Free Radical Scavenging and Cytotoxic Activities of Substituted Pyrimidines
Qurat-ul-Ain, Shafqat Hussain, M. Iqbal Coudhary, Khalid Mohammed Khan
FFree Radical Scavenging and Cytotoxic Activities of Substituted Pyrimidines
Qurat-ul-Ain, Shafqat Hussain, M. Iqbal Coudhary, and Khalid Mohammed Khan Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah-21589, Saudi Arabia Department of Clinical Pharmacy, Institute for Research and Medical Consultations (IRMC), Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam, 31441, Saudi Arabia [email protected] Summary:
A library of substituted pyrimidines was synthesized and evaluated for free radical scavenging, and in vitro cytotoxic activity in 3T3 cells. All compounds showed good free radical scavenging activity with IC values in the range of 42.9 ± 0.31 to 438.3 ± 3.3 µ M as compared to the standard butylated hydroxytoluene having IC value of 128.83 ± 2. 1 µ M. The structure activity-relationship was also established. Selected analogues , , , , , , , , , , , , , , , , , and were tested for cytotoxicity in mouse fibroblast 3T3 cell line using MTT assay, and most of the analogues showed cytotoxicity. This study has identified a number of cytotoxic novel substituted pyrimidines having free radical scavenging activities that can be used as inhibitory compounds for those cancer cells whose growth is mediated by reactive oxygen species. Keywords:
Pyrimidine nucleotide, synthesis, free radical scavenging, SAR, cytotoxicity
Introduction:
Scavenging of free radicals by antioxidant compounds is an important biological function that may maintain in the body a low oxidative damage. Antioxidant compounds of different synthetic, and natural sources can scavenge these free radicals with the formation of less reactive species, and thus diminish the radical induced oxidative damage that is possibly associated with many diseases, including cancers.
Numerous classes of synthetic compounds have been screened to reveal their free radical scavenging ability, including synthetically obtained deoxyribonucleic acids (DNA) and nucleotide analogues like pyrimidine derivatives.
These pyrimidines, present in numerous pharmaceutically important compounds, have been known to prevent cancer cell proliferation. Substituted pyrimidine primarily display their anticancer activity through intercalating with DNA nucleotide bases. However, they may prevent ROS induced DNA mutations in a way similar to other anticancer and antiviral molecules.
In recent years, anticancer drugs already being used in medical practice or being tested in clinical studies have been often based on pyrimidine skeleton, and new pyrimidine derivatives continue to show promising activities.
However, synthesis f antioxidant molecules can be a new approach to prevent proliferation of tumors whose growth is mediated by oxygen species. Besides their anti- tumor action, pyrimidine derivatives have also been found to possess additional biological activities including antibacterial, anti-folate, antibiotic, anti-HIV, anti-fungal, anti-mycobacterial, anti-leismanial were also found to inhibit tumor necrotic factor alpha (TNF-α) production. Herein, we report the free radical scavenging activities of a new library of pyrimidine derivatives to evaluate their potential against free radical sustained cancer cell proliferation. In the past, a number of pyrimidines were also found to inhibit enzymes such as tyrosine kinases, urease, β -glucuronidase, and cholinesterase. Furthermore, many pyrimidine analogues were found to exhibit inhibitory or modulatory activities in a number of biological situations.
19, 20
Therefore, we screen these synthetic pyrimidine derivatives for their in vitro free radical scavenging activity as well as to establish their cytotoxicity in a 3T3 mouse fibroblast cell line.
Scheme 1. Basic Skeleton of Pyrimidines.
Experimental
Material and Methods
All substituted pyrimidines were obtained from the in-house Molecular Bank facility of the Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Pakistan. DPPH was purchased from Sigma Aldrich (Germany). Ethanol and dimethyl sulfoxide (DMSO) (reagent grade) were purchased from Sigma Aldrich (USA). Standard compounds , i.e., butylated hydroxytoluene was purchased from Sigma Aldrich (Germany).
