The Relevance and Insights on 1,4-Naphthoquinones as Antimicrobial and Antitumoral Molecules: A Systematic Review

Natural product derivatives are essential in searching for compounds with important chemical, biological, and medical applications. Naphthoquinones are secondary metabolites found in plants and are used in traditional medicine to treat diverse human diseases. Considering this, the synthesis of naphthoquinone derivatives has been explored to contain compounds with potential biological activity. It has been reported that the chemical modification of naphthoquinones improves their pharmacological properties by introducing amines, amino acids, furan, pyran, pyrazole, triazole, indole, among other chemical groups. In this systematic review, we summarized the preparation of nitrogen naphthoquinones derivatives and discussed their biological effect associated with redox properties and other mechanisms. Preclinical evaluation of antibacterial and/or antitumoral naphthoquinones derivatives is included because cancer is a worldwide health problem, and there is a lack of effective drugs against multidrug-resistant bacteria. The information presented herein indicates that naphthoquinone derivatives could be considered for further studies to provide drugs efficient in treating cancer and multidrug-resistant bacteria.


Introduction
Natural products have played a major role in medicinal chemistry for several years. Numerous naturally occurring compounds are an important source of new drugs used to treat some human diseases. The remarkable structural diversity of natural products offers a broad field to discover new compounds with important applications in chemistry, biology, and medicine [1].
Due to the extensive use of pharmaceutical compounds in medicinal treatment, different microorganisms have emerged with enhanced resistance. In addition, many of these compounds have shown strong and adverse secondary effects in humans. As a result, there has been an exponential increase in the efforts to synthesize novel antimicrobial and anticancer agents [2][3][4][5]. Derivatives of natural compounds are an excellent alternative for medicinal treatment since they have been demonstrated to have minor adverse secondary effects compared with synthetic compounds [6].
Based on their structure, quinones have been classified as benzoquinones (containing one ring), naphthoquinones (containing two rings), or anthraquinones (containing three rings). They are extensively distributed in nature and can be found in plants, fungi, algae, and bacteria [7,8]. They constitute a large group of natural and synthetic compounds with To enhance the biological effects induced by NQs, some approaches include incorporating two biologically active groups in the same molecule. For instance, several compounds containing NQ and triazole nuclei in their structure have shown a more potent  Many biologically active compounds contain an indole heterocyclic structure [22][23][24]. Examples of this type of compound are mitomycin A 10 and 7-methoxymitosene 11 ( Figure 1). Indole is a fundamental structure in medicinal chemistry since it binds to multiple receptors with high affinity. As a result, different compounds containing substituted indole and quinone in their structure show diverse biological activity. The indole quinone subunit is an important framework of the mitomycin family of antitumor agents [22][23][24][25]. Hence, efforts to develop methods to assemble polycyclic compounds containing pyrrole and quinone have been conducted by researchers [26,32]. Among them, pyrido [2,3-d]pyrimidine 12 and phenazine 13 ring systems (Figure 1) are principal skeletons among many pharmaceutical scaffolds with applications in synthetic and medicinal chemistry.
To enhance the biological effects induced by NQs, some approaches include incorporating two biologically active groups in the same molecule. For instance, several compounds containing NQ and triazole nuclei in their structure have shown a more potent antibacterial effect than the active groups alone. Therefore, since both groups inhibit bacteria independently, a synergic effect must occur to enhance biological activity [27][28][29][30][31].
This comprehensive review aims to present the obtention of several nitrogen NQ derivatives reported in the literature as potential antibacterial and/or antitumoral agents, along with their preclinical evaluations and the proposed biological mechanisms induced by NQs. The authors used the ISI Web of Knowledge as the principal search tool for this revision. The search for articles containing obtention of nitrogen NQ derivatives included: "1,4-naphthoquinone", "amino acid", "Mannich base", "1,4 Michael addition", and "triazole" as well as patents and conference papers were excluded, then 75 articles, including reviews and original articles, were considered for Sections 1 and 2 of this paper, with Section 1 as the introduction and Section 2 discussing the chemical modification of NQ structures. Section 3 shows the pharmaceutical relevance and evidence on the antitumoral and antibacterial effects of NQs in preclinical assays focusing on the antibacterial and antitumor mechanisms proposed in the literature according to evidence at the cellular and molecular levels. Searching with the words "1,4-naphthoquinone", "ROS", "antibacterial", "apoptosis", "necrosis", and "docking study", 17 articles were considered, excluding conference papers and patents. Additionally, three articles were revised to explain oxidative stress. The search was restricted to the past ten years. Lastly, Section 5 discusses the biological evaluations of nitrogen NQ derivatives and aims to collect information on the preclinical evaluations; thus, there was a total of 37 articles in a search including the words "naphthoquinone", "antiviral", "antimalarial", "antitumor", and "antibacterial" and excluding paper conferences, patents, books, and reviews.

