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Synthesis, characterization, anticancer activity, and molecular docking of some new sugar hydrazone and arylidene derivatives
⁎Address: Department of Chemistry, Turabah University College, Taif University, Box No 311, 21995, Saudi Arabia. s.alosaimi@tu.edu.sa (Saad H. Alotabi)
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Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Peer review under responsibility of King Saud University.
Abstract
New sugar hydrazone moieties, their oxadiazoline derivatives, and arylidene analogues were prepared and chemically elucidated using spectroscopic analysis, such as nuclear magnetic resonance, for hydrogen 1HNMR, carbon 13CNMR, elemental analysis, and Infrared (IR). The prepared compounds were purified and tested against breast cancer cells (MCF-7). Compounds 4c, 4d, 6b, and 6d exhibited moderate to very high anti-breast cancer activity, with a percentage of inhibition of 96.19%, 93.08%, 74.33%, and 86.05% respectively; the reference 5-fluorouracil had an inhibitory percentage of 96.02%.
Keywords
Sugar hydrazones
Arylidene derivatives
Oxadiazolines
Molecular docking
Antimicrobial activity
1 Introduction
The occurrence of many prominent diseases has increased across the globe due to various natural, industrialized, and economic issues (Abu-zaied et al. 2012; Smith et al., 2014). One of the most difficult of these diseases is the mutation and overgrowth of human cellular tissue via cancer. Cancer represents a great risk that can lead to death across the world, claiming the lives of more than 7 million people annually (Abu-zaied et al., 2012; Smith et al., 2014). This number is set to increase annually to 19.3 million by the year 2025 (Ahsan et al., 2014; van der Bilt and Borel Rinkes 2004). An increase in natural and unnatural cancer-causing agents has played a relatively large part in this (Hatti et al., 2015; Seyfried and Shelton 2010). This may be because many different types of cancer have developed in a range of tissues and organs throughout the human anatomical system. The ability of cancer to occur in so many different locations in the human anatomy can make it difficult for medical applications, treatments, and medications to target an ever-changing disease. In addition to developing in different locations throughout the body, there are many types of cancers, malignant and benign, aggressive and slow growing.
Unfortunately, there are no drugs or methods that provide absolute control of the treatment of cancer (Abu-zaied et al., 2012; Smith et al., 2014). A major concern with respect to the pharmaceuticals used in the treatment of cancer is their toxicity. The cytotoxicity of current cancer treatments includes side effects such as bone marrow depression, alopecia, and drug induced cancers, as well as genotoxicity and cancer drug resistance, all of which are compelling reasons to discover innovative approaches to the management of cancer (Ahsan et al., 2014; van der Bilt and Borel Rinkes 2004). Cancer treatments include some therapeutic methods such as hormonal therapy, targeted therapy, radiotherapy, immunotherapy, and chemotherapy (Ahsan et al., 2014; van der Bilt and Borel Rinkes 2004). In addition, solid tumors can be removed surgically or treated in situ using angiogenesis (Ahsan et al., 2014; van der Bilt and Borel Rinkes, 2004).
It is imperative to develop a solution to reduce the projected outcome for this disease (Ahsan et al., 2014; van der Bilt and Borel Rinkes, 2004). Moreover, it is equally important that these methods are economically viable to produce and obtain (Ahsan et al., 2014; van der Bilt and Borel, Rinkes 2004). There are different classes of chemicals that demonstrate promising results for the development of anticancer pharmaceuticals and possibly an array of other anticancer products. One of these, oxadiazoles, are heterocyclic compounds that have many uses in industrial, agricultural, pharmaceutical, and medicinal applications (Sauer et al., 2019; Xu and Mao 2016). Moreover, they have gained suitable proxies for carboxylic acids, esters, and carboxamides (Almasirad et al., 2004). They are manageable and have antifungal, antihypertensive, anti-inflammatory, analgesic, antibacterial, hypoglycemic, antimicrobial, antimalarial, antidepressant, and antitubercular applications (Ahsan et al., 2011; Ahsan et al., 2014; Bakht et al., 2010; Chen et al., 1994). Hydrazones are another group of chemical agents used in many pharmaceutical constituents as well as for biological activities and organic syntheses (Koçyiğit Kaymakçıoğlu and Rollas 2002). They also possess antimicrobial effects. (Cozzini et al., 2008). More importantly, hydrazones derivatives have been recorded to have anti-HIV (Abdel-Aal et al., 2006) as well as anti-cancer properties (El-Faham et al., 2015; Abadi et al., 2003; Cocco et al., 2006; Pandey et al., 2002; Vicini et al., 2006; Zhang et al., 2004). Both oxadiazoles and hydrazones exhibit an array of anti-inflammatory properties. More importantly, they both show promise for use in pharmaceutical and medicinal applications. Positioned at the forefront of innovative future cancer treatments, they are ideal for producing innovative chemical systems to research their effects on cancer and tumor reduction and elimination. In the following article, we describe how hydrazone and oxadiazole derivatives were synthesized and analysed to define their potential properties for their possible use as anti-cancer agents.