DPPH Radical Scavenging Assay
The Kumari Madhu method of DPPH (2,2-diphenyl-1-picryl-hydrazyl) assay was used to measure the free radical scavenging activity with small variations. This assay is based on the reduction of DPPH radical (violet colour) by free radical scavenger with a change of colour to pale yellow. The intensity of colour conversion is directly related to the potency of free radical scavenging compounds, and to the extent of reduction in absorbance. In the visible region, absorbance reduction can be measure at 517 nm. Compounds solutions of (0.5 mM) in DMSO were prepared. Two-fold dilution method was used to dilute compounds solutions to different concentrations. 5 µl sample of each concentration was transferred to 96 wells plate in triplet, at 517 nm pre read was recorded. 95 µ l of 0.3 mM freshly prepared ethanolic solution of DPPH was added in each of the 96 wells. A final absorbance reading was taken at 517 nm. DMSO was used as negative control and butylated hydroxytoluene was used as the positive control. The radical scavenging activities were calculated by the following equation: % Radical scavenging activity of DPPH = [A -A /A ] ×100 Where: A : The absorbance of all reagents without the tested compounds. A : The absorbance in the presence of test compounds. TT Assay
The pyrimidine derivatives were tested by the method previously described by Dimas et al . to establish their cytotoxicities in a normal cell line. In 96-well plate, mouse fibroblast 3T3- cells (2 ×10 cells/ mL) were grown over night in DMEM medium along with 10% FBS, pen/ strep (100 units/ mL), supplemented with 5% CO at 37 º C. After 24 h, the old media was discarded, cells were treated with different concentrations of the tested compound, and further incubated for 24 h. After 24 h, cells were washed, and the plate was again incubated with MTT solution for 4 h after which dimethyl sulfoxide 100uL added for 15 min to dissolved formazan crystals at room temperature. Finally, a micro plate reader (SpectraMax Plus-384) was used to record the absorbance at 540 nm. The IC was calculated and defined as the drug concentration ( µ M) causing cytotoxicity in 50%. cells.
Results and Discussion
Free Radical Scavenging Activity
The synthetic pyrimidine derivatives - were tested for their free radical scavenging, and cell cytotoxic potential. All compounds showed various degrees of radical scavenging activity inDPPH radical scavenging assay, and their IC values ranged between 42.9 ± 0.31 to 438.3 ± 3.3 μ M. Derivatives , , , , , , and with IC values of 55.6 ± 2.1, 122.4 ± 1. 9, 107.65 ± 1.3, 108.4 ± 2.8, 113.4 ± 1.3, 42.9 ± 0.31, and 65.7± 1.80 µ M, respectively, showed free radical inhibitory activity that is many folds better than the standard butylated hydroxytoluene with IC value of 128.83 ± 2.1 µ M, as depicted in Figs. A-D, and Table-1. Compounds , , , , , and showed good to moderate activities (Fig. A-C and Table-1). The remaining derivatives, including , , , , , , , , and showed weak inhibitory activities (Fig. A-D and Table-1). Derivatives , , , , , were decleared as inactive derivatives of this series. Table-1:
Free radical scavenging activity of compounds ( ). Cpds IUPC Names R IC50 ± SEM a ( μ M)
1 5-(4-Hydroxy-3,5-dimethoxybenzylidene)-2-thioxodihydropyrimidine-4,6(1 H ,5 H )-dione 55.6 ± 2.1 2 5-(2-Bromo-4,5-dimethoxybenzylidene)-2-thioxodihydropyrimidine-4,6(1 H ,5 H )-dione 198.2 ± 4.5 3 5-((2-Hydroxynaphthalen-1-yl)methylene)-2-thioxodihydropyrimidine-4,6(1 H ,5 H )-dione 122.4 ± 1.9 4 5-(Thiophen-2-ylmethylene)-2-thioxodihydropyrimidine-4,6(1 H ,5 H )-dione NA 5 2-Thioxo-5-(3,4,5-trimethoxybenzylidene)dihydropyrimidine-4,6(1 H ,5 H )-dione 132.6 ± 1.2 5-(4-(Methylthio)benzylidene)-2-thioxodihydropyrimidine-4,6(1 H ,5 H )-dione 209 ± 4.4 7 5-((6-Bromo-4-chloro-2-oxo-2 H -chromen-3-yl)methylene)-2-thioxodihydropyrimidine-4,6(1 H ,5 H )-dione 322.4 ± 1.9 8 5-(Pyridin-4-ylmethylene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 179.7 ± 6.2 9 5-((6-Methylpyridin-2-yl)methylene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 211.2 ± 4.6 10 5-(4-Bromo-2,5-dimethoxybenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 204.5 ± 3.5 11 5-(3-Hydroxy-4-methoxybenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 107.65 ± 1.3 12 5-(3,4-Dimethoxybenzylidene)-2-thioxodihydrop 170.4 ± 2.5 yrimidine-4,6 (1 H ,5 H )-dione 13 5-(4-Hydroxy-3-iodo-5-methoxybenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 108.4 ± 2.8 14 5-(Anthracen-9-ylmethylene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione NA 15 5-(2-Hydroxy-4-methoxybenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 284.2 ± 5.9 16 5-(2,4-Di-tert-butyl-3-chlorobenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione NA 17 5-(2-Aminobenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione NA 18 5,5'-(1,4-Phenylenebis(methanylylidene))bis(2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione) 113.4 ± 1.1 19 5-(3,5-Dibromo-4-hydroxybenzylidene)-2-thioxodihydrop 170.8 ± 1.4 rimidine-4,6 (1 H ,5 H )-dione 20 5-(4-(Dimethylamino)benzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione NA 21 5-(2-Methylbenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 438.3 ± 3.3 22 5-(4-Ethoxybenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 230.7 ± 2.6 23 5-(2,4-Dihydroxybenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 231.9 ± 6.9 24 5-(2-Hydroxy-3-methoxybenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 200.6 ± 1.8 25 5-((5-Methylfuran-2-yl)methylene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione NA 26 5-(3,4-Dihydroxybenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 42.9 ± 3.6 27 5-(2-Hydroxy-5-methoxybenzylidene)-2-thioxodihydropyrimidine-4,6 (1 H ,5 H )-dione 177.1 ± 3.6 28 2-Thioxo-5-(2,3,4-trihydroxybenzylidene)dihydropyrimidine-4,6(1 H ,5 H )-dione 65.7 ± 1.8 BHT b a SEM is the standard error of the mean, BHT b : Butylated hydroxytoulene Structure- Activity Relationship
A structure-activity relationship established for all compounds that confirmed substitution of various functionalities at the aromatic ring confers free radical scavenging activity to each particular pyrimidine analogue. Analogue , a 3,4-dihydroxybenzylidene was found to be the most active pyrimidine among the series, with an IC value of 42.9 ± 0.31 μ M, corresponding to 84.07% radical scavenging activity that is as good as 85.87% radical scavenging activity of the standard drug (Tables-1, and 3). The high activity shown by analogue is due to the positional change of dihydroxyl groups present an aromatic moiety (Table-1). Literature reports have also shown that the phenolic hydroxyl group is responsible for the antioxidant function. Compound is the second most potent derivative among the series, containing 4-hydroxy-3,5-dimethoxy groups with IC of value 55.6 ± 2.1 µ M, with corresponding 91.58% radical scavenging activity (Tables-1, and 3). With 74.69% radical scavenging activity derivative , ith three hydroxyl groups at 2,3, and 4-positions, was found to be the third most effective derivative of the series (Tables-1, and 3). The lesser activity shown by analogue as compared to compound might be due to the extra hydroxyl group which creates some steric hindrance (Table-1 and 3). In this study, we observed that all other hydroxyl group containing derivatives, such as , , , , , and also showed antioxidant activity. The lesser activity shown by analogue as compared to compound might be due to the extra hydroxyl group which creates some steric hindrance (Table-1 and 3). In this study, we observed that all other hydroxyl group containing derivatives, such as , , , , , and also showed antioxidant activity. The difference in their activity seems to be either due to the number, position, and presence