# Pharmacological Profile of Quinoxalinone

Authors: Youssef Ramli; Ahmed Moussaif; Khalid Karrouchi; El Mokhtar Essassi
Journal: Journal of Chemistry
 (2014)

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## Abstract

Quinoxalinone and its derivatives are used in organic synthesis for building natural and designed synthetic compounds and they have been frequently utilized as suitable skeletons for the design of biologically active compound. This review covers updated information on the most active quinoxalinone derivatives that have been reported to show considerable pharmacological actions such as antimicrobial, anti-inflammatory, antidiabetic, antiviral, antitumor, and antitubercular activity. It can act as an important tool for chemists to develop newer quinoxalinone derivatives that may prove to be better agents in terms of efficacy and safety.


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## Body

## 1. Introduction

The quinoxalinones are a class of heterocyclic compounds with different applications in various fields; these have been studied intensively as important heterocyclic system for the synthesis of biologically active compounds ranging from herbicides and fungicides to therapeutically usable drugs. A literature survey identified several quinoxalinones derivatives in the development phase as potential new drugs. The versatility of the quinoxalinones skeleton, in addition to its relative chemical simplicity and accessibility, makes these chemicals amongst the most promising sources of bioactive compounds. This has led to the discovery of a wide variety of compounds that are of high interest from the point of view of antimicrobial, antifungal, antiviral, anti-inflammatory, and antitumor effects among others.


