Benzoquinoline Derivatives: An Attractive Approach to Newly Small Molecules with Anticancer Activity

N-Heterocycles as Promising Antiviral Agents: A Comprehensive Overview

Viruses are a real threat to every organism at any stage of life leading to extensive infections and casualties. N-heterocycles can affect the viral life cycle at many points, including viral entrance into host cells, viral genome replication, and the production of novel viral species. Certain N-heterocycles can also stimulate the host's immune system, producing antiviral cytokines and chemokines that can stop the reproduction of viruses. This review focused on recent five- or six-membered synthetic N-heterocyclic molecules showing antiviral activity through SAR analyses. The review will assist in identifying robust scaffolds that might be utilized to create effective antiviral drugs with either no or few side effects.

The Effective Synthesis of New Benzoquinoline Derivatives as Small Molecules with Anticancer Activity

In this study, some novel benzo[c]quinoline derivatives were synthesized, their structural characteristics were described, and their in vitro anticancer efficacy was investigated. The synthesis involves an initial quaternization of the nitrogen atom from benzo[c]quinoline and then a [3+2] dipolar cycloaddition reaction of the in situ formed ylide. The effectiveness of synthesis using traditional thermal heating (TH) compared to microwave (MW) and ultrasound (US) irradiation was investigated in detail. The setup of a reaction under MW or US irradiation offers a number of additional benefits: higher yields, a reduction in the amount of solvent used compared to TH, a reduction in the reaction time from hours to minutes, and a reduction in the amount of energy consumed. The structure of all the obtained compounds was proved by several spectral techniques (FTIR, HRMS, and NMR). All benzo[c]quinoline derivatives (quaternary salts and cycloadducts) along with ten other benzo[f]quinoline derivatives (quaternary salts and cycloadducts), previously obtained, were tested in an in vitro single-dose anticancer experiment. The results demonstrated that the cycloadducts 5a-c and 6a-c exhibit stronger anticancer activity than quaternary salts 3a-c. The most active compound is compound 5a, with anticancer activity on most of the cell lines studied, while the second most active compound is 6c, showing significant lethality for the SR leukemia cell line (17%). Structure-activity relationship (SAR) correlations are also included in the study.

Synthesis and Antioxidant Activity of Some Benzoquinoline-Based Heterocycles Derived from 2-((3-Chlorobenzo[f]quinolin-2-yl)methylene)hydrazine-1-carbothioamide

A new series of benzoquinoline-based heterocycles was synthesized utilizing the building block synthon, 2-((3-chlorobenzo[f]quinolin-2-yl)methylene)hydrazine-1-carbothioamide via the condensation of 3-chlorobenzo[f]quinoline-2-carbaldehyde with thiosemicarbazide. The titled thiosemicarbazone scaffold was conducted with some carbon-centered electrophilic reagents such as acetic anhydride, chloroacetyl chloride, chloroacetic acid, 2-bromo-1-(3-nitrophenyl)ethan-1-one, 2-chloro-N-phenylacetamide, and dimethyl but-2-ynedioate to achieve triazolethione, imidazolone, thiazolidinone, and thiazole derivatives. In turn, the hydrazinolysis of this substrate did not proceed as expected but it afforded the azine derivative. The antioxidant activity screening of the produced compounds revealed that thiazole and triazolethione derivatives were the most potent.

Increased Free Radical Generation during the Interaction of a Quinone-Quinoline Chelator with Metal Ions and the Enhancing Effect of Light

Schiff bases and similar molecules forming metal complexes may cause redox effects, which may also be influenced by light. Anthraquinones such as doxorubicin and idarubicin are widely used antitumor agents, which can generate reactive oxygen species (ROS), stimulated by both the presence of iron and copper ions and also by light. The generated ROS can cause DNA scission, cell membrane oxidation, and many other toxic effects. The redox activity of the quinone-quinoline chelator 2-phenyl-4-(butylamino)naphtho [2,3-h]quinoline-7,12-dione (Q1) was investigated in the presence of iron, copper, and zinc. The influence of light in these interactions was also examined. The chemically induced dynamic nuclear polarization (CIDNP), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) methods were used to elucidate the molecular changes and ROS generation effects of the Q1 metal interactions. A model electron transfer reaction system between 1,4-dihydropyridine and Q1 was utilized to demonstrate that the chelate complexes of Q1 with both Fe(III) and Cu(II) ions were more redox active than Q1 itself. Similarly, CIDNP and NMR data showed that the concentration dependence of the free radicals yield is much higher in the presence of Fe(III) and Cu(II) ions, in comparison to Zn(II), and also that it increased in the presence of light. These findings underline the role of transition metal ions and Q1 in cyclic redox chain reactions and increase the prospect of the development of copper- and iron-based chelating agents, including Q1 and its derivatives, for anticancer therapy. Furthermore, these findings also signify the effect of light on enhancing ROS formation by Q1 and the prospect of utilizing such information for designing target specific anticancer drugs for photodynamic therapy.

Recent Advances in the Green Synthesis of Active N-Heterocycles and Their Biological Activities

N-heterocyclic scaffolds represent a privileged architecture in the process of drug design and development. It has widespread occurrence in synthetic and natural products, either those that are established or progressing as potent drug candidates. Additionally, numerous novel N-heterocyclic analogues with remarkable physiological significance and extended pharmaceutical applications are escalating progressively. Hence, the classical synthetic protocols need to be improvised according to modern requirements for efficient and eco-friendly approaches. Numerous methodologies and technologies emerged to address the green and sustainable production of various pharmaceutically and medicinally important N-heterocyclic compounds in last few years. In this context, the current review unveils greener alternatives for direct access to categorically differentiated N-heterocyclic derivatives and its application in the establishment of biologically active potent molecules for drug design. The green and sustainable methods accentuated in this review includes microwave-assisted reactions, solvent-free approaches, heterogeneous catalysis, ultrasound reactions, and biocatalysis.