with 1 and 3 resulted in poly ADP ribose polymerase (PARP) cleavage as well as caspase-9 activation, indicating that they induced apoptotic cell death. We further investigated their effects on two important processes during metastasis, namely, migration and invasion. Compounds 1 and 3 inhibited the migration and invasion of MCF-7 cells, while compound 2 had a marginal effect.

SAHAquines, Novel Hybrids Based on SAHA and Primaquine Motifs, as Potential Cytostatic and Antiplasmodial Agents

We report the synthesis of SAHAquines and related primaquine (PQ) derivatives. SAHAquines are novel hybrid compounds that combine moieties of suberoylanilide hydroxamic acid (SAHA), an anticancer agent with weak antiplasmodial activity, and PQ, an antimalarial drug with low antiproliferative activity. The preparation of SAHAquines is simple, cheap, and high yielding. It includes the following steps: coupling reaction between primaquine and a dicarboxylic acid monoester, hydrolysis, a new coupling reaction with O-protected hydroxylamine, and deprotection. SAHAquines 5 a-d showed significant reduction in cell viability. Among the three human cancer cell lines (U2OS, HepG2, and MCF-7), the most responsive were the MCF-7 cells. The antibodies against acetylated histone H3K9/H3K14 in MCF-7 cells revealed a significant enhancement following treatment with N-hydroxy-N'-{4-[(6-methoxyquinolin-8-yl)amino]pentyl}pentanediamide (5 b). Ethyl (2E)-3-({4-[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)prop-2-enoate (2 b) and SAHAquines were the most active compounds against both the hepatic and erythrocytic stages of Plasmodium parasites, some of them at sub-micromolar concentrations. The results of our research suggest that SAHAquines are promising leads for new anticancer and antimalarial agents.

Asymmetric Primaquine and Halogenaniline Fumardiamides as Novel Biologically Active Michael Acceptors

Novel primaquine (PQ) and halogenaniline asymmetric fumardiamides 4a⁻f, potential Michael acceptors, and their reduced analogues succindiamides 5a⁻f were prepared by simple three-step reactions: coupling reaction between PQ and mono-ethyl fumarate (1a) or mono-methyl succinate (1b), hydrolysis of PQ-dicarboxylic acid mono-ester conjugates 2a,b to corresponding acids 3a,b, and a coupling reaction with halogenanilines. 1-[bis(Dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU) was used as a coupling reagent along with Hünig's base. Compounds 4 and 5 were evaluated against a panel of bacteria, several Mycobacterium strains, fungi, a set of viruses, and nine different human tumor cell lines. p-Chlorofumardiamide 4d showed significant activity against Staphylococcus aureus,Streptococcus pneumoniae and Acinetobacter baumannii, but also against Candida albicans (minimum inhibitory concentration (MIC) 6.1⁻12.5 µg/mL). Together with p-fluoro and p-CF₃ fumardiamides 4b,f, compound 4d showed activity against Mycobacterium marinum and 4b,f against M. tuberculosis. In biofilm eradication assay, most of the bacteria, particularly S. aureus, showed susceptibility to fumardiamides. m-CF₃ and m-chloroaniline fumardiamides 4e and 4c showed significant antiviral activity against reovirus-1, sindbis virus and Punta Toro virus (EC50 = 3.1⁻5.5 µM), while 4e was active against coxsackie virus B4 (EC50 = 3.1 µM). m-Fluoro derivative 4a exerted significant cytostatic activity (IC50 = 5.7⁻31.2 μM). Acute lymphoblastic leukemia cells were highly susceptible towards m-substituted derivatives 4a,c,e (IC50 = 6.7⁻8.9 μM). Biological evaluations revealed that fumardiamides 4 were more active than succindiamides 5 indicating importance of Michael conjugated system.

Primaquine hybrids as promising antimycobacterial and antimalarial agents

Four series of primaquine (PQ) derivatives were screened for antitubercular and antiplasmodial activity: amides 1a-k, ureas 2a-s, semicarbazides 3a-c and bis-ureas 4a-u. Antimycobacterial activity of PQ derivatives against Mycobacterium tuberculosis (MTB), M. avium complex (MAC) and M. avium subsp. paratuberculosis (MAP) were evaluated in vitro and compared with PQ and the standard antitubercular drugs. In general, the PQ derivatives showed higher potency than the parent compound. Most of the compounds of series 1 and 2 showed high activity against MAP, comparable or even higher than the relevant drug ciprofloxacin, and weak or no activity against MTB and MAC. bis-Trifluoromethylated cinnamamide 1k showed low cytotoxicity and high activity against all three Mycobacterium species and their activities were comparable or slightly higher than those of the reference drugs. PQ urea derivatives with hydroxyl, halogen and trifluoromethyl substituents on benzene ring 2f-p exerted very strong antimycobacterial activity towards all tested mycobacteria, stronger than PQ and the relevant standard drug(s). Unfortunately, these compounds had relatively high cytotoxicity, except bromo 2l and trifluoromethyl 2m, 2n derivatives. In general, meta-substituted derivatives were more active than analogues para-derivatives. Phenyl ureas were also more active than cycloalkyl or hydroxyalkyl ureas. Semicarbazide 3a showed similar activity as PQ, while the other two semicarbazides were inactive. Bis-urea derivatives 4 were generally less active than the urea derivatives sharing the same scaffold, differing only in the spacer type. Out of 21 evaluated bis-urea derivatives, only p-Cl/m-CF₃ phenyl derivative 4p, benzhydryl derivatives 4t and 4u and bis-PQ derivative 4s showed high activity, higher than all three reference drugs. After comparison of activity and cytotoxicity, urea 2m and bis-urea 4u could be considered as the most promising agents. Antimalarial potential of PQ derivatives in vitro against the liver stage of P. berghei was evaluated as well. 3-(4-Chlorophenyl)-1-[({4-[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)amino]urea (4l) was the most active compound (IC₅₀ = 42 nM; cytotoxicity/activity ratio >2000). Our results bring new insights into development of novel anti-TB and antimalarial compounds.