## 2. Antimicrobial Activity

Antimicrobial agents are essential for the treatment of a number of diseases of bacterial or fungal origin, and many such agents are used clinically and industrially. Recently, however, bacteria have acquired drug resistance and so the development of new antimicrobial agents is required [1–3]. A number of compounds based on nitrogen-containing heterocycles show antimicrobial activity and have been developed for clinical use [4]. Among the various classes of heterocyclic units, the quinoxaline ring has frequently been used as a component of various antibiotic molecules, such as hinomycin, levomycin, and actindeutin, which inhibit the growth of Gram-positive bacteria and are active against various transplantable tumors [5–7].Another notable activity of quinoxalinones is the antimicrobial one. In fact, Kotharkar and Shinde [8] have shown that 9,10-dimethyl-2-methoxy-6-oxo-7,12-dihydro-chromo-[3,4-b]quinoxaline 1 has both antibacterial and antifungal activities. In another study [9], it has been shown that quinoxalinones 2, 3, 4, and 5 (Figure 1) possess the same activities.Figure 1
Chemical structures of compounds tested.In the search for new antimicrobial agents, 2(1H)-quinoxalinones and their hexahydro derivatives were prepared [10]. Thiosemicarbazide 6 (Figure 2) derived from hexahydro-2(1H)-quinoxalinone showed a high in vitro antibacterial activity.Figure 2
Chemical structure of compound6.A series of 3-(3-oxo-3,4-dihydroquinoxalin-2-yl) propionic acid derivatives was synthesized and then treated with hydrazine hydrate to yield its hydrazones7 (Figure 3). This was further reacted with substituted aromatic aldehydes to produce final compounds 7a–r (Table 1). All the synthesized compounds were evaluated for their antimicrobial and anti-inflammatory activity [11].Table 1
List of compounds prepared7a–r.
Compounds
R
R1
Compounds
R
R1
7a
H
4-F-C6H4
7j
H
4-NO2-C6H4
7b
H
2-Cl-C6H4
7k
CH3
4-F-C6H4
7c
H
3-Cl-C6H4
7l
CH3
2-Cl-C6H4
7d
H
4-Cl-C6H4
7m
CH3
3-Cl-C6H4
7e
H
4-OH-C6H4
7n
CH3
4-Cl-C6H4
7f
H
4-OCH3-C6H4
7o
CH3
4-OH-C6H4
7g
H
3,4-OCH3-C6H3
7p
CH3
4-OCH3-C6H4
7h
H
3,4,5-OCH3-C6H2
7q
CH3
2-NO2-C6H4
7i
H
2-NO2-C6H4
7r
CH3
4-NO2-C6H4Figure 3
Chemical structures of compounds tested.Ishikawa et al. [12] synthesized some derivatives of 2,3-bis(bromomethyl)quinoxaline with substituents at the 6- and/or 7-positions and evaluated their activities against bacteria and fungi. Of the 12 compounds (Table 2), nine 9a–h, 9j, 9k showed antibacterial activity. The derivative 9g, which bears a trifluoromethyl group at the 6-position, showed the highest activity against Gram-positive bacteria, while 16c, which has a fluoro-group at the 6-position, showed the widest antifungal activity spectrum. However, only the derivative with an ethyl ester substitution 9k showed activity against Gram-negative bacteria (Figure 4 and Table 3).Table 2
List of compounds tested.
Compounds
R1
R2
Compounds
R1
R2
9a
CH3
CH3
9g
CF3
H
9b
CN
H
9h
NO2
H
9c
F
H
9i
CO2
H
9d
Cl
H
9j
CO2CH3
H
9e
Br
H
9k
CO2CH2CH3
H
9f
OCH3
H
9l
OH
HTable 3
Antifungal activities of compounds9a–l.
MIC (μg/mL)
R1
R2
Mold
Yeast
A. n.a
P. c.b
C. c.c
A. p.d
A. s.e
M. s.f
G. v.g
R. r.h
S. c.i
9a
CH3
CH3
>100
>100
>100
>100
>100
>100
>100
>100
>100
9b
CN
H
50
25
25
50
25
25
>100
100
50
9c
F
H
50
50
50
100
50
25
100
100
50
9d
Cl
H
50
100
25
>100
>100
50
>100
>100
>100
9e
Br
H
100
100
50
>100
>100
50
>100
>100
>100
9f
OCH3
H
50
>100
50
100
100
50
>100
>100
100
9g
CF3
H
50
50
100
50
100
25
>100
100
50
9h
NO2
H
100
100
50
100
25
50
100
>100
50
9i
COOH
H
>100
>100
>100
>100
>100
>100
>100
>100
>100
9j
CO2CH3
H
50
100
100
50
100
25
>100
>100
50
9k
CO2CH2CH3
H
>100
>100
>100
100
>100
100
>100
100
100
9l
OH
H
>100
>100
>100
>100
>100
>100
>100
>100
>100
aAspergillus niger, bPenicillium citrinum, cCladosporium cladosporioides, dAureobasidium pullulans, eAlternaria sp., fMucor spinescens, gGliocladium virens, hRhodotorula rubra, iSaccharomyces cerevisiae.Figure 4
Chemical strucure of compound9a–l.Seven derivatives of thiadiazolo[20,30:2,3]imidazo[4,5b] quinoxalines 10a–g were synthesized [13] for potential antimicrobial agents. The antimicrobial evaluation of the newly synthesized products against a broad spectrum of bacteria was performed using the disc diffusion technique and the agar streak dilution method. It was found that, among the synthesized compounds, only the unsubstituted and electron donating group containing molecules has shown better antimicrobial activity when compared to electron withdrawing compound on the phenyl group. Of all the synthesized compounds 10a, 10b, and 10d had shown good antibacterial and antifungal activity (Scheme 1).Scheme 1