2 Experimental section
2.1 Chemistry
Kofler block instruments were used to estimate the melting points (m.p.) of the synthesized compounds. The infrared spectra were measured at the University College of Turbah, Taif University using an ic50 model FTIR (ThermoFisher scientific); KBr discs were used in the spectrometer. NMR spectra for 1HNMR and 13CNMR were measured on an NMR spectrometer at 400 MHz at the Abd-Alaziz King University, Jeddah, Saudi Arabia using tetramethylsilane as a reference. Thin Layer Chromatography using plates (60 F 245) was used to monitor the progress of the reactions. Elemental analyses were determined at Cairo University, Egypt.
2.1.1 Ethyl 2-(4-nitrophenoxy) acetate (2) (Amer et al., 2018)
A mixture of p-aminophenol 1 (10 mmol), anhydrous K2CO3 (10 mmol), ethylchloroacetate (10 mmol), and acetone (25 mL) was heated under reflux for 8 h (TLC). The mixture was filtered off and the filtrate allowed to evaporate under reduced pressure. The resulting precipitate was recrystallized from ethanol to give yellow crystals with a yield of 92%, m.p. 221–223 °C. Rf = 0.55 (5% methanol in methylene chloride). 1H NMR (dimethyl sulfoxide [DMSO]-d6): d = 1.21 (3H, t, J = 7.2 Hz, CH3 CH2), 4.22 (2H, q, J = 7.2 Hz, CH3 CH2), 4.82 (2H, s, CH2), 7.35 (2H, d, J = 5.5 Hz, H-2), 8.22 (2H, d, J = 5.5 Hz, H-3); MS m/z (%) 225 (M+). Anal. Calcd for C10H11NO5: Calcd: C, 53.33; H, 4.92; N, 6.22. Found C, 53.55; H, 5.04; N, 6.49.
2.1.2 2-(4-Nitrophenoxy)acetohydrazide (3) (Amer et al., 2018)
A mixture of 2 (10 mmol), hydrazine hydrate (30 mmol), and ethanol (50 mL) was heated under reflux for 8 h (TLC). The resulting product was filtered off and recrystallized from ethanol to give a white powder with a yield of 95%, m.p. 190–192 °C. Rf = 0.40 (4% methanol in methylene chloride). IR spectra (KBr) (ν, cm−1): 3340 (NH), 3056 (Ar—H), 3455, 3500 (NH2), 1648 (C⚌O), 1574, 1383 (NO2); 1HNMR (DMSO-d6): d = 2.72 (2H, brs, NH2), 4.50 (2H, s, CH2), 7.40 (2H, d, J = 5.5 Hz, Ar—H), 8.18 (2H, d, J = 5.5 Hz, Ar—H), 8.53 (1H, brs, NH); MS m/z (%) 212 (M + H)+. Anal. Calcd for C8H9N3O4: Calcd: C, 45.50; H, 4.30; N, 19.90. Found C, 45.84; H, 4.65; N, 18.10.
2.1.3 Reaction of hydrazide 3 with different aromatic aldehydes to create the corresponding arylidines 4a–d
A solution of 3 (10 mmol) in ethanol was made up, to which aromatic aldehydes (naphthaldehyde, salisaldehyde, p-chlorobenzaldehyde, and furfuraldehyde (10 mmol)) were added. Acetic acid (1 mL) was added to the reaction mixture, which was refluxed for 12 h (TLC). The solvent was evaporated under reduced pressure and the resulting product was filtered to afford 4 (a–d) (85–90% yield).
