Anti-Trypanosomal and Antimalarial Properties of Tetralone Derivatives and Structurally Related Benzocycloalkanones

Novel quinoline derivatives with broad-spectrum antiprotozoal activities

Several quinoline derivatives incorporating arylnitro and aminochalcone moieties were synthesized and evaluated in vitro against a broad panel of trypanosomatid protozoan parasites responsible for sleeping sickness (Trypanosoma brucei rhodesiense), nagana (Trypanosoma brucei brucei), Chagas disease (Trypanosoma cruzi), and leishmaniasis (Leishmania infantum). Several of the compounds demonstrated significant antiprotozoal activity. Specifically, compounds 2c, 2d, and 4i displayed submicromolar activity against T. b. rhodesiense with half-maximal effective concentration (EC50) values of 0.68, 0.8, and 0.19 µM, respectively, and with a high selectivity relative to human lung fibroblasts and mouse primary macrophages (∼100-fold). Compounds 2d and 4i also showed considerable activity against T. b. brucei with EC50 values of 1.4 and 0.4 µM, respectively.

2-Aroyl quinazolinone: Synthesis and in vitro anti-parasitic activity

Trypanosomes and Leishmania are parasitic protozoans that affect millions of people globally. Herein we report the synthesis of 2-aroyl quinazolinones and their antiprotozoal efficacy against Trypanosoma brucei, Trypanosoma brucei rhodesiense, Trypanosoma cruzi, and Leishmania infantum. These compounds were counter-screened against a human cell line for cytotoxicity. Thirteen of the twenty target compounds in this study inhibited the growth of these parasites, with compounds KJ1, and KJ10 exhibiting IC50 values of 4.7 μM (T. b. brucei) and 1.1 μM (T. b. rhodesiense), respectively.

Synthesis of Benzocycloalkanone-Based Michael Acceptors and Biological Activities as Antimalarial and Antitrypanosomal Agents

A series of benzocycloalkanone derivatives have been prepared and evaluated as antimalarial and antitrypanosomal agents. The compounds were obtained by direct coupling of preformed 4-substituted benzaldehyde and indanone or tetralone substitutes through aldol condensation of Claisen-Schmidt using sodium hydroxide as a catalyst in ethanol at room temperature. Although designed to inhibit the formation of β-hematin in vitro, only three compounds, 10, 11, and 12, showed activities greater than 50% (75.16%, 63.02%, and 56.17%, respectively). The results of the in vivo antimalarial evaluation show that 10, 11, and 12 reduced parasitemia marginally, and an insignificant increase in the days of survival of the mice was observed. As trypanocidals, all compounds showed marginal activity as inhibitors of the proliferation of T. cruzi epimastigotes, except compound 33, with an activity of 51.08 ± 3.4% compared to the activity shown by the reference compound benznidazole 59.99 ± 2.9%. The compounds appear to have little cytotoxic effect against VERO cells in vitro; this new class of Michael acceptor agents clearly warrants further investigation.

Synthesis and in vitro antiprotozoal evaluation of novel metronidazole-Schiff base hybrids

Herein we report the synthesis of 21 novel small molecules inspired by metronidazole and Schiff base compounds. The compounds were evaluated against Trichomonas vaginalis and cross-screened against other pathogenic protozoans of clinical relevance. Most of these compounds were potent against T. vaginalis, exhibiting IC₅₀ values < 5 µM. Compound 20, the most active compound against T. vaginalis, exhibited an IC₅₀ value of 3.4 µM. A few compounds also exhibited activity against Plasmodium falciparum and Trypanosomal brucei brucei, with compound 6 exhibiting an IC₅₀ value of 0.7 µM against P. falciparum and compound 22 exhibiting an IC₅₀ value of 1.4 µM against T.b. brucei. Compound 22 is a broad-spectrum antiprotozoal agent, showing activities against all three pathogenic protozoans under investigation.

Research progress in pharmacological activities and structure-activity relationships of tetralone scaffolds as pharmacophore and fluorescent skeleton

The tetralone and tetralone derivatives, as crucial structural scaffolds of potential novel drugs targeted at multiple biological end-points, are normally found in several natural compounds and also, it can be used as parental scaffold and/or intermediate for the synthesis of a series of pharmacologically active compounds with a broad-spectrum of bioactivities including antibacterial, antitumor, CNS effect and so on. Meanwhile, SAR information of its analogues has drawn attentions among medicinal chemists, which could contribute to the further research related to tetralone derivatives aimed at multiple targets. This review encompasses pharmacological activities, SAR analysis and docking study of tetralone and its derivatives, expecting to provide a general retrospect and prospect on tetralone derivatives.

Synthesis and in vitro antitrypanosomal evaluation of novel 6-heteroarylidene-substituted quinolone derivatives

Human African trypanosomiasis is a vector-borne tropical disease of African origin. Presently, due to human migration and climate change, the disease might present global health and economic burdens as current chemotherapy of trypanosomiasis remains a challenge due to limited existing drugs, which are of poor efficacy, cause severe adverse events and are very costly. Recently, Beteck and co-workers identified a small library of 1,3,6-substituted non-fluoroquinolones that showed moderate to weak trypanocidal activity without cytotoxic effects. The current study further explored SARs of the quinolone scaffold in search for more potent trypanocidal agents. Fifteen novel quinolone derivatives bearing a heteroarylidene moiety at positon-6 and varied chemical entities at positions -1 and -3 of the quinolone scaffold were synthesized and evaluated in vitro for antitrypanosomal activity. The compounds exhibit exceptionally good antitrypanosomal activity with IC₅₀ values in the low-micromolar to sub-micromolar range (0.08-15.26 μM), with compound 6d being the most active having an IC₅₀ value of 80 nM against T.b. brucei. Compounds in this study generally have molecular weight less than 600Da, ClogP value of 2-4 and a BBB score of 1-5, hence they could be potentially effective against both stages of trypanosomiasis.