Chemical Modification of NQs Structures with Nitrogen Groups
Due to the biological relevance, the reactions of several nucleophilic atoms with an NQ ring have been extensively studied because the biological activity is related to their redox properties, which can be modulated by the ring substitution [7]. There are two general ways to modify the NQ ring with nucleophilic atoms: (1) Michael 1,4-addition and (2) nucleophilic substitution ( Figure 2). evaluations of nitrogen NQ derivatives and aims to collect information on the preclinical evaluations; thus, there was a total of 37 articles in a search including the words "naphthoquinone", "antiviral", "antimalarial, "antitumor", and "antibacterial" and excluding paper conferences, patents, books, and reviews.
Furthermore, anilino-1,4-naphthoquinone derivatives are compounds with a particular focus due to several biological properties. In the last years, several derivatives have been reported. Campora et al. (2021) reported the synthesis of NQ derivatives bearing hydrophobic moieties as promising candidates for Alzheimer's disease therapy [62]. Mahalap- Recently, Kumari et al., 2022, reported the indole-fused nitrogen heterocycles by two-step methodology, directly modifying the NQ ring. This compound can be used as solid-state fluorescence material ( Figure 13) [60].  The nucleophilic substitution of 2,3-dichloro-1,4-naphthoquinone is a synthetic strategy for introducing nitrogen, oxygen, carbon, sulfur, and selenium nucleophiles at C2 and C3 positions [61].
Furthermore, anilino-1,4-naphthoquinone derivatives are compounds with a particular focus due to several biological properties. In the last years, several derivatives have been reported. Campora et al. (2021) reported the synthesis of NQ derivatives bearing hydrophobic moieties as promising candidates for Alzheimer's disease therapy [62]. Mahalap- The nucleophilic substitution of 2,3-dichloro-1,4-naphthoquinone is a synthetic strategy for introducing nitrogen, oxygen, carbon, sulfur, and selenium nucleophiles at C2 and C3 positions [61].

Pharmaceutical Relevance and Evidence on the Antitumoral and Antibacterial Effects of NQs in Preclinical Assays
In several cases, the biological activity of NQ derivatives has been explained in terms of their physicochemical property to easily accept one or two electrons to generate a semiquinone or a dianion, respectively ( Figure 16). In addition, they can generate a 1,4-naphthodiol 14 by adding protons under solution conditions.
Quinone derivatives can interact with biological structures through several mechanisms. Firstly, quinones have a strong electrophilic character and can form covalent bonds. In solution, these molecules can easily undergo reversible oxidation-reduction reactions. Consequently, they can generate highly reactive oxygen species (ROS) and inhibit electron

Pharmaceutical Relevance and Evidence on the Antitumoral and Antibacterial Effects of NQs in Preclinical Assays
In several cases, the biological activity of NQ derivatives has been explained in terms of their physicochemical property to easily accept one or two electrons to generate a semiquinone or a dianion, respectively ( Figure 16). In addition, they can generate a 1,4naphthodiol 14 by adding protons under solution conditions.