Synthesis of compounds10a–g.The compound 2,6-dimethyl-3-f-quinoxaline 1,4-dioxide11f was found to inhibit 50% of Leishmania growth at 8.9 lM, with no impact against proliferative kidney cells and with low toxicity against THP-1 cells and murine macrophages. The compounds belonging to the propenone quinoxaline series were moderately active against T. cruzi. Among these compounds (Figure 5), two were particularly interesting, (2E)-1-(7-fluoro-3-methyl-4 quinoxalin-2-yl)-3-(3,4,5-trimethoxy-phenyl)-propenone and 12b (2E)-3-(3,4,5-trimethoxy-phenyl)-1-(3,6,7-trimethyl-quinoxalin-2-yl)-propenone 12f. The former possessed selective activity against proliferative cells (cancer and parasites) and was inactive against murine peritoneal macrophages; the latter was active against Leishmania and inactive against the other tested cells [14].Figure 5
Chemical structures of compounds tested.Novel 8-chloro-1,4-substituted-[1,2,4]triazolo[4,3-a]quinoxaline derivatives 13a–j have been synthesized by Suresh et al. [15] (Figure 6 and Table 4). All the above compounds were screened for antimicrobial activity and antioxidant activity and their bioassay showed them to possess significant antimicrobial activity and anti-oxidant activity.Table 4
List of compounds prepared.
Compound
R
R1
13a
13b
13c
13d
13e
13f
13g
13h
13i
13jFigure 6
Chemical structures of compounds13a–j.In an effort to develop potent antimicrobial agents, Ghadage and Shirote [16] have synthesized some substituted quinoxalin-2(1H)-one derivatives. Final derivatives 14a–e (Figure 7) were screened for their in vitro antibacterial activity against range of Gram positive and Gram-negative; also for their anti-fungal activity against a strain of Candida albicans species. It was found that all the selected compounds exhibit wide antimicrobial activity. Amongst these compounds, compound 14b was highly active against E. coli. The compounds 14d and compound 14c were highly active against P. aeruginosa and S. aureus. The compounds 14c and 14d were highly active against C. albicans.Figure 7
Chemical structures of compounds tested.A series of quinoxalines15a–g (Figure 8 and Table 5) screened for antibacterial activity among them compound 15a was displayed activity against E. coli, compounds 15d and 15f against P. mirabilis, compound15c against B. subtilis, and compound 15e against S. aureus shows maximum activity at 200 μg/disc [17].Table 5
List of compounds prepared.
a
b
c
d
e
F
g
R1
CH3
2-Furyl
CH3
2-Furyl
CH3
H
CH3
R2
Ph
2-Furyl
Ph
2-Furyl
Ph
Ph
Ph
R3
H
CH3
H
PhCO
PhCO
H
MeOPhCO
R4
H
CH3
Cl
H
H
CH3
H
X
N
C
C
C
C
C
CFigure 8
Chemical structures of compounds15a–g.A series of ethyl 2-[(3-methyl-2-oxoquinoxalin-1(2H)-yl)acetyl]-3-oxo-2,3-dihydro-1Hpyrazole-4-carboxylate derivatives16a–i (Figure 9 and Table 6) was prepared and evaluated for their antitubercular activities [18]. All compounds were screened for in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv (MTB). Minimum inhibitory concentrations were determined and interpreted for Mycobacterium tuberculosis H37Rv according to the procedure of the approved macrodilution reference method of antimicrobial susceptibility testing. Among all the compounds synthesized 16b, 16c, and 16f were found to be the most active compounds against MTB with MIC (25 μg/mL) [18].Table 6
List of compounds tested.
Compound
R
16a
16b
16c
16d
16e
16f
16g
16h
16iFigure 9
Chemical structures of compounds tested16a–i.A series of 2-quinoxalinone-3-hydrazone derivatives (Figure10) synthesized was evaluated for their antimicrobial activities [19]. The results showed that this skeletal framework exhibited marked potency as antimicrobial agents. The most active antibacterial agent was 3-{2-[1-(6-chloro-2-oxo-2H-chromen-3 yl) ethylidene]hydrazinyl}quinoxalin-2(1H)-one 23, while 3-[2-(propan-2 ylidene)hydrazinyl]quinoxalin-2(1H)-one 18, appeared to be the most active antifungal agent.Figure 10
Chemical structures of compounds17–33.The compound 1-methyl-7-nitro-4-(5-(piperidin-1-yl) pentyl)-3,4-dihydroquinoxalin-2(1H)-one34 (Figure 11) was evaluated [20] against a blood-induced infection with chloroquine-sensitive Plasmodium yoelii yoelii lethal strain in CD1 mice in a 4-day test scheme. The results obtained in this study showed that the infection outcome of P. yoelii yoelii-infected mice is affected by compound 34 by slowing down the parasite replication, retarding the patency time, and increasing their survival time. Although compound 34 was active at higher doses than chloroquine, these results leave a door open to the study of its structure in order to improve its antimalarial activity.Figure 11
Chemical structures of compound34.Some novel pyrido[2,3-g]quinoxalinones35–46 (Figure 12), variously substituted at the C-3 position, were synthesized [21], structurally determined, and submitted to a preliminary in vitro evaluation for antibacterial, anti-Candida activities (1). Results of the antimicrobial screening showed that all compounds, with the exception of 38, 43, and 44, exhibited interesting activity against all strains tested.Figure 12
Chemical structures of compounds tested.


