Review Articles

2018  |  Vol: 4(2)  |  Issue: 4(March-April)  |
Hydrazones as potential anticancer agents: An update

Diksha Saini, Monika Gupta*

Department of Pharmaceutical Chemistry, A.S.B.A.S.J.S.M. College of Pharmacy, Bela, 140111(Punjab), India

*Corresponding author

Dr. Monika Gupta

Department of Pharmaceutical Chemistry, A.S.B.A.S.J.S.M. College of Pharmacy, Bela, 140111 (Punjab), India


Hydrazone derivatives of carbonyl compounds considered to be biologically important class of compounds.  Literature studies revealed that hydrazones and various substituted hydrazones are associated with a broad spectrum of biological activities such as antioxidant, antibacterial, antiviral, analgesic, antiplatelet, antimicrobial, and anticancer.  The present paper is focused on the overview of the literature findings of the last four years (2014–2017) covering the research on anticancer activity of hydrazone derivatives.

Keywords: Hydrazones, cytotoxicity, Anti proliferative, tubulin polymerization


The hydrocarbons with the structure R1R2C=NNH2 are categorized as Hydrazones (March, 1985). They contain NNH2 functional group in place of carbonyl oxygen of ketones and aldehydes. They are formed usually by the action of ketones or aldehydes on hydrazine (Stork and Benaim, 1977; Day and Whiting, 1970) (Figure 1). The hydrazones contain C = N bond, which is conjugated with a lone pair of electrons of the nitrogen atom. The carbon atom of the hydrazones has both electrophilic and nucleophilic nature while nitrogen atoms are nucleophilic in nature. The α-hydrogen of hydrazones is more acidic than that of acidic ketones. The combination of hydrazones with other functional group leads to compounds with unique physical and chemical character so they are considered important for the synthesis of heterocyclic compounds. 

Figure 1. Reaction for formation of hydrazone            

Hydrazones act as precursor for the synthesis of different heterocyclic scaffolds (Rollas and Kucukguzel, 2007), like 1,3,4-oxadiazolines (Dogan et al., 1998), azetidin-2-ones (Kalsi, et al., 2006), coumarins (Mohareb, et al., 2011), 1,3-thiazolidin-4-ones (Popiolek, et al., 2015; Popiolek, et al., 2016),  and 1,3-ben- zothiazin-4-ones (Popiolek, 2016).  

The hydrazones exhibit geometrical isomerism (syn and anti) due to the presence of the double bond between C and N. This geometrical isomerism have been reported to play important role in the bioactivity of the acyl hydrazones hence their studies are very crucial to develop synthetic methods for selective synthesis of a particular isomer. The hydrazones have been reported to possess diverse biological activities such as anti-inflammatory, analgesic, anticonvulsant, antituberculosis, antitumor, anti-HIV and antimicrobial activity.

Recent years has witnessed some of the marketed hydrazone derivatives such as Iproniazide (Singh, et al., 1992) as antidepressant; Nifuroxazide and Furazolidone (Chatterjee, et al., 1979) an oral antibiotic; used in colitis and enteritis treatment respectively, Nitrofurazone (Mccalla, et al., 1970) in the treatment of skin infections due to skin grafts and Nitrofurantoin (Munoz-Davila, 2014) in urinary tract infections. 2,4-Dinitrophenyl hydrazones of diaryl ketones named 4,4'-Dihydrobenzophenone-2,4-dinitrophenyl-hydrazone (A-007) (Shankar et al., 2017) have been reported in phase II clinical trials. Small molecules like guanylhydrazone (Shankar et al., 2017) have been reported to block estrogen receptor (ER) activity by directly interfering with coactivator binding to agonist-liganded ER.

The present review emphasizes on the anticancer activity of hydrazone derivatives reported in last four years.

Anticancer activity of Hydrazones

Cancer can be defined as a disease in which a group of abnormal cells grow uncontrollably by disregarding the normal rules of cell division. Normal cells are constantly subjected to signals that dictate whether the cell should divide, differentiate into another cell or die. Cancer cells develop a degree of autonomy from these signals, resulting in uncontrolled growth and proliferation. Anticancer agents act on various tumour cells by different mechanisms such as they act by inhibiting protein kinases, cause microtubule dysfunctioning, inhibiting topoisomerase I or II, down regulating oncogenes expression, induce apoptosis and interrupt cell division. Researchers synthesized various substituted hydrazones and screened for their anticancer activity on various cell lines i.e. human breast cancer, human colon carcinoma, leukemia, lung cancer, human gastric cancer, human esophageal cancer and pancreatic cancer during last five years.  They have been reported to act by inhibiting RNA and DNA synthesis (Kaplanek et al., 2015), inhibiting mitosis (Kaplanek et al., 2015), induced caspase-dependent apoptosis (Tantak et al., 2017), inhibiting tubulin polymerization and cause cell cycle arrests in G2/M phase (Tantak et al., 2017), cancer cycle arrest at sub G1/G0 phase (Senkardes et al., 2016), tumor cell apoptosis (Shen et al., 2017).