Pharmaceutical Relevance and Evidence on the Antitumoral and Antibacterial Effects of NQs in Preclinical Assays
In several cases, the biological activity of NQ derivatives has been explained in terms of their physicochemical property to easily accept one or two electrons to generate a semiquinone or a dianion, respectively ( Figure 16). In addition, they can generate a 1,4-naphthodiol 14 by adding protons under solution conditions.
Quinone derivatives can interact with biological structures through several mechanisms. Firstly, quinones have a strong electrophilic character and can form covalent bonds. In solution, these molecules can easily undergo reversible oxidation-reduction reactions. Consequently, they can generate highly reactive oxygen species (ROS) and inhibit electron Quinone derivatives can interact with biological structures through several mechanisms. Firstly, quinones have a strong electrophilic character and can form covalent bonds. In solution, these molecules can easily undergo reversible oxidation-reduction reactions. Consequently, they can generate highly reactive oxygen species (ROS) and inhibit electron transport processes and different types of enzymes, such as topoisomerases.
At the cellular level, the biological activity of NQs has been associated with their redox properties ( Figure 17) [10]. Upon acceptance of one or two electrons, the NQ ring easily generates two highly reactive intermediates, namely a semiquinone or a dianion, which are oxidized upon exposure to oxygen and generate several ROS such as superoxide (O2 •-), hydroxyl radical ( • OH), and hydrogen peroxide (H 2 O 2 ). These latter chemical species can quickly diffuse through membranes, causing cytotoxicity. In addition, ROS quickly induce oxidative stress and apoptosis in cells since they cause damage to biomolecules, such as DNA, proteins, and lipids. transport processes and different types of enzymes, such as topoisomerases. Since many quinones have a planar structure, they can function as DNA-intercalating agents [7,10,11,71]. At the cellular level, the biological activity of NQs has been associated with their redox properties ( Figure 17) [10]. Upon acceptance of one or two electrons, the NQ ring easily generates two highly reactive intermediates, namely a semiquinone or a dianion, which are oxidized upon exposure to oxygen and generate several ROS such as superoxide (O2 •-), hydroxyl radical ( • OH), and hydrogen peroxide (H2O2). These latter chemical species can quickly diffuse through membranes, causing cytotoxicity. In addition, ROS quickly induce oxidative stress and apoptosis in cells since they cause damage to biomolecules, such as DNA, proteins, and lipids. The redox properties and reactivity of a given NQ can be modified by placing different substituents with electron acceptor or electron donor characters in the structure. Therefore, developing easy, fast, and efficient methods to synthesize novel NQ derivatives to find novel compounds with enhanced and adequate biological activity is essential.

Antitumoral and Antimicrobial Mechanisms of NQs
NQ molecules, either from natural sources or semisynthetic, exhibit antitumoral and antimicrobial effects in several biomodels, where some action mechanisms have been demonstrated, such as ROS imbalance, alteration of mitochondrial respiration in tumor cells and bacteria, DNA damage (by alkylation or intercalation), inhibition of topoisomerase II enzyme, among others.

REDOX Imbalance (ROS), Alteration of Mitochondrial Respiration, and Other Mechanisms Induced by NQs in Tumor Cells
As previously mentioned, ROS are highly reactive and unstable molecules. Some of them are more reactive since they have an unpaired electron, for example, O2 •-, peroxyl (RO2 • ), hydroxyl (HO2 • ), hydroperoxyl (HO • ), and alkoxyl (RO • ). In living organisms, the primary source of ROS is mitochondrial respiration, where electrons are transferred between protein complexes to produce energy. Some electrons will react with O2 to generate O2 •-. The ROS levels are controlled by enzymes, including superoxide dismutase, catalase, glutathione peroxidase, and non-enzymatic antioxidants such as glutathione, vitamins C and E, and any other molecule that could quench free radicals. An imbalance of ROS levels leads to macromolecular damage associated with aging and chronic diseases [72]. However, some physiological conditions trigger the release of ROS by the immune cells to fight against microorganisms and tumor cells. If the production of ROS overpasses the ability of enzymes such as catalase to degrade ROS, then various alterations in the cell signaling lead to cell damage via autophagic cell death, apoptosis, or necrosis (either to microorganisms The redox properties and reactivity of a given NQ can be modified by placing different substituents with electron acceptor or electron donor characters in the structure. Therefore, developing easy, fast, and efficient methods to synthesize novel NQ derivatives to find novel compounds with enhanced and adequate biological activity is essential.