## 3. Anti-Inflammatory Activity

In the search for new anti-inflammatory agents, 2(1H)-quinoxalinones and their hexahydro derivatives were prepared [10]. The 2(1H)-quinoxalinone derivative bearing 4-chlorophenyl-2,3-dihydrothiazole moiety 45 (Figure 13) exhibited the highest anti-inflammatory activity without causing any ulcer side effects like the selective COX-2 inhibitor celecoxib.Figure 13
Chemical structures of compound45.Burguete et al. [22] studied the anti-inflammatory and antioxidant activity of several quinoxalines. Compound 46 (Figure 14) presented the most interesting activity.Figure 14
Chemical structures of compounds46 and 47.Similarly, in the study of the same anti-inflammatory activity, Li et al. [23] have evaluated the activity of the quinoxaline 47 by varying R and R′ substituents. Compounds B1 and B2 (Figures 14 and 15) were found to be nonpeptide antagonists of the interleukin-8 molecule receptor, which is involved in several inflammatory diseases and cancer [23].Figure 15
Chemical structures of compounds tested.


## 4. Antiviral Activity

Since 2005, the World Health Organization (WHO) estimated that worldwide more than 40 million people were infected with the human immunodeficiency virus (HIV). In particular, South America is facing a rapidly growing number of HIV infections which require an effective antiviral therapy. Ideally, anti-HIV drugs should be highly selective and have good oral availability and favorable pharmacokinetics. Moreover, large-scale production, at low costs to make them accessible for patients in developing countries, would constitute a crucial advantageous feature. Several derivatives of quinoxaline display interesting activity against HIV as nonnucleosidic inhibitors of the reverse transcriptase (RT) [24, 25]. Some of quinoxalinone derivatives synthetized by Gris et al. [26] exhibited good inhibitor activity against some human tumoral cells and the lymphoma related to HIV-1. The studies against HIV were developed for compound 48e and the methyl ester of 49c, and no activity was observed, as compared to efavirenz, though it is worth mentioning that the assayed concentrations up to the order 10−6M were not cytotoxic. On the other hand, potential antitumoral activity of compounds 49a and 49b has been investigated in the National Cancer Institute (USA). Compound 49a displayed in vitro activity against a nonsmall lung cell line (EKVX) and human kidney cells (CL A498), while 49b displayed in vitro activity against central nervous system (CNS) human cells. However, the cytotoxicity shown in both cases was higher than the minimal required to continue the screening. 4c was evaluated by the Biological Evaluation committee (BEC). Findings indicated a higher activity against AIDS-related lymphoma than the reference compound employed by the NCI. Nevertheless, it did not reach the lower toxicity level to perform in vivo studies (Figure 16).Figure 16
Chemical structures of Compounds tested.Great efforts have been dedicated to the design of compounds acting as selective inhibitors of the HIV-1, and in this case a series of novel N4-(hetero)arylsulfonylquinoxalinonederivatives50 (Figure 17) way prepared by Xu et al. in a straight and efficient way [27]. Of all the synthesized compounds, five compounds exhibited potent anti-HIV-1 replication activities with IC50 value at the level of 10−7mol/L. Preliminary structure-activity relationships were studied in detail and that will shed light on the discovery of more potent nonnucleoside reverse-transcriptase inhibitors [27] (Table 7).Table 7
Antiviral activity of compounds50a–h.
Compound
R3
ArSO2
IC
50 (μM)
50a
H
Quinoline-8-sulfonyl
0.98
50b
H
3-Cyanobenzene-1-sulfonyl
>100
50c
H
2-Methyloxycarbonylthiophene-3-sulfonyl
2.02
50d
CH3
Quinoline-8-sulfonyl
7.0
50e
CH3
4-Nitrobenzene-1-sulfonyl
>100
50f
CH3
3-Cyanobenzene-1-sulfonyl
55
50g
CH3
2-Methyloxycarbonylthiophene-3-sulfonyl
0.2
50h
CH3
2,5-Dichlorothiophene-3-sulfonyl
>100Figure 17
Chemical strucure of compound50a–h.Similarly, other quinoxalinone derivatives have antiviral properties [28, 29]. Many studies have shown the activity of a few quinoxaline compounds towards the human immunodeficiency virus (HIV-1), including the 6,7-dimethyl-2-(pent-4-enyloxy)quinoxaline 52, [30] and 53, which not only inhibited HIV-1 RT, but also prevented its replication at the cellular membrane [31] (Figures 18 and 19, Table 8).Table 8
List of compounds tested.
Compound
R3
IC
50
(μM)
51a
H
2.02
51b
CH3
0.2
51c
C2H5
5.0
51d
CH2CH2SCH3
>100
51e
CH2COOCH3
>100Figure 18
Chemical structures of compounds51a–h.Figure 19
Chemical structures of compounds prepared.