Tantak et al. (2017) designed and synthesized bis(indolyl)ketohydrazide-hydrazonescompounds (Tantak et al., 2017) (Figure 2) and evaluated them against multiple cancer cell lines. Among the twenty synthesized compounds, compounds 1a, 1b, 1c, 1d, 1e exhibited anticancer activity. SAR studies revealed that C-5 methoxy, bromo and N-(4-chlorobenzyl) groups in indole ring are beneficial for the activity Compound 1e [N'-((1H-Indol-3-yl)methylene)-2-(1-(4-chlorobenzyl)-1H-indol-3-yl)-2-oxoaceto-hydrazide] contains two indole rings present which are critical for the excellent in vitro anticancer activity and were found to be the most active against various cell lines, human breast cell lines (MCF-7, MDA-MB-231), human colon carcinoma cell lines (HCT-116) and leukemia cell line (JURKAT). It was also found to be more selectively cytotoxic against tumor cells when compared to normal cells. Mechanism of action studies done by researchers indicated that active compound induced caspase-dependent apoptosis in cells. It arrests cell cycle in G2/M phase by inhibiting of tubulin polymerization.

Figure 2. Bis(indolyl)ketohydrazide-hydrazones



Shen et al. (2017) synthesized complex (E)-N'-(1-(pyridin-2-yl)ethylidene) nicotinohydrazide (penh) and metals complex such as [Co (penh)2], [Cu(penh)2], [Cd(penh)2], [Mn(penh)2] (Shen et al, 2017). All  complexes were able to markedly decrease the proliferation rate of various types of tumor cell, including the human lung cancer cell line A549, human gastric cancer cell line BGC823 and human esophageal cancer cell line Eca109, in a concentration-dependent manner. Furthermore, the complexes promoted tumor cell apoptosis.

The anticancer activity of water soluble methoxy polyethylene glycol (mPEG) derivatives of tocotrienol (T3) isomers of vitamin E was previously found to be reduced when compared to the parent free isomers. This could be due to the ester bond formation between the mPEG and the 6-OH group on the chroman moiety of the T3 isomer. To further investigate Fayyad et al. (2017) synthesized, physiochemical characterized, stable amide and hydrazone conjugates between mPEG and carbon-5 on the chroman moiety of T3(Fayyad et al., 2017) (Figure 3) and examined the cytotoxicity of the newly synthesized mPEG conjugates against breast (MCF-7 and MDA- MB-231) and pancreatic (BxPC-3 and PANC-1) cancer cells. Conjugates were synthesized by direct conjugation of succinyl chloride derivatives of mPEG to the α-tocopherol and γ-tocotrienol isomers of vitamin E. The hydrolysis of the hydrazone conjugate was pH dependent with highest release at acidic (pH 5.5) conditions, whereas the amide conjugate was stable in all tested media. The amide conjugate nonetheless showed greater cytotoxicity than the hydrazone conjugate, which suggested that maintaining solubility and the presence of free 6-OH group are important for γ-T3 to exert anticancer activity in vitro.

Figure 3. γ-T3-mPEG 2000 hydrazone (n= 48 mPEG 2000)

In another study a series of ten novel Hydrazide–hydrazones linked indole and indazole moieties were synthesized (Sreenivasulu et al, 2017) (Figure 4) and evaluated for their cytotoxicity against four human cancer cell lines i.e. HeLa (cervical cancer cells), MDA-MB-231, MCF-7 (human breast adenocarcinoma cells) and A549 (human alveolar adenocarcinoma cells). The  docking studies performed by suggested that the presence of the indole ring plays a critical role in the cytotoxicity of the compounds. Three of the synthesized compounds 2a, 2b, and 2c showed a comparatively promising cytotoxicity on different cell lines. Compound 2b showed promising cytotoxic effect on HeLa and A549 cancer cell lines. The compound 2c showed promising cytotoxic effect on MCF-7 cancer cell lines. While, compound 2a showed a promising cytotoxic effect on A549 and HeLa cancer cell lines with. Further, compounds 3a and 3b showed promising cytotoxicity towards MCF cell line.