2.1.3.1 N-(naphthalen-1-ylmethylene)-2-(4-nitrophenoxy)acetohydrazide (4a)
White powder, 85% yield, m.p. 230–232 °C. Rf = 0.72 (10% methanol in methylene chloride). IR spectra (KBr) (ν, cm−1): 3342 (NH), 3056 (Ar—H), 1645 (C⚌O), 1574, 1383 (NO2); 1HNMR (400 MHz, CDCl3): d = 4.58 (2H, s, CH2), 8.05 (1H, brs, NH), 7.18–8.34 (11H, m, CH aromatic), 8.39 (1H, s, CH); 13C NMR (100 MHz, CDCl3): d = 70.59 (CH2), 119.83, 120.02, 121.32, 121.63, 122.71, 124.13, 124.45, 130.54, 130.67, 135.42, 136.28, 1643.09 (Ar—CH), 146.85 (CH), 172.40 (CONH). Anal. Calcd for C18H15N3O4: Calcd: C, 65.32; H, 4.33; N, 12.03. Found: C, 65.44; H, 4.45; N, 11.93.
2.1.3.2 N-(2-hydroxybenzylidene)-2-(4-nitrophenoxy)acetohydrazide (4b)
White powder, 87% yield, m.p. 270–272 °C. Rf = 0.72 (10% methanol in methylene chloride). IR spectra (KBr) (ν, cm−1): 3342 (NH), 3056 (Ar—H), 1645 (C⚌O), 1574, 1383 (NO2); 1HNMR (400 MHz, CDCl3): d = 4.88 (2H, s, CH2), 5.37 (1H, brs, OH), 8.03 (1H, brs, NH), 7.16–8.24 (8H, m, CH aromatic), 8.31 (1H, s, CH); 13C NMR (100 MHz, CDCl3): d = 65.44 (CH2), 115.21, 115.33, 125.70, 125.82, 128.65, 128.86, 140.20, 156.20, 163.60 (Ar—CH), 142.89 (CH), 168.26 (CONH). Anal. Calcd for C15H13N3O5: Calcd: C, 57.14; H, 4.16; N, 13.33. Found: C, 56.07; H, 4.55; N, 14.00.
2.1.3.3 N-(4-chlorobenzylidene)-2-(4-nitrophenoxy)acetohydrazide (4c)
White powder, 90% yield, m.p. >300 °C. Rf = 0.72 (10% methanol in methylene chloride). IR spectra (KBr) (ν, cm−1): 3350 (NH), 3090 (Ar—H), 1643 (C⚌O), 1576, 1387 (NO2); 1HNMR (400 MHz, CDCl3): d = 4.88 (2H, s, CH2), 8.20 (1H, brs, NH), 7.16–8.24 (8H, m, CH aromatic), 8.31 (1H, s, CH); 13C NMR (100 MHz, CDCl3): d = 65.44 (CH2), 115.21, 115.33, 125.70, 125.82, 128.65, 128.86, 140.20, 156.20, 163.60 (Ar—CH), 142.89 (CH, 168.26 (CONH). Anal. Calcd for C15H12ClN3O4: Calcd: C, 53.98; H, 3.62; N, 12.59. Found: C, 54.03; H, 3.77; N, 12.94.
2.1.3.4 N-(furan-2-ylmethylene)-2-(4-nitrophenoxy)acetohydrazide (4d)
White powder, 90% yield, m.p. 200–202 °C. Rf = 0.72 (10% methanol in methylene chloride). IR spectra (KBr) (ν, cm−1): 3335 (NH), 3080 (Ar—H), 1645 (C⚌O), 1575, 1385 (NO2); 1HNMR (400 MHz, CDCl3): d = 4.85 (2H, s, CH2, 7.02 (1H, brs, NH), 6.94–8.27 (8H, m, CH aromatic, 8.33 (1H, s, CH); 13C NMR (100 MHz, CDCl3): d = 65.24 (CH2), 115.17, 115.34, 125.70, 125.82, 124.32, 137.86, 140.95, 149.06, 163.56 (Ar—CH), 145.12 (CH), 167.91 (CONH). Anal. Calcd for C13H11N3O5: Calcd: C, 53.98; H, 3.83; N, 14.53. Found: C, 54.12; H, 3.67; N, 14.86.