## 5. Enzyme Inhibitory Activity

We will mention a few patents showing various activities of quinoxalinone, as an inhibitor of the kinase protein [32].The compound54 [33] is a new molecular macrocycle derived from the quinoxalin-2-one inhibitor of cyclin-dependent kinases CDK1, 2, 4, and 6, while the compound 55 [34] inhibiting glycogen phosphorylase is the enzyme responsible for the metabolism of glycogen to glucose since glucose is overproduced in patients suffering from diabetes (Figure 20).Figure 20
Chemical structures of compounds54 and 55.Imidazo[1,5-a]quinoxalines were synthesized that function as irreversible Bruton’s tyrosine kinase (BTK) inhibitors. The syntheses and SAR of this series of compounds are presented as well as the X-ray crystal structure of the lead compound56 in complex with a gate-keeper variant of ITK enzyme (Figures 21 and 22). The lead compound showed good in vivo efficacy in preclinical RA models [35].Figure 21
Chemical structure of compound56.Figure 22
X-ray structure of56 in complex with a gate-keeper variant of ITK enzyme in the ATP binding site.


## 6. Antitumor Activity

Multidrug resistance (MDR) is a critical issue in cancer chemotherapy. Overexpression of P-gp is the most frequent cause of MDR. P-gp, a transmembrane glycoprotein, functions as an ATP-dependent drug transporter which unilaterally transports intracellular drugs out of cells to acquire drug resistance. A range of agents that can reverse the MDR phenotype and restore drug sensitivity to cancer cells have been developed [36, 37]. However, most of these agents have proven to be intrinsic toxic and having undesired effects on the pharmacokinetics of accompanying anticancer drugs. For instance, initial attempts to develop MDR modulators focused on verapamil and cyclosporin A [38–40]; these compounds demonstrated excellent in vitro reversal of MDR but failed to achieve clinical success due to their toxicity and/or their alteration of the pharmacokinetics of the coadministered anticancer drugs [40, 41]. Screening 11,000 compounds from commercially available libraries, Lawrence et al. [42] identified several structural platforms with good potential as MDR antagonists. Among these, the 2 oxoquinoxaline or quinoxalinone scaffold showed promise as a versatile scaffold to study P-gp antagonist [42]. Sun et al. [43] have designed and synthesized a series of substituted 1,3-dimethyl-1H-quinoxalin-2-ones. They found that some of the compounds displayed potential inhibition effect on MDR of cancer.The compounds57 and 58 (Figure 23) are the novel substituted 1,3-dimethyl-1H-quinoxalin-2-ones with high reversal folds on multidrug resistance in K562/A02 cells. These compounds might be the candidate agents for reversing MDR of cancer.Figure 23
Chemical structures of compounds57 and 58.Quinoxalinone derivatives continue to be a standing interest of lot of research groups. So far, a great deal of data concerning the anticancer activity of more than 300 compounds constitute a library for the antifolic analogs [44–57]. During their investigation, Piras et al. [58] have taken into account as antifolate models either the classical methotrexate or the nonclassical trimetrexate as well as the corresponding dideazafolic derivatives. In this context they have proved that bioisosteric replacement of pteridine ring with Trifluoro-6-methylquinoxaline and trifluoro-7-quinoxaline affords a good substrate for the biological activity in the series of the classical antifolate analogs, whereas this was so in a few cases of the series of nonclassical ones. Another aspect being considered was also the bioisosteric replacement of 2-NH group with an oxygen that in some cases was of relevance in the anticancer activity. However, for development of the knowledge about the pharmacophoric pattern, the authors [58] thought to replace the 2-NH bridge in the above-cited series with oxygen on the ground that very recently American authors have found that quinoxalines bearing a 2-(4-substituted phenoxy) substituent were endowed with potent antitumor activity [59]. Thus, the list of compounds 59a–v (Figure 24 and Table 9) was prepared and the results of their activity presented in Table 10.Table 9
List of compounds prepared.
Compound
R
R1
R2
59a
H
6,7-F
OMe
59b
Ph
H
OMe
59c
2-Th
H
OMe
59d
COOEt
H
OMe
59e