In-vitro Anti-trypanosomal and Cytotoxicity Evaluation of 3-methyl-3,4-dihydroquinazolin-2(1H)-one Derivatives

Sleeping sickness, caused by trypanosomes, is a debilitating, neglected tropical disease wherein current treatments suffer from several drawbacks such as toxicity, low activity, and poor pharmacokinetic properties, and hence the need for alternative treatment is apparent. To this effect, we screened in vitro a library of 2-quinazolinone derivatives for antitrypanosomal activity against T.b. brucei and cytotoxicity against HeLa cells. Seven compounds having no overt cytotoxicity against HeLa cells exhibited antitrypanosomal activity in the range of 0.093-45 µM were identified. The activity data suggests that the antitrypanosomal activity of this compound class is amenable to substituents at N1 and C6 positions. Compound 14: having a molecular weight of 238Da, ClogP value of 1 and a total polar surface area of 49 was identified as the most active, exhibiting an IC₅₀ value of 0.093 µM Graphical Abstract.

The in Vitro Antiplasmodial and Antiproliferative Activity of New Ferrocene-Based α-Aminocresols Targeting Hemozoin Inhibition and DNA Interaction

The conjugation of organometallic complexes to known bioactive organic frameworks is a proven strategy revered for devising new drug molecules with novel modes of action. This approach holds great promise for the generation of potent drug leads in the quest for therapeutic chemotypes with the potential to overcome the development of clinical resistance. Herein, we present the in vitro antiplasmodial and antiproliferative investigation of ferrocenyl α-aminocresol conjugates assembled by amalgamation of the organometallic ferrocene unit and an α-aminocresol scaffold possessing antimalarial activity. The compounds pursued in the study exhibited higher toxicity towards the chemosensitive (3D7) and -resistant (Dd2) strains of the Plasmodium falciparum parasite than to the human HCC70 triple-negative breast cancer cell line. Indication of cross-resistance was absent for the compounds evaluated against the multi-resistant Dd2 strain. Structure-activity analysis revealed that the phenolic hydroxy group and rotatable σ bond between the α-carbon and NH group of the α-amino-o-cresol skeleton are crucial for the biological activity of the compounds. Spectrophotometric techniques and in silico docking simulations performed on selected derivatives suggest that the compounds show a dual mode of action involving hemozoin inhibition and DNA interaction via minor-groove binding. Lastly, compound 9 a, identified as a possible lead, exhibited preferential binding for the plasmodial DNA isolated from 3D7 P. falciparum trophozoites over the mammalian calf thymus DNA, thereby substantiating the enhanced antiplasmodial activity of the compounds. The presented research demonstrates the strategy of incorporating organometallic complexes into known biologically active organic scaffolds as a viable avenue to fashion novel multimodal compounds with potential to counter the development drug resistance.

Synthesis, Structure and In Vitro Anti-Trypanosomal Activity of Non-Toxic Arylpyrrole-Based Chalcone Derivatives

With an intention of identifying chalcone derivatives exhibiting anti-protozoal activity, a cohort of relatively unexplored arylpyrrole-based chalcone derivatives were synthesized in moderate to good yields. The resultant compounds were evaluated in vitro for their potential activity against a cultured Trypanosoma brucei brucei 427 strain. Several compounds displayed mostly modest in vitro anti-trypanosomal activity with compounds 10e and 10h emerging as active candidates with IC50 values of 4.09 and 5.11 µM, respectively. More importantly, a concomitant assessment of their activity against a human cervix adenocarcinoma (HeLa) cell line revealed that these compounds are non-toxic.

Repurposing a polymer precursor: Synthesis and in vitro medicinal potential of ferrocenyl 1,3-benzoxazine derivatives

Cancer and malaria remain relevant pathologies in modern medicinal chemistry endeavours. This is compounded by the threat of development of resistance to existing clinical drugs in use as first-line option for treatment of these diseases. To counter this threat, strategies such as drug repurposing and hybridization are constantly adapted in contemporary drug discovery for the expansion of the drug arsenal and generation of novel chemotypes with potential to avert or delay resistance. In the present study, a polymer precursor scaffold, 1,3-benzoxazine, has been repurposed by incorporation of an organometallic ferrocene unit to produce a novel class of compounds showing in vitro biological activity against breast cancer, malaria and trypanosomiasis. The resultant ferrocenyl 1,3-benzoxazine compounds displayed high potency and selectivity against the investigated diseases, with IC₅₀ values in the low and sub-micromolar range against both chloroquine-sensitive (3D7) and resistant (Dd2) strains of the Plasmodium falciparum parasite. On the other hand, antitrypanosomal (Trypanosoma brucei brucei) potencies were observed between 0.15 and 38.6 μM. The majority of the compounds were not active against breast cancer cells (HCC70), however, for the toxic compounds, IC₅₀ values ranged from 11.0 to 30.5 μM. Preliminary structure-activity relationships revealed the basic oxazine sub-ring and lipophilic benzene substituents to be conducive for biological efficacy of the ferrocenyl 1,3-benzoxazines reported in the study. DNA interaction studies performed on the most promising compound 4c suggested that DNA damage may be one possible mode of action of this class of compounds.