2.1.4 Acetylation reaction of arylidene derivatives 4a-d to create the corresponding oxadiazolines 5a-d
A mixture of arylidene derivatives 4a-d (10 mmol) and acetic anhydride (20 mmol) was heated under reflux at 100–120 °C for 4 h (TLC). The resulting mixture was poured on crushed ice, filtered off, and recrystallized from ethanol to yield the oxadiazoline derivatives 5a-d (75–83% yield).
2.1.4.1 1-(2-(Naphthalen-2-yl)-5-((4-nitrophenoxy)methyl)-1,3,4-oxadiazol-3(2H)-yl)ethanone (5a)
Yellow gum, 75% yield. Rf = 0.72 (10% methanol in methylene chloride). IR spectra (KBr) (ν, cm−1): 3056 (Ar—H), 1576, 1385 (NO2), 1450 (CH2), 1375 (CH3); 1HNMR (400 MHz, CDCl3): d = 1.99 (3H, s, COCH3), 4.45 (2H, s, CH2), 6.86 (1H, s, CH), 7.17–8.18 (11H, m, CH aromatic). Anal. Calcd for C21H17N3O5: Calcd: C, 64.45; H, 4.38; N, 10.74. Found: C, 63.91; H, 4.45; N, 11.00.
2.1.4.2 1-(2-(2-Hydroxyphenyl)-5-((4-nitrophenoxy)methyl)-1,3,4-oxadiazol-3(2H)-yl)ethanone (5b)
Yellow gum, 80% yield. Rf = 0.72 (10% methanol in methylene chloride). IR spectra (KBr) (ν, cm−1): 3275 (OH), 3070 (Ar—H), 1576, 1385 (NO2), 1455 (CH2), 1380 (CH3); 1HNMR (400 MHz, CDCl3): d = 2.04 (3H, s, COCH3), 4.63 (2H, s, CH2), 5.37 (1H, brs, OH), 6.73 (1H, s, CH), 6.96–8.20 (11H, m, CH aromatic). Anal. Calcd for C17H15N3O6: Calcd: C, 57.14; H, 4.23; N, 11.76. Found: C, 57.48; H, 4.65; N, 11.54.
2.1.4.3 1-(2-(4-Chlorophenyl)-5-((4-nitrophenoxy)methyl)-1,3,4-oxadiazol-3(2H)-yl)ethanone (5c)
Brown gum, 77% yield. Rf = 0.72 (10% methanol in methylene chloride). IR spectra (KBr) (ν, cm−1): 3085 (Ar—H), 1575, 1385 (NO2), 1450 (CH2), 1382 (CH3); 1HNMR (400 MHz, CDCl3): d = 2.11 (3H, s, COCH3), 4.63 (2H, s, CH2), 6.67 (1H, s, CH), 7.25–8.15 (8H, m, CH aromatic). Anal. Calcd for C17H14ClN3O5: Calcd: C, 54.34; H, 3.67; N, 11.18. Found: C, 54.43; H, 3.61; N, 11.34.
2.1.4.4 1-(2-(Furan-2-yl)-5-((4-nitrophenoxy)methyl)-1,3,4-oxadiazol-3(2H)-yl)ethanone (5d)
Brown gum, 83% yield. Rf = 0.72 (10% methanol in methylene chloride). IR spectra (KBr) (ν, cm−1): 3090 (Ar—H), 1572, 1380 (NO2), 1450 (CH2), 1375 (CH3); 1HNMR (400 MHz, CDCl3): d = 2.07 (3H, s, COCH3), 4.60 (2H, s, CH2), 6.88 (1H, s, CH), 6.40–8.12 (7H, m, CH aromatic);. Anal. Calcd for C15H13N3O6: Calcd: C, 54.38; H, 3.96; N, 12.68. Found: C, 54.52; H, 3.77; N, 12.50.