COOEt
7-CF3
OMe
59f
COOEt
6,7-F
OMe
59g
Ph
H
OH
59h
2-Th
H
OH
59i
COOH
H
OH
59j
COOH
7-CF3
OH
59k
COOH
6,7-F
OH
59l
Ph
H
NHgluH
59m
2-Th
H
NHgluH
59n
CONHgluEt
H
NHgluH
59o
COOH
7-CF3
NHgluH
59p
CONHgluEt
7-CF3
NHgluH
59q
Ph
H
NHgluH
59r
2-Th
H
NHgluH
59s
CONHgluH
H
NHgluH
59t
COOH
7-CF3
NHgluH
59v
CONHgluH
7-CF3
NHgluHTable 10
-
log
⁡
GI
50, -log⁡TGI, and -log⁡LC50 mean graph midpoints (MG-MID)a of in vitro inhibitory activity against human tumor cell linesb.
Compounds
-
log
⁡
GI
50 = μM
-
log
⁡
TGI = μM
-
log
⁡
LC
50 = μM
59c
4.14 = 72.44
4.02 = 95.49
4.00 = 100
59f
4.10 = 79.43
4.01 = 97.72
4.00 = 100
59g
4.22 = 60.25
4.01 = 97.72
4.00 = 100
59h
4.26 = 54.95
4.01 = 97.72
4.00 = 100
59i
4.20 = 63.09
4.00 = 100
4.00 = 100
59m
4.13 = 74.13
4.00 = 100
4.00 = 100
59n
4.63 = 23.44
4.15 = 70.79
4.02 = 95.49Figure 24
Chemical structure of compound59a–v.There are many quinoxaline derivatives which showed antitumor activity; Corona et al. [60] showed that 5,7-diamino-3-phenyl-2-[(3,5-dimethoxy)phenoxy]quinoxaline 60 has an antitumor activity in vitro, towards several types of tumors. Also the 3-(4-bromophenyl)-2-(ethylsulfonyl)-6 methylquinoxaline-1,4-dioxide 61 (Figure 25), has an activity against the tumor in the hypoxia stage, which is a phase where the tumor shows a resistance during chemotherapy and radiotherapy [61].Figure 25
Chemical structures of compounds60 and 61.Other compounds, derivatives of quinoxalinone, were submitted to a primary screening for anticancer activity following the known in vitro disease-oriented antitumor screening program, against a panel of about 60 human tumor cell lines [21]. The activity of each compound tested was deduced from a dose-response curve according to the data provided by NCI while compound 62 (Figure 26) was found to have encouraging in vitro anticancer activity at a concentration of 10–4 M.Figure 26
Chemical structure of compound62.Fourteen out of 21 quinoxaline derivatives described by Piras et al.’s [62] present paper were selected at NCI for evaluation of their in vitro anticancer activity. Preliminary screening showed that some derivatives exhibited a moderate to strong growth inhibition activity on various tumor panel cell lines between 10–5 and 104 M concentrations. Interesting selectivities were also recorded between 10–8 and 10–6 M for the compounds 63 and 64 (Figure 27).Figure 27
Chemical structures of compounds tested.Based on screening hit 1, a series of tricyclic quinoxalinones65–71 (Figure 28) has been designed and evaluated for inhibition of PARP-1 [63]. Substitutions at the 7- and 8-positions of the quinoxalinone ring led to a number of compounds with good enzymatic and cellular potency. The tricyclic quinoxalinone class is sensitive to modifications of both the amine substituent and the tricyclic core.Figure 28
Chemical structures of compounds65–71.The antitumor activity of synthesized quinoxalines72–77 (Figure 29) has been evaluated by studying their possible inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). Said compounds demonstrated strong inhibitory effects on the EBV-EA activation without showing any cytotoxicity and their effects being stronger than that of a representative control, oleanolic acid. Furthermore, compound 72 exhibited a remarkable inhibitory effect on skin tumor promotion in an in vivo two-stage mouse skin carcinogenesis test using 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promoter [64].Figure 29
Chemical structure of compound72–77.A series of ruthenium(II) arene complexes with 3-(1H-benzimidazol-2-yl)-1H-quinoxalin-2-one78 (Figure 30), bearing pharmacophoric groups of known protein kinase inhibitors, related benzoxazole and benzothiazole derevatives have been synthtised, therefore antiproliferative activity in three human cancer cell lines (A549, CH1, and SW480) was determined by MTT assays, yielding IC50 values of 6–60 μM for three unsubstituted metal-free ligands, whereas values for the metal complexes vary in a broad range from 0.3 to 140 μM. Complexation with osmium of quinoxalinone derivatives results in a more consistent increase in cytotoxicity than complexation with ruthenium [65].Figure 30