Figure 4. Hydrazide–hydrazones linked indole and indazole moieties





Kaplancikli et al. (2017) synthesized Thiazolyl hydrazone (Kaplancikli et al., 2017) (Figure 5) from the reaction of 1-(4-Phenylcyclohexylidene)thiosemicarbazide with 2-Bromoacetophenone derivatives and evaluated for  their anticancer activity on A549 human lung adenocarcinoma, HepG2 human liver hepatocellular carcinoma and C6 rat glioma cell lines. Compound 4a [4-(4-Methylsulfonylphenyl)-2-(2-(4-phenylcyclohexylidene)hydrazinyl)thiazole] was found to be the most promising anticancer agent against HepG2 cell line. Compounds 4b and 4c also exhibited cytotoxic effects on HepG2 cell line.

Figure 5. Thiazolyl hydrazone



Figure 6. Triaryl-substituted hydrazones





Shankar et al. (2017) designed and synthesized a series of triaryl-substituted hydrazones (Shankar et al., 2017) (Figure 6) and screened for anti-proliferative activity against breast and uterine cancer cell lines. Two compounds 5a and 5b were found to be the most active, 5a showed the maximum inhibition of both functional estrogen receptor containing Michigan cancer foundation-7 cells and Ishikawa cells by its estrogen receptor antagonistic effect. Compound 5b was selectively most active against ER-negative MD Anderson metastatic breast-231 cells.

Figure 7. 2',4'-Difluoro-4-hydroxy-N'-[(pyridin-2-yl)methylidene]biphenyl-3-carbohydrazide


Figure 8. 2-(1-(2-(3-Phenyl-5-(phenylthio)-3H-[1,2,3]triazolo[4,5-d]pyrimidin-7-yl)hydrazono)ethyl)phenol


Senkardes et al.(2016)  designed and synthesized a number of 2',4'-Difluoro-4-hydroxy-N'-(arylmethylidene) biphenyl-3-carbohydrazide (Senkardes et al., 2016) (Figure 7) as anti-HCV and anticancer agents. Compound 2',4'-Difluoro-4-hydroxy-N'-[(pyridin-2-yl)methylidene]biphenyl-3-carbohydrazide (6a) with 2-pyridinyl group in the hydrazone part exhibited promising cytotoxic activity against liver cell lines i.e. Huh7, HepG2, Hep3B, Mahlavu, FOCUS and SNU-475cells, respectively, and produced dramatic cell cycle arrest at SubG1/G0 phase as an indicator of apoptotic cell death induction.  

Li et al. (2016) designed and synthesized a series of [1,2,3]Triazolo[4,5-d]pyrimidine derivatives bearing a hydrazone moiety (Li et al., 2016) (Figure 8) and biologically evaluated for their antiproliferative activity. Among all the synthesized compounds, compound 7a exhibited more potent inhibition against the tested cancer cells such as MGC-803 (human gastric cancer cell line), MCF-7 (human breast cancer cell line) and EC-109 (human esophageal cancer cell line) by inducing apoptosis. Mechanism investigation showed that compound 7a can inhibit the colony formation and induce morphological changes and lead to apoptosis with the decrease of mitochondrial membrane potential in MGC-803 cells.

Figure 9. Morpholinothiophene hydrazone derivatives





Figure 10. Caffeine- hydrazone



Taha et al. (2016) synthesized a series of Morpholine derivatives (Taha et al., 2016) (Figure 9). Small series of  morpholinothiophene hydrazones were synthesized by treating 5-Morpholinothiophene-2-carbaldehyde with different Aryl hydrazides and evaluated for their in vitro anticancer potential against two human cell lines like MCF-7 (breast carcinoma) and HepG2 (liver carcinoma). The results showed morpholine derivatives showed strong growth inhibitory effect on MCF-7 cell by encouraging cancer cell apoptosis. Compounds 8a and 8b were found to be outstanding inhibitors for MCF-7 cell. Compound 8c showed potent inhibition against HepG2 cell. The molecular docking studies were performed to understand the binding interaction of the active compounds.