Antitumoral and Antimicrobial Mechanisms of NQs
NQ molecules, either from natural sources or semisynthetic, exhibit antitumoral and antimicrobial effects in several biomodels, where some action mechanisms have been demonstrated, such as ROS imbalance, alteration of mitochondrial respiration in tumor cells and bacteria, DNA damage (by alkylation or intercalation), inhibition of topoisomerase II enzyme, among others.

REDOX Imbalance (ROS), Alteration of Mitochondrial Respiration, and Other Mechanisms Induced by NQs in Tumor Cells
As previously mentioned, ROS are highly reactive and unstable molecules. Some of them are more reactive since they have an unpaired electron, for example, , and alkoxyl (RO • ). In living organisms, the primary source of ROS is mitochondrial respiration, where electrons are transferred between protein complexes to produce energy. Some electrons will react with O 2 to generate O 2 •− . The ROS levels are controlled by enzymes, including superoxide dismutase, catalase, glutathione peroxidase, and non-enzymatic antioxidants such as glutathione, vitamins C and E, and any other molecule that could quench free radicals. An imbalance of ROS levels leads to macromolecular damage associated with aging and chronic diseases [72]. However, some physiological conditions trigger the release of ROS by the immune cells to fight against microorganisms and tumor cells. If the production of ROS overpasses the ability of enzymes such as catalase to degrade ROS, then various alterations in the cell signaling lead to cell damage via autophagic cell death, apoptosis, or necrosis (either to microorganisms or tumor cells). In this context, NQs have been extensively reported as a molecule that increases intracellular ROS by producing free electrons in the quinonesemiquinone reaction ( Figure 18). or tumor cells). In this context, NQs have been extensively reported as a molecule that increases intracellular ROS by producing free electrons in the quinone-semiquinone reaction ( Figure 18). It is well studied that an excess of ROS can alter signaling and gene expression and, consequently, induce tumors; however, ROS are also important in triggering apoptosis. ROS can interact with proteins, such as (1) phosphatases to induce their inhibition, (2) protein kinases (for inhibition or activation) of the Src family, (3) small G proteins, (4) tyrosine kinase receptors of growth factors, (5) and components that induce apoptosis, c-Jun N-terminal kinase (JNK) and p38 kinase (p38MAPK). For example, a small increment in the ROS levels activates the peptidase inhibitor 3-serine/threonine kinase 1 (PI3-K/Akt) pathway; if the ROS levels continue increasing, they trigger p38MAPK-dependent apoptosis [74].
As previously mentioned, the NQ structure undergoes transition from a quinone-like structure to semiquinone by one-electron reduction, and in a second step, to hydroquinone. This chemical reaction catalyzes the NADH and O2 redox circuit to enhance the intracellular ROS, and several authors have described their impact on cancer cells. For instance, Vukic et al., 2020, evaluated α-methylbutyrylshikonin 15, acetylshikonin 16, and β-hydroxyisovalerylshikonin 17 ( Figure 19) as prooxidant compounds in the potential treatment of cancer. The evaluation showed an increment in the superoxide anion (O2 •-) and oxidized glutathione levels in human colon cancer cells HCT-116 and MDA-MB-231 cells (regarding non-treated cells) when cultures were treated with 0.1 to 100 µ g/mL of NQ derivatives for 24 and 48 h. The authors also reported that levels of antioxidant molecules reduced glutathione (GSH) in the cells treated with any of the NQ derivatives, suggesting that all three derivatives induce oxidative stress [75]. Moreover, Majine et al., 2019, treated C6 glioma cells from rats with natural NQs (10 to 1000 µ M): lawsone 3 and plumbagin 4 ( Figure 1) and menadione (2-methyl-1,4-naphthoquinone) (Figure 7). The intracellular ROS meas- It is well studied that an excess of ROS can alter signaling and gene expression and, consequently, induce tumors; however, ROS are also important in triggering apoptosis. ROS can interact with proteins, such as (1) phosphatases to induce their inhibition, (2) protein kinases (for inhibition or activation) of the Src family, (3) small G proteins, (4) tyrosine kinase receptors of growth factors, (5) and components that induce apoptosis, c-Jun N-terminal kinase (JNK) and p38 kinase (p38MAPK). For example, a small increment in the ROS levels activates the peptidase inhibitor 3-serine/threonine kinase 1 (PI3-K/Akt) pathway; if the ROS levels continue increasing, they trigger p38MAPK-dependent apoptosis [74].