of other substituents along with the hydroxyl group (Table-1). Compound , and have almost identical free radical scavenging activity with 74.3%, and 90.76 % (Table-3). The moderate activity of compound may be due to the lone pair of electrons on the pyridine nitrogen while in derivative , due to the presence of two methoxy groups (Table-1). Compound , and with (6-bromo-4-chloro-2-oxo-2 H -chromen-3-yl) and (6-bromo-4-chloro-2-oxo-2 H -chromen-3-yl) substitutions were found to be the least active of the series (Tables-1, and 3). The anthranyl analogue , di tert -butyl compound , derivative having aminobenzylidene, derivative with dimethylamino group, methylfuryl molecule , and thiophenyl derivative did not show any antioxidant activity. 4-Bromo-2,5-dimethoxy compound and 2-bromo-4,5-dimethoxy analogue have the same substituents but their positions are different, providing little difference in their activities (Table-1). By changing the substituent from p -thiomethyl, as in analogue , to an amino groups such as N , N -dimethyl amino derivative and methyl-2-pyridinyl molecule , it was observed the amino analogues showed greater radical scavenging activity than the one with p -thiomethyl and N , N -dimethyl amino functionalities. This might be due to the better ability of the former to provide free electrons (Tables-1, and 3). Cell Cytotoxic Activity
Cytotoxicity of compounds , , , , , , , , , , , , , , , , , and was carried out by using mouse fibroblast 3T3 cell line. Derivatives , , , , , , , , , , , , , and exhibited non-cytotoxicity in mouse fibroblast 3T3 cell line (Table-3). Derivatives and were found to have weak cytotoxic effect with IC values of 27.038 ± 0.26, and 22.4 ± 0.76, µ M, respectively. However, compound was found to be moderately cytotoxic with IC value of 19.482 ± 0.406 µ M, and only compound was found to be cytotoxic with IC value of 7.038 ± 0.26 µ M. Table-2:
Cytotoxicity studies of selected pyrimidine derivatives.
Compounds Cell Cytotoxicity IC ( µ M)± SEM Compounds Cell Cytotoxicity IC ( µ M) ± SEM
1 >30 >30 2 19.4 ± 0.4 >30 3 >30 >30 5 >30 >30 6 >30 >30 8 >30 >30 9 >30 >30 10 7.0 ± 0.2 >30 Cycloheximide 0.2± 0.1 >30 SEM: standard error mean, cycloheximide standard drug able-3: % RSA of selected derivative. % RSA: % Radical Scavenging Activity, Butylated hydroxytoulene (BHT) % RSA: 85.87 -20020 % R ad i c a l S c a v eng i ng A c t i v i t y Compounds500 uM 250 uM 125 uM62.5 uM 31.25 uM 15.62 uM A -2002040 % R ad i c a l S c a v eng i ng A c t i v i t y Compounds
500 uM 250 uM 125 uM B -20020406080
13 15 18 19 21 BHT % R ad i c a l S c a v eng i ng A c t i v i t y Compounds500 uM 250 uM 125 uM62.5 uM 31.25 uM 15.62 uM C -20 % R ad i c a l S c a v eng i ng A c t i v i t y Compounds500 uM 250 uM 125 uM62.5 uM 31.25 uM 15.62 uM D Cp ds % Radical Scavenging Activity Cp ds % Radical Scavenging Activity Figs. A-D: Free radical scavenging activities of pyrimidine derivatives ( ) on deferent concentrations. onclusion
The present study identifies new series of pyrimidines as potential radical scavengers. All analogues were found to display diverse free radical scavenging potential when compared with the standard butylated hydroxytoluene. Compounds , , , , , and , with IC values of 55.6 ± 2.1, 122.4 ± 1.9, 107.65 ±1.3, 108.4 ± 2.8, 113.4 ±1.3, 42. 9± 0.31, and 65.7 ± 1.80 µ M, respectively, showed good free radical scavenging potential better than the standard butylated hydroxytoluene having IC value of 128.83 ± 2.1 µ M. Cytotoxic evaluation of selected derivatives further support our study. Compound , , and were identified as non-cytotoxic against 3T3 cells; therefore, these can serve as lead compounds for further development as potential drug candidates to scavenge reactive oxygen species. Acknowledgments
The authors are thankful to the Pakistan Academy of Sciences for providing financial support to Project No. (5-9/PAS/440).
