Synthesis of microwave-assisted carboxamides in Triton WR-1339-induced hyperlipidemic rats: possible hypolipidemic heterocyclic compounds.

The hypolipidemic effect of furan carboxamide derivatives was investigated using the Triton WR-1339 rat model. Nineteen compounds were synthesized, including furan-2-carboxamides of benzophenones and acetophenones (a(1-4)), anilines and amine derivatives (a(5-9)), picolinic-2-carboxamide derivatives of benzophenones and acetophenone (a(10-12)) and furan-2-carboxylate esters of benzophenones and acetophenones, substituted phenols and alcohols (b(1-7)). All the necessary steps were taken to synthesize, purify, and characterize these compounds. They were synthesized by reacting acyl chlorides of the heterocycles with their corresponding amines in the presence of pyridine and tert-butyl acetate. While the conventional heating method yielded acceptable yields for some of the reactions under reflux, the microwave synthesis reactor achieved significantly higher yields for others. Rats with hyperlipidemia were induced with Triton WR-1339 and then subjected to in vivo testing via an intraperitoneal injection of 200 mg kg-1 Triton WR-1339. The model was tested using an oral dose of bezafibrate (100 mg kg-1). After 7 hours of treatment with Triton, the new derivatives represented by compounds a(1-2), a(4-5), a7, and a(10-12) showed significant activity against the complete lipid profile, including a decrease in triglyceride, total cholesterol, and low-density lipoprotein cholesterol and an increase in high-density lipoprotein cholesterol plasma levels. At 20 mg kg-1 dose, these compounds were superior to other lipid-lowering agents in reducing triglyceride levels and slightly increased high-density lipoprotein cholesterol levels. These results indicate a mutual mechanism of action of novel compounds with fibrates, where they have a marked effect on triglyceride and high-density lipoprotein cholesterol levels; for example, a5 causes a significant reduction (p 0.0001) of triglyceride levels by 86%, and a remarkable increase (p 0.0001) in high-density lipoprotein cholesterol plasma levels by 65% as compared to hyperlipidemic rats.

Discovery of potent 4-aminoquinoline hydrazone inhibitors of NRH:quinoneoxidoreductase-2 (NQO2).

(NRH):quinone oxidoreductase 2 (NQO2) is associated with various processes involved in cancer initiation and progression probably via the production of ROS during quinone metabolism. Thus, there is a need to develop inhibitors of NQO2 that are active in vitro and in vivo. As part of a strategy to achieve this we have used the 4-aminoquinoline backbone as a starting point and synthesized 21 novel analogues. The syntheses utilised p-anisidine with Meldrum's acid and trimethyl orthoacetate or trimethyl orthobenzoate to give the 4-hydrazin-quinoline scaffold, which was derivatised with aldehydes or acid chlorides to give hydrazone or hydrazide analogues, respectively. The hydrazones were the most potent inhibitors of NQO2 in cell free systems, some with low nano-molar IC50 values. Structure-activity analysis highlighted the importance of a small substituent at the 2-position of the 4-aminoquinoline ring, to reduce steric hindrance and improve engagement of the scaffold within the NQO2 active site. Cytotoxicity and NQO2-inhibitory activity in vitro was evaluated using ovarian cancer SKOV-3 and TOV-112 cells (expressing high and low levels of NQO2, respectively). Generally, the hydrazones were more toxic than hydrazide analogues and further, toxicity is unrelated to cellular NQO2 activity. Pharmacological inhibition of NQO2 in cells was measured using the toxicity of CB1954 as a surrogate end-point. Both the hydrazone and hydrazide derivatives are functionally active as inhibitors of NQO2 in the cells, but at different inhibitory potency levels. In particular, 4-((2-(6-methoxy-2-methylquinolin-4-yl)hydrazono)methyl)phenol has the greatest potency of any compound yet evaluated (53 nM), which is 50-fold lower than its toxicity IC50. This compound and some of its analogues could serve as useful pharmacological probes to determine the functional role of NQO2 in cancer development and response to therapy.

Evaluation of analogues of furan-amidines as inhibitors of NQO2.

Inhibitors of the enzyme NQO2 (NRH: quinone oxidoreductase 2) are of potential use in cancer chemotherapy and malaria. We have previously reported that non-symmetrical furan amidines are potent inhibitors of NQO2 and here novel analogues are evaluated. The furan ring has been changed to other heterocycles (imidazole, N-methylimidazole, oxazole, thiophene) and the amidine group has been replaced with imidate, reversed amidine, N-arylamide and amidoxime to probe NQO2 activity, improve solubility and decrease basicity of the lead furan amidine. All compounds were fully characterised spectroscopically and the structure of the unexpected product N-hydroxy-4-(5-methyl-4-phenylfuran-2-yl)benzamidine was established by X-ray crystallography. The analogues were evaluated for inhibition of NQO2, which showed lower activity than the lead furan amidine. The observed structure-activity relationship for the furan-amidine series with NQO2 was rationalized by preliminary molecular docking and binding mode analysis. In addition, the oxazole-amidine analogue inhibited the growth of Plasmodium falciparum with an IC50 value of 0.3 µM.

Non-symmetrical furan-amidines as novel leads for the treatment of cancer and malaria.

NRH:quinone oxidoreductase 2 enzyme (NQO2) is a potential therapeutic target in cancer and neurodegenerative diseases, with roles in either chemoprevention or chemotherapy. Here we report the design, synthesis and evaluation of non-symmetrical furan-amidines and their analogues as novel selective NQO2 inhibitors with reduced adverse off-target effects, such as binding to DNA. A pathway for the synthesis of the non-symmetrical furan-amidines was established from the corresponding 1,4-diketones. The synthesized non-symmetrical furan-amidines and their analogues showed potent NQO2 inhibition activity with nano-molar IC50 values. The most active compounds were non-symmetrical furan-amidines with meta- and para-nitro substitution on the aromatic ring, with IC50 values of 15 nM. In contrast to the symmetric furan-amidines, which showed potent intercalation in the minor grooves of DNA, the synthesized non-symmetrical furan-amidines showed no affinity towards DNA, as demonstrated by DNA melting temperature experiments. In addition, Plasmodium parasites, which possess their own quinone oxidoreductase PfNDH2, were inhibited by the non-symmetrical furan-amidines, the most active possessing a para-fluoro substituent (IC50 9.6 nM). The high NQO2 inhibition activity and nanomolar antimalarial effect of some of these analogues suggest the lead compounds are worthy of further development and optimization as potential drugs for novel anti-cancer and antimalarial strategies.