2.1.5 Reaction of hydrazide 3 with different sugars to create the corresponding sugar hydrazone derivatives 6a-d
To a solution of 3 (10 mmol) in ethanol, different sugar moieties (10 mmol) were added and the reaction mixture was allowed to reflux for 1 h. Acetic acid (1 mL) was added and the reaction was heated for 8 h under reflux (TLC). The solvent was allowed to evaporate under reduced pressure and the resulting product was filtered to afford 6a-d (80–92% yield).
2.1.5.1 L-(-)–Arabinose-2-(4-nitrophenoxy-2-yl)acetohydrazide (6a)
Pale yellow powder, 82% yield, m.p. 178–180 °C. Rf = 0.65 (5% MeOH in CH2Cl2), 1H NMR (CDCl3-d6): δ = 2.75 (1H, brs, OH), 3.12–3.85 (5H, H-2, H-3, H-4, H-5, H5′, m, 5H), 3.54–3.63 (3H, brs, 3xOH), 4.60 (2H, s, CH2), 7.12 (1H, brs, NH), 7.20–8.10 (4H, m, Ar—H), 7.52 (1H, s, CH); 13C NMR (100 MHz, CDCl3): d = 66.54 (CH2OH), 66.90, 72.43, 73,98 (CH of sugar), 68.64 (CH2), 119.93, 120.12, 130.58, 130.63, 146.27, 167.84, (Ar—CH), 154.49 (CH), 171.36 (CONH). Anal. Calcd for C13H17N3O8: Calcd: C, 45.48; H, 4.99; N, 12.24. Found: C, 45.32; H, 4.57; N, 12.73.
2.1.5.2 D-(-)–Mannose-2-(4-nitrophenoxy-2-yl)acetohydrazide (6b)
White powder, 85% yield, m.p. 200–202 °C. Rf = 0.65 (5% MeOH in CH2Cl2), 1H NMR (CDCl3-d6): δ = 2.85 (1H, brs, OH), 3.27–3.80 (6H, H-2, H-3, H-4, H-5, H-6, H6′, m, 6H), 3.57–3.66 (4H, brs, 4xOH), 4.65 (2H, s, CH2), 7.15 (1H, brs, NH), 7.23–8.17 (4H, m, CH aromatic), 7.55 (1H, s, CH); 13C NMR (100 MHz, CDCl3): d = 67.27 (CH2OH), 67.89, 70.71, 71,76, 72.99 (CH of sugar), 68.80 (CH2), 119.90, 120.07, 130.49, 130.62, 146.16, 168.72, (Ar—CH), 146.62 (CH, 175.11 (CONH). Anal. Calcd for C14H19N3O9: Calcd: C, 45.04; H, 5.13; N, 11.26. Found: C, 45.22; H, 4.98; N, 11.67.
2.1.5.3 D-(-)–Galactose- 2-(4-nitrophenoxy-2-yl)acetohydrazide (6c)
White powder, 90% yield, m.p. 215–217 °C. Rf = 0.65 (5% MeOH in CH2Cl2), 1H NMR (CDCl3-d6): δ = 2.79 (1H, brs, OH), 3.25–3.82 (6H, H-2, H-3, H-4, H-5, H-6, H6′, m, 6H), 3.55–3.64 (4H, brs, 4xOH), 4.63 (2H, s, CH2), 7.10 (1H, brs, NH), 7.25–8.15 (4H, m, CH aromatic), 7.50 (1H, s, CH); 13C NMR (100 MHz, CDCl3): d = 67.30 (CH2OH), 67.90, 70.73, 71,77, 72.97 (CH of sugar), 68.80 (CH2), 119.91, 120.09, 130.50, 130.63, 146.17, 168.74, (Ar—CH), 146.65 (CH, 175.14 (CONH). Anal. Calcd for C14H19N3O9: Calcd: C, 45.04; H, 5.13; N, 11.26. Found: C, 45.25; H, 5.08; N, 11.53.