References: Neha, K., Haider, M. R., Pathak, A., and Yar, M. S., Medicinal prospects of antioxidants: A review.
European Journal of Medicinal Chemistry , , 687-704 ( ). 2. Suleman, M., Khan, A., Baqi, A., Kakar, M. S., and Ayub, M., Antioxidants, its role in preventing free radicals and infectious diseases in human body.
Pure and Applied Biology , , 380-388 ( . 3. Young, A., and Lowe, G., Carotenoids-antioxidant properties.
Antioxiants , , 28, ( . 4. Qurat-ul-Ain., Choudhary, M.I., and Kochanek, K.S., Modulation of melanoma cell proliferation and spreading by novel small molecular weight antioxidants.
Free Radical Biology and Medicine , , S28 ( . 5. Pisoschi, A. M., and Pop, A., The role of antioxidants in the chemistry of oxidative stress: A review.
European Journal of Medicinal Chemistry , , 55-74 ( ). 6. Ain, Qurat-ul., Study of the Effect of Antioxidant on Oxidative Stress in Molecular and Cellular Models. (Doctoral dissertation, University of Karachi, Karachi), 1-227( ). 7.
Sankarganesh, M., Revathi, N., Raja, J. D., Sakthikumar, K., Kumar, G. G. V., Rajesh, J., and Mitu, L., Computational, antimicrobial, DNA binding and anticancer activities of pyrimidine incorporated ligand and its copper (II) and zinc (II) complexes (II) complexes.
Journal of Serbian Chemical Society , , 277-291( . 8. Haleel, A. K., Rafi, U. M., Mahendiran, D., Mitu, L., Veena, V., and Rahiman, A. K., DNA profiling and in vitro cytotoxicity studies of tetrazolo [1,5-a] pyrimidine-based copper (II) complexes.
Biometals , 1-16 ( ). 9.
Shringare, S. N., Chavan, H. V., Bhale, P. S., Dongare, S. B., Mule, Y. B., Kolekar, N. D., and Bandgar, B. P., Synthesis and pharmacological evaluation of pyrazoline and pyrimidine analogs of combretastatin-A4 as anticancer, anti-inflammatory and antioxidant agents.
Croatica Chemical Acta , , . 10. Wang, Z., Kang, D., Chen, M., Wu, G., Feng, D., Zhao, T., and Daelemans, D., Design, synthesis, and antiviral evaluation of novel hydrazone‐substituted thiophene [3, 2‐d] pyrimidine derivatives as potent human immunodeficiency virus‐1 inhibitors. hemical Biology and Drug Design , , 2009-2021( . 11. Kumar, S., Deep, A., and Narasimhan, B., A. Review on Synthesis, Anticancer and Antiviral Potentials of Pyrimidine Derivatives.
Current Bioactive Compounds , , 289-303( . 12. Selvam, T. P., James, C. R., Dniandev, P. V., and Valzita, S. K., "A mini review of pyrimidine and fused pyrimidine marketed drugs.
Journal of Research in Pharmacy Pract ice, , 01-09 ( . 13. Tokunaga, S., Takashima, T., Kashiwagi, S., Noda, S., Kawajiri, H., Tokumoto, M., and Mizuyama, Y. Neoadjuvant Chemotherapy with Nab-paclitaxel Plus Trastuzumab Followed by 5-Fluorouracil/Epirubicin/Cyclophosphamide for HER2-positive Operable Breast Cancer: A Multicenter Phase II Trial.