Chemical structure of compound78.Deregulation of cellcycle control is a hallmark of cancer. Thus, cyclin-dependent kinases (Cdks) are an attractive target for the development of anticancer drugs. Rübsamen-Waigmann et al. [28] report the biological characterization of a highly potent pan-Cdk inhibitor with a macrocycle-quinoxalinone structure. Compound 79 (Figure 31) inhibited Cdk1, 2, 4, 5, 6, and 9 with equal potency in the nM range and was selective against kinases other than Cdks. This compound inhibited multiple events in the cell cycle in vitro, including retinoblastoma protein (pRb) phosphorylation, E2F-dependent transcription, DNA replication (determined by bromodeoxyuridine incorporation), and mitosis completion (assayed by flow cytometry) in the 10 nM range (Table 11).Table 11
Enzyme inhibition activity of compound 79 against the Cdk family and other kinases.
Kinases
IC50 (nM)
Selectivity (fold)
Cdk4
4.1
1.0
Cdk6
12
Cdk2
3.4
Cdk1
1.0
Cdk5
4.5
Cdk7
660
PKA
>730
PKC
230
ERK1
>730
ERK2
>730
P38α
>2400
KDR
250
Flt-1
330
Flt-4
71
FGFR1
2000
FGFR2
610
Src
260
Tle-2
>4900
PDGFβ
480
EGFR
>2400Figure 31
Chemical structure of compound79.Moreover, this compound induced cell death, as determined by induction of the subG1 fraction, activated caspase-3, and an exin V. In vivo, compound79 showed antitumor efficacy at a tolerated dose. In a nude rat xenograft tumor model, an 8 h constant infusion of compound 79 inhibited pRb phosphorylation and induced apoptosis in tumor cells at 30 nM, which led to the inhibition of tumor growth. Immunosuppression was the only liability observed at this dose, but immune function returned to normal after 10 days. Suppression of pRb phosphorylation in tumor cells was clearly correlated with tumor cell growth inhibition and cell death in vitro and in vivo. In vivo, compound M inhibited pRb phosphorylation in both tumor and gut crypt cells. Rb phosphorylation may be a suitable pharmacodynamic biomarker in both tumors and normal tissues for monitoring target engagement and predicting the efficacy of compound 79 [66].The KRAS oncogene is found in up to 30% of all human tumors. In 2009, RNAi experiments revealed that lowering mRNA levels of a transcript encoding the serine/threonine kinase STK33 was selectively toxic to KRAS-dependent cancer cell lines, suggesting that small-molecule inhibitors of STK33 might selectively target KRAS-dependent cancers. To test this hypothesis [67], we initiated a high-throughput screen using compounds in the Molecular Libraries Small Molecule Repository (MLSMR). Several hits were identified, and one of these, a quinoxalinone derivative, was optimized. Extensive SAR studies were performed and led to the chemical probe 53 that showed low nanomolar inhibition of purified recombinant STK33 and a distinct selectivity profile as compared to other STK33 inhibitors that were reported in the course of these studies. Even at the highest concentration tested (10 μM), 80 (Figure 32) had no effect on the viability of KRAS-dependent cancer cells. These results are consistent with other recent reports using small-molecule STK33 inhibitors. Small molecules having different chemical structures and kinase-selectivity profiles are needed to fully understand the role of STK33 in KRAS-dependent cancers. In this regard, 80 is a valuable addition to small-molecule probes of STK33.Figure 32
Chemical structure of compound80.P-glycoprotein-mediated drug efflux from cells is believed to be an important mechanism in multidrug resistance (MDR) in cancer chemotherapy. The identification and development of P-glycoprotein inhibitors with high potency and low cytotoxicity hold great promise for overcoming MDR. A series of quinoxalinone derivatives was synthesized and evaluated primarily for their antiproliferative effect and MDR reversal activity in in vitro assay systems [56]. Biological assays demonstrated that the compounds 81a–t (Figure 33 and Table 12) were, in general, endowed with good activity as P-glycoprotein inhibitors. Among them, compounds which showed the highest MDR reversal activity without significant cytotoxicity displayed potent P-glycoprotein inhibition activities and may be worthy of further research as potential adjunctive agents for tumor chemotherapy [68].Table 12
List of compounds tested.
Compound
R1
R2
Compound
R1
R2
81a
H
81l
H
81b
H
81m
H
81c
H
81n
H
81d
H
81o
H
81e
H
81p
F
81f
H
81q
OCH3
81j
F
81r
H
81k
OCH3
81s
H
81t
HFigure 33
Chemical structure of compounds81a–t.