As previously mentioned, the NQ structure undergoes transition from a quinonelike structure to semiquinone by one-electron reduction, and in a second step, to hydroquinone. This chemical reaction catalyzes the NADH and O 2 redox circuit to enhance the intracellular ROS, and several authors have described their impact on cancer cells. For instance, Vukic et al., 2020, evaluated α-methylbutyrylshikonin 15, acetylshikonin 16, and βhydroxyisovalerylshikonin 17 ( Figure 19) as prooxidant compounds in the potential treatment of cancer. The evaluation showed an increment in the superoxide anion (O 2 •− ) and oxidized glutathione levels in human colon cancer cells HCT-116 and MDA-MB-231 cells (regarding non-treated cells) when cultures were treated with 0.1 to 100 µg/mL of NQ derivatives for 24 and 48 h. The authors also reported that levels of antioxidant molecules reduced glutathione (GSH) in the cells treated with any of the NQ derivatives, suggesting that all three derivatives induce oxidative stress [75]. Moreover, Majine et al., 2019, treated C6 glioma cells from rats with natural NQs (10 to 1000 µM): lawsone 3 and plumbagin 4 ( Figure 1) and menadione (2-methyl-1,4-naphthoquinone) (Figure 7). The intracellular ROS measured by fluorometry with 2 ,7 -dichlorofluorescein diacetate (DCFH-DA) showed a concentration-dependent increment of ROS levels after 3 h of treatment with plumbagin and menadione between 12 and 70% for control (no treatment). However, lawsone treatments reduced the intracellular ROS levels, and these results correlated with the cell viability since plumbagin and menadione (5 to 20 µM) treatments reduced viable cells between 20 and 95%. In comparison, lawsone reduced cell viability by 20 to 40% only when concentrations were from 250 to 1000 µM. The considerable decrease in cell viability was via necrosis. Then, the authors reported that levels of ROS induced by plumbagin and menadione also alter mitochondrial respiration and oxidative phosphorylation and completely uncouple oxidation from phosphorylation (alterations in the electron transport to produce ATP); hence, ATP production decreases, and as a consequence, the necrotic process begins [76].  Due to the aromatic structure of NQs, they may also interact with DNA and proteins, altering temporally or permanently the biomolecule's functions. Espinosa-Bustos et al., 2020, evaluated by cyclic voltammograms the interaction of modified 2-arylpiperidinyl-1,4-naphthoquinone compounds 22, 23, 24 (50 µ M) ( Figure 19) with dsDNA (25 to 100 µ L mL −1 ) at 37 °C , pH 7.2 for 45 min. The current peaks related to redox activity for all three compounds decayed as dsDNA concentration increased. Controls showed that free NQ derivatives reduced more easily in the absence of dsDNA. Computational studies evidenced interactions by either covalent or non-covalent interaction of NQ and the DNA structure [80]. On the other hand, the redox NQs activity is also one of the mechanisms affecting tumor cells. Researchers have proposed the coordination of NQs with metals to exert redox activity and interaction with biomolecules. Kosiha Figure 19) that hydrogen peroxide levels and cytotoxicity (IC 50 0.3-0.5 µM) for human lung carcinoma cell lines A549 were more significant for the SkQN 18 compound than MitoK3 19 in mitochondria isolated from rat heart and liver mitochondria. Both compounds (5 to 25 µM) achieved access into the inner mitochondrial membrane, exerted uncoupling activity and hence inhibited ATP production. Additionally, at a concentration of 3 µM, SkQN 18 and MitoK3 19 induced mitochondrial permeability transition pore opening, an important trigger for apoptosis and necrosis [77]. Wang  (apoptotic rate between 40 and 60%). The same treatment with BQ 20 and QO 21 decreases the levels of Bcl-2, a protein that sequesters proforms of death/driving cysteine proteases (caspases), hence preventing apoptosis [78]. Additionally, BQ 20 and QO 21 increase the levels of biomarkers associated with apoptosis: Bcl-2-associated death promoter (BAD), cleaved-caspase-3 (cle-cas-3), and cleavage of poly(ADPribose) polymerase (cle-PAPR). The authors also reported the depletion in the Akt expression levels, suggesting that BQ 20 and QO 21 induced G2/M phase cell cycle arrest in the AGS cells, hence acting on the apoptotic process [79].