Anticancer Research , , 2053-2059 ( ). 14. Ghorab, M. M., andAlsaid, M. S. Anticancer activity of some novel thieno [2, 3-d] pyrimidine derivatives . Biomedical Res earch, , 110-115 ( ). 15. Wilhelm, M., Mueller, L., Miller, M. C., Link, K., Holdenrieder, S., Bertsch, T., and Birkmann, J. Prospective, multicenter study of 5-fluorouracil therapeutic drug monitoring in metastatic colorectal cancer treated in routine clinical practice.
Clinical Colorectal Cancer , , . 16. Smaill, J. B., Gonzales, A. J., Spicer, J. A., Lee, H., Reed, J. E., Sexton, K., and Denny, W. A., Tyrosine kinase inhibitors. 20. Optimization of substituted quinazoline and pyrido [3, 4-d] pyrimidine derivatives as orally active, irreversible inhibitors of the epidermal growth factor receptor family.
Journal Medicinal Chemistry , (17), 8103-8124 ( ). 17. Khan, K. M., Rahim, F., Khan, A., Shabeer, M., Hussain, S., Rehman, W., and Choudhary, M. I., Synthesis and structure–activity relationship of thiobarbituric acid derivatives as potent inhibitors of urease.
Bioorganic and Medicinal Chemistry , , ). 18. Barakat, A., Islam, M. S., Al-Majid, A. M., Ghabbour, H. A., Yousuf, S., Ashraf, M., and Ul-Haq, Z., Synthesis of pyrimidine-2,4,6-trione derivatives: Anti-oxidant, anti-cancer, α-glucosidase, β -glucuronidase inhibition and their molecular docking studies. Bioorganic Chemistry , , 72-79 ( ). 19. Gobbi, L., Grether, U., Guba, W., Kretz, J., Martin, R. E., Westphal, M. V., and I. Jzerman, A. P.
U.S. Patent Application No. 16/228,543 , 1-13 ( . 20.
Reddy, E. K., Remya, C., Sajith, A. M., Dileep, K. V., Sadasivan, C., and Anwar, S., Functionalized dihydroazo pyrimidine derivatives from Morita-Baylis-Hillman acetates: synthesis and studies against acetylcholinesterase as its inhibitors.
RSC Advances , , 77431-77439 ( ). 21. Sahu, M., and Siddiqui, N., A review on biological importance of pyrimidines in the new era.
Journal of Pharmacy and Pharmaceutical Sciences, , 8-21( . 22. Ke, S., Shi, L., Zhang, Z., and Yang, Z., Steroidal [17, 16-d] pyrimidines derived from dehydroepiandrosterone: A convenient synthesis, antiproliferation activity, structure-activity relationships, and role of heterocyclic moiety.
Scientific Reports , , 44439 ( . 3. Khan, K.M., Rahim, F., Shabeer, M., Khan, A., Hussain, S., Rehman, W., Taha, M. Khan, M., Perveen, S. and Choudhary, M. I., Synthesis and structure-activity relationship of thiobarbituric acid derivatives as potent inhibitors of urease. Bioorganic and Medicinal Chemistry , , 4119-4123 ( . 24. Priyadarsini, K. I., Maity, D. K., Naik, G. H., Kumar, M. S., Unnikrishnan, M. K., Satav, J., Mohan G.H., Role of phenolic OH and methylene hydrogen on the free radical reactions and antioxidant activity of curcumin. Free Radical Biology Medicine , , 475-484 ( . 25. Madhu, K., Phytochemical screening and antioxidant activity of in vitro grown plants Clitoria ternatea
L., using DPPH assay.
Asian Journal of Pharmaceutical Clinical Research , , 38-42 ( ). 26. Vemana, H. P., Barasa, L., Surubhotla, N., Kong, J., Ha, S. S., Palaguachi, C., and Dukhande, V. V. Benzimidazole scaffolds as potential anticancer agents: Synthesis and Biological evaluation. The FASEB Journal , , 646-18 ( ..