## 7. Receptor Antagonist Activity

A series of quinoxalinones was synthesized as antagonists of bradykinin, which is a peptide responsible for the dilatation of blood vessels, thus leading to the lowering of blood pressure [69].Bayoumi et al. [70] showed that 1,2,4-triazolo(4,3-a)quinoxalin-4-5H-one derivatives 82 and 83 (Figure 34) act as AMPA receptor antagonists.Figure 34
Chemical structures of compounds tested.


## 8. Antithrombotic Activity

Excessive uncontrolled activation of the hemostatic system results in thromboembolic diseases, a major cause of morbidity and mortality in our society. The central role of the serine proteases factor Xa and thrombin in hemostasis make them attractive targets for antithrombotic therapy. Factor Xa, factor Va, calciums and phospholipids form the prothrombinase complex, which converts prothrombin into thrombin. Thrombin very efficiently initiates fibrin formation, platelet aggregation, and activation of factors V and VIII. Selective inhibitors of thrombin and factor Xa are expected to be therapeutically useful in the treatment or prophylaxis of thromboembolic diseases [71–73].In order to design and develop orally active coagulation inhibitors containing heterocyclic core structures, Ries et al. [74] identified some compounds as potent thrombin inhibitors 2 in vitro.Based on this lead structure novel coagulation inhibitors having quinoxalinone84 (Figure 35) as the central template have been designed. These compounds inhibited thrombin and factor Xa in the nanomolar range.Figure 35
Chemical strucure of compound84.


## 9. Antidiabetic Activity

Diabetes is a serious metabolic disorder with micro- and macrovascular complications which causes significant morbidity and mortality. In the developing world, the diabetes epidemic is accelerating with an increased proportion of affected people in the younger population.Recently, some reports described that type 2 diabetes was being diagnosed even in children and adolescents [75]. The latest WHO Global Burden of Disease estimate the worldwide burden of diabetes in adults to be around 173 million in the year 2002 [76] and around two-thirds of these live in developing countries. So, nowadays, it has become a growing public health concern worldwide causing severe and costly complications including blindness cardiac and kidney diseases [77]. Current therapies do little in preventing complications although they provide good glycemic control.Besides this, these drugs are also associated with side effects. Thus, it is necessary to continue research for new and, if possible, more efficacious drugs, particularly bioactive quinoxalinone-based compounds, which are effective in the treatment of diabetes and its complications. Through this procedure, a new class of quinoxalinone-based aldose reductase inhibitors were synthesized successfully85. Most of the inhibitors, with an N1-acetic acid head group and a substituted C3-phenoxy side chain, proved to be potent and selective. Their IC50 values ranged from 11.4 to 74.8 nM. Among them, 2-(3-(4-bromophenoxy)-7-fluoro-2-oxoquinoxalin-1(2H)-yl)acetic acid 57 and 2-(6-bromo-3-(4-bromophenoxy)-2-oxoquinoxalin-1(2H)-yl)acetic acid were the most active 86 [78] (Figure 36).Figure 36
Chemical strucure of compounds tested.To conclude this review of biological activity of the quinoxalinone derivatives, we will mention that the compounds87–89 (Figure 37) are considered as a novel potential therapeutic avenue for autism [79]; it is pharmacophore models are a promising milestone to a class of SSRIs with dual action.Figure 37
Chemical structures of compounds87–89.Finally, a series of new quinoxaline derivatives90 (Figure 38), which could act as modulators of the AMPA receptor mediators of synaptic responses, has been synthetized [80].Figure 38
Chemical structure of compound90.The circle containing nitrogen designates a heterocycle of 5 to 8 rings, and the group R′ may be a group 2- or 3-alkyl, cycloalkyl, hydroxy, alkoxy, alkoxy-alkyl, hydroxy-alkyl, or carbamoyl.


## 10. Conclusion

In recent years, the quinoxalinone made a tremendous achievement in the biological and pharmacological fields. Also, the modifications in the basic structure of the quinoxalin-2-one have enabled the emergence of new derivatives with a wide spectrum of biological activities.In conclusion a wide variety of biological activities of quinoxalinone have been described. Quinoxaline moiety containing 1,4-di-N oxide shows broad spectrum of activity against wide number of bacterial species and also exhibited cytotoxic activity. Those drugs containing quinoxaline moiety are Carbadox and Brimonidine. Carbadox, a well-known synthetic antibacterial agent used for treatment of various bacterial diseases, and Brimonidines showed the importance of quinoxalines as a pharmaceutical agent as it palliates the symptoms of glaucoma through reducing intraocular pressure.Studies of these derivatives have shown that structural modification can improve its pharmacological profile conferring antibacterial, anticancer, anti-HIV, antidiabetic, and anti-inflammatory properties.



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