NQs Alter the ROS Levels and Membrane Integrity and Can Chelate Metals Ions in Bacteria Cells
NQs trigger similar mechanisms in microorganisms, such as bacteria. In the past years, the chemical modification of NQs has been conducted to enhance the selectivity and antibacterial action of NQs. This is the case of Song et al., 2020, report for a lawsone derivative 26 (Figure 19), which can alter the ROS levels and induce cell membrane damage and chelation of intracellular iron ions in a methicillin-resistant Staphylococcus aureus (MRSA) model. When MRSA was exposed to 26 (16 µM, 4xMIC, 60 min), propidium iodide (a membrane-impermeable dye) uptake significantly increased, suggesting that the semisynthetic molecule can alter the bacteria cell membrane more effectively than vancomycin and lawsone. The authors linked the cell membrane alterations to intracellular ROS levels increasing (two-fold for nontreated bacteria, 60 min) in MRSA. Moreover, the higher the concentration of 26 in the treatments, the lower the intracellular ion iron levels. The bacteria viability was rescued when an excess of Fe 3+ was incorporated into the MRSA cultures, suggesting that NQ derivatives could chelate metal ions [82].
Another study considered three NQ derivatives: N- Figure 19) for antibacterial tests in S. aureus, Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae, finding MIC to be between 15.6 and 500 µg/mL. Ravichandiran et al., 2019, also reported that the levels of intracellular ROS determined by DCFH-DA fluorescent dye staining were equal in fluorescence intensity for NQs (15 to 31 µg/mL) in E. coli to the treatment in the same bacteria with streptomycin (1.9 µg/mL), indicating that antibacterial activity of NQ derivatives is led by oxidative stress caused by ROS [83].