Some novel anticancer agents based on Caffeine-hydrazones bearing 2-hydroxyaryl or 2-N-heteroaryl moiety were also synthesized (Kaplanek et al., 2015) (Figure 10). Anticancer activity evaluation done by using nine cell lines, seven were cancer cell lines and two were non-malignant cell lines. Six compounds (9a, 9b, 9c, 9d, 9e and 9f) show high cytotoxic activity. The best results were obtained for compounds possessed 2-N-heterocyclic moiety (9c, 9d and 9e) which show superior selectivity against malignant versus non-malignant cells. Majority of tested compounds exhibits dose dependent inhibition of both RNA and DNA synthesis, mitosis and induced apoptosis.

Figure 11.  Hydrazone derivatives based on a Troger's base skeleton



Another hydrazone derivatives based on a Troger’s base skeleton were synthesized (Kaplanek et al., 2015) (Figure 11) and biologically evaluated against anticancer and antimicrobial activity. The anticancer activity of the prepared hydrazones was tested on nine cell lines. Compounds 10a, 10b, 10c, 10d and 10e showed excellent selectivity against leukaemic cells. Compounds 10b, 10c and 10e showed superior selectivity for all leukaemic and cancer cell lines compared to healthy cell lines. The prepared compounds did not show any antimicrobial activity. Complexation studies with biologically important metal ions demonstrated that these compounds could bind to the Co2+, Cu2+, Fe3+, Ni2+ and Zn2+ ions. DNA interaction studies showed that the compounds do not interact with DNA alone, but their metallocomplexes with Co2+, Cu2+, Fe3+, Ni2+ and Zn2+ interact, probably through intercalation into DNA. Results demonstrate that hydrazones with Troger’s base skeletons are a promising class of potent cytostatic agents with high selectivity toward leukaemia and cancer cells.

Figure 12. 6-Brominated coumarin hydrazide-hydrazone


Nasar et al. (2014) designed and synthesized sixteen Coumarins bearing hydrazide-hydrazone moiety (Nasar et al., 2014) (Figure 12) and evaluated them against human drug-resistant pancreatic carcinoma (Panc-1) cells and drug-sensitive (hepatic carcinoma; Hep-G2 and leukemia; CCRF) cell lines in vitro. The most potent compounds were 6-brominated coumarin hydrazide-hydrazone derivatives BCHHD’s 11a, 11b and 11c. BCHHD 10a showed significant cytotoxicity against all tested cells, whereas BCHHD’s 11b and 11c showed significant antiproliferative activity only against resistant Panc-1cells. All the BCHHD’s were able to activate caspases 3/7 and they could induce apoptosis in resistant Panc-1 cells. The microarray result showed that BCHHD 11a induced the expression of apoptosis and cell cycle arrest in G2/M phase.  Moreover, BCHHD 11a induced the up-regulation of CDKN1A, DDIT4, GDF-15 and down-regulation of CDC2, CDC20, CDK2 genes. 11a could be a potent anticancer drug to overcome drug resistance in cancer and it could be highly beneficial for patients in the clinic. 

Figure 13. Cu(II) complexes of hydrazone ligand containing triphenylphosphonium moiety


Chew et al. (2014) synthesized Mononuclear Cu(II) complexes of hydrazone ligand containing triphenylphosphonium moiety (Chew et al., 2014) (Figure 13). The cytotoxicity and topoisomerase I (topo I) inhibition activities of these compounds were studied. Complex 12 i.e. (1,10’-phenanthroline)[5-(triphenylphosphoniummethyl)-salicylaldehydebenzoylhydrazonato] copper(II) monohydrate ethanol exhibits the highest activity against human prostate adenocarcinoma cell line (PC-3) with the IC50 value of 3.2 mM. The addition of N,N-ligands to the copper(II) complex lead to the enhancement in the cytotoxicity of the compounds, especially against human prostate adenocarcinoma cell line. All the compounds can inhibit topo I upon complexation through the binding to DNA and the enzyme.


The present work gives an overview of the anticancer activity of diverse hydrazone derivatives. The hydrazone moiety has been an indispensable pharmacophore for various bioactive molecules. During last five years, hydrazones have occupied a significant position in anticancer research by exhibiting variety of mechanism of action and possessing in vitro growth inhibition activity against various cancer cell lines. This work can act as an aid to the researchers for the development of novel anti cancer hydrazones. Based upon the reported pharmcophores; the scientific community can utilize hydrazones as lead and explore further to get safer and effective compounds.

Conflict of interest

The authors confirm that this article content has no conflicts of interest.


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