2.1.5.4 D-(-)–Glucose- 2-(4-nitrophenoxy-2-yl)acetohydrazide (6d)
White powder, 92% yield, m.p. 250–252 °C. Rf = 0.65 (5% MeOH in CH2Cl2), 1H NMR (CDCl3-d6): δ = 2.81 (1H, brs, OH), 3.22–3.81 (6H, H-2, H-3, H-4, H-5, H-6, H6′, m, 6H), 3.52–3.67 (4H, brs, 4xOH), 4.61 (2H, s, CH2), 7.12 (1H, brs, NH), 7.20–8.10 (4H, m, CH aromatic), 7.53 (1H, s, CH); 13C NMR (100 MHz, CDCl3): d = 66.78 (CH2OH), 70.79, 71,56, 72.97, 75.05 (CH of sugar), 68.88 (CH2), 119.85, 120.00, 130.49, 130.60, 146.08, 168.77, (Ar—CH), 146.70 (CH), 176.12 (CONH). Anal. Calcd for C14H19N3O9: Calcd: C, 45.04; H, 5.13; N, 11.26. Found: C, 45.20; H, 5.05; N, 11.50.
2.1.6 Acetylation of sugar hydrazone derivatives 6a-d to give the corresponding acetylated sugar hydrazones 7a-d
A mixture of 6a-d (10 mmol) was dissolved in pyridine (25 mL) and acetic anhydride (15 mmol). The mixture was stirred overnight (TLC). The resulting solution was poured on 50 g ice water and the resulting products were filtered off to afford 7a-d (78–83% yield).
2.1.6.1 2,3,4,5-Tetra-O-acetyl-L-(-)-arabinose-2-(4-nitrophenoxy-2-yl)acetohydrazide (7a)
Brown gum, 78% yield. Rf = 0.72 (5% MeOH in CH2Cl2). 1H NMR (CDCl3-d6): δ = 2.04, 2.07, 2.11, 2.16 (12H, 4s, 4xCOCH3), 4.68 (2H, s, CH2), 4.48, 4.52 (2H, m, H-5, H-5′), 4.58 (1H, s, H-2), 4.92 (1H, s, H-4), 4.95 (1H, s, H-3), 7.12 (brs, 1H, NH), 7.50 (1H, d, J = 5.5 Hz, H-1), 7.23–8.12 (4H, m, CH aromatic); 13C NMR (100 MHz, CDCl3): d = 20.38, 20.52, 20.99, 22.41 (4CH3 of 4xOCOCH3), 58.55, 62.24, 66.24 (3CH of sugar), 66.24 (CH2 of sugar), 66.93 (CH2), 115.11, 115.28, 123.90, 125.71, 141.07, 163.17 (CH of Ar—H), 149.53 (CH), 170.11 (4CO of 4xOCOCH3). Anal. Calcd for C21H25N3O12: Calcd: C, 49.32; H, 4.93; N, 8.22. Found: C, 49.67; H, 4.88; N, 8.37.
2.1.6.2 2,3,4,5-Penta-O-acetyl-D-(-)-mannose-2-(4-nitrophenoxy-2-yl)acetohydrazide (7b)
Brown gum, 80% yield. Rf = 0.72 (5% MeOH in CH2Cl2). 1H NMR (CDCl3-d6): δ = 1.98, 2.03, 2.05, 2.13, 2.15 (15H, 5s, 5xCOCH3), 4.50 (2H, s, CH2), 4.12, 4.16 (2H, m, H-6, H-6′), 4.88 (1H, s, H-2), 5.08 (1H, s, H-5), 5.28 (1H, s, H-4), 5.35 (1H, s, H-3), 7.07 (brs, 1H, NH), 7.16 (1H, d, J = 5.5 Hz, H-1), 7.20–8.26 (4H, m, CH aromatic); 13C NMR (100 MHz, CDCl3): d = 20.38, 20.46, 20.71, 21.00, 22.30 (5CH3 of 5xOCOCH3), 61.83, 62.15, 64.97, 65.20 (4CH of sugar), 67.82 (CH2 of sugar), 68.49 (CH2), 115.24, 115.35, 125.67, 125.75, 141.50, 163.03 (CH of Ar—H), 149.55 (CH), 170.29 (5CO of 5xOCOCH3), 172.00 (CO). Anal. Calcd for C24H29N3O14: Calcd: C, 49.40; H, 5.01; N, 7.20. Found: C, 49.82; H, 4.92; N, 7.42.