Computational Studies in the Search for NQ Mechanisms against Cancer Cells and Bacteria
To understand the possible biological mechanistic action triggered by different NQ chemical structures, structure-activity relationship (SAR) and molecular docking studies are relevant. Firstly, SAR studies have made it possible to know that the position of substituents is critical for antibacterial activity. In a SAR study, Wellington et al., 2019, reported that the group fluoro in position C3 exhibited better MIC (31.3 µg/mL) against E. coli, while fluoro in position C4 decreased the antibacterial activity about three times. Removing fluoro groups and adding 3-sulfanylpropanoic acid reduce the MIC by about seven times [84]. Similar evidence presented by Sánchez-Calvo et al., 2016, states that the halogens chloro and bromo in position C2 enhance the MIC (2 and 16 µg/mL, respectively) against Candida krusei. The authors also discuss that a single OH in position C5 is essential in antibacterial activity, while methoxylation in C5 and/or C8 is inactive for yeasts [85].
Moreover, NQ reports are frequently accompanied by molecular docking, a computational tool to understand the interaction between NQs and biological ligands. In this sense, molecular docking studies have shown that some NQs, such as juglone 2, propionyl juglone, and 2-acetyl-8-methoxy-1,4-naphthoquinone (Figure 1), possess inhibitory activity against SARS-CoV-2's main proteinase since NQ molecules fit into the proteinase through hydrogen bonds with amino acid residues. Jiahua et al., 2021, showed the strongest interaction for 2-acetyl-8-methoxy-1,4-naphthoquinone, which presented hydrogen bonding interactions with His41, Gly143, and Glu166, which explain the highest inhibitory activity against the proteinase [86].
On the other hand, most of the information regarding NQ-biomolecule interactions comes from molecular docking studies. In this sense, Ravichandiran et al., 2019, carried out a molecular docking study to determine if compound 29 ( Figure 19) interacts with the E. coli DmsD protein, which blocks redox proteins from early transport. The interactions have an affinity energy of 2.63 kcal/mol with hydrogen-bonding and π-π stacking forces in the active site of ARG A15, reinforcing the evidence of NQ-protein interactions and ROS imbalance as antibacterial activity and suggesting that NQ derivatives can alter bacteria replication [83].
Thus, it is relevant to know the potential targets in bacteria and cells to increase the efficacy in synthesizing active NQs. Mohamady Figure 20). The molecular docking of these quinones with the ATPase domain of the human topoisomerase IIα predicted that these compounds interact with Ser-148, Ser-149, Asn-150, and Asn-91 residues through hydrogen bonds. The synergy between experimental and computational studies allowed the authors to elucidate the possible inhibition mechanism of ATPase [88].
Recently, a group of 2-amino-4H-naphthopyran-3-carbonitrile NQ derivatives 37-44 was evaluated with a similar perspective by Amani et al., 2023. The authors first evaluated the anticancer activity in HCT116 human colon cancer cell lines. Then, those compounds with the highest cytotoxic activity were taken to assess their interactions in a docking study with the human tyrosine kinase CK-2 (a protein involved in cell growth and proliferation). The findings pointed out that NQ derivatives require a planar aromatic region with substitution to form electrostatic interactions with Lys68 and Asp175 residues. A second interaction was revealed as a non-coplanar aromatic region with π-π stacking forces with His160 [89].
Current experimental and computational evidence highlights several NQ derivatives as antitumoral and antibacterial potential drugs, with more than a single mechanism in eukaryotic and prokaryotic cells.

Biological Evaluations of Nitrogen NQ Derivatives
The activity of a given substituted anilino naphthoquinone has been associated with its redox properties. Depending on the substituents in the aromatic ring, the amino group in the naphthoquinone can modulate its physicochemical properties and modify its biological activity and interactions with biomolecules [33,[36][37][38]. The secondary amine, 2-anilino-1,4naphthoquinone, is a basic structure present in many natural and synthetic compounds. Many of these compounds have shown important biological properties as antibacterial, antifungal, antimalarial, or anticancer agents. Lawsone Mannich bases are 2-hydroxy-3-(aminomethyl)-1,4-naphthoquinone compounds with important biological activities such as antiparasitic, antibacterial, anticancer, and antiviral, which have a particular interest in medicinal chemistry because the Mannich reaction forms a C-C bond with nitrogencontaining derivatives. This section presents molecules with promissory activity, as shown in Table 1 [31,[42][43][44][45][90][91][92]. Table 1. Biological evaluations of aniline-, -amino acids-and Manich bases naphthoquinone derivatives.

Conclusions
As shown in this review, the redox properties of NQs produce ROS as superoxide, hydroxyl radical, and hydrogen peroxide; ROS can trigger autophagic cell death, chemo-

Conclusions
As shown in this review, the redox properties of NQs produce ROS as superoxide, hydroxyl radical, and hydrogen peroxide; ROS can trigger autophagic cell death, chemosensitive, apoptosis, and necrosis. Furthermore, NQ derivatives can induce cell membrane damage, generate intracellular chelation with metals as iron, and NQ derivatives that preserve the planar structure may intercalate with DNA. Thus, pieces of evidence in preclinical assays (mostly in vitro) highlight to NQs as potential antimicrobial and antitumoral drugs. However, to the knowledge of the authors, no clinical evaluations have been conducted, since NQs face some challenges: (1) low solubility and (2) potential cytotoxic effect over healthy eucaryotic cells. It seems that nitrogen NQ derivative compounds could face those disadvantages, and further studies, particularly rigorous toxicological evaluations, can reveal the new generation of NQs for commercial applications.