2.1.6.3 2,3,4,5-Penta-O-acetyl-D-(-)-galactose-2-(4-nitrophenoxy-2-yl)acetohydrazide (7c)
Brown gum, 81% yield. Rf = 0.72 (5% MeOH in CH2Cl2). 1H NMR (CDCl3-d6): δ = 2.00, 2.05, 2.07, 2.12, 2.14 (15H, 5 s, 5xCOCH3), 4.53 (2H, s, CH2), 4.15,4.18 (2H, m, H-6, H-6′), 4.86 (1H, s, H-2), 5.10 (1H, s, H-5), 5.25 (1H, s, H-4), 5.29 (1H, s, H-3), 7.00 (brs, 1H, NH), 7.15 (1H, d, J = 5.5 Hz, H-1), 7.22–8.21 (4H, m, CH aromatic); 13C NMR (100 MHz, CDCl3): d = 20.38, 20.44, 20.76, 21.05, 22.35 (5CH3 of 5xOCOCH3), 61.73, 62.25, 64.88, 65.30 (4CH of sugar), 66.50 (CH2 of sugar), 69.12 (CH2), 115.24, 115.35, 125.37, 125.67, 141.30, 163.30 (CH of Ar—H), 150.07 (CH), 170.00 (5CO of 5xOCOCH3), 172.12 (CO). Anal. Calcd for C24H29N3O14: Calcd: C, 49.40; H, 5.01; N, 7.20. Found: C, 49.65; H, 5.12; N, 6.98.
2.1.6.4 2,3,4,5-Penta-O-acetyl-D-(-)-glucose-2-(4-nitrophenoxy-2-yl)acetohydrazide (7d)
Brown gum, 83% yield. Rf = 0.72 (5% MeOH in CH2Cl2). 1H NMR (CDCl3-d6): δ = 1.99, 2.00, 2.02, 2.08, 2.09 (15H, 5s, 5xCOCH3), 4.82 (2H, s, CH2), 4.69, 4.80 (2H, m, H-6, H-6′), 4.88 (1H, s, H-2), 4.94 (1H, s, H-5), 4.96 (1H, s, H-4), 5.30 (1H, s, H-3), 7.06 (brs, 1H, NH), 7.13 (1H, d, J = 5.5 Hz, H-1), 7.19–8.23 (4H, m, CH aromatic); 13C NMR (100 MHz, CDCl3): d = 20.32, 20.49, 20.57, 20.77, 21.00 (5CH3 of 5xOCOCH3), 61.94, 62.10, 65.07, 65.14 (4CH of sugar), 67.21 (CH2 of sugar), 68.93 (CH2), 115.13, 115.26, 125.61, 125.71, 141.42, 163.68 (CH of Ar—H), 149.55 (CH), 169.63 (5CO of 5xOCOCH3), 170.07 (CO). Anal. Calcd for C24H29N3O14: Calcd: C, 49.40; H, 5.01; N, 7.20. Found: C, 49.53; H, 5.17; N, 6.99.
2.1.7 General procedure for the synthesis of 4-acetyl-5-(tetra-and penta-O-acetylalditolyl)-2-(4-nitrophenoxy-2-yl)-1,3,4-oxadiazoline (8a-d)
A solution of sugar hydrazones 6a-d (10 mmol) was dissolved in 10 mL acetic anhydride and allowed to reflux at 95 °C for 4 h (TLC). The resulting solution was poured onto 50 g ice water and then the resultant precipitate was filtered off, washed with water, and dried to give 8a-d (72–76% yield).
2.1.7.1 4-Acetyl-5-(1,2,3,4-tetra-O-acetyl-L-arabinotetritolyl)-2-(4-nitrophenoxy-2-yl)-1,3,4-oxadiazoline (8a)
Yellow gum, 74% yield. Rf = 0.72 (5% MeOH in CH2Cl2). 1H NMR (CDCl3-d6): δ = 2.05, 2.07, 2.10, 2.15, 2.21 (15H, m, 5xCOCH3), 3.42 (2H, s, CH2), 4.22, 4.31 (2H, m, H-5, H-5′), 5.13 (1H, m, H-3), 5.16 (1H, m, H-4), 5.18 (1H, m, H-2), 5.28 (1H, d, j = 5.5 Hz, H-1), 7.22–8.30 (4H, m, CH aromatic); 13C NMR (100 MH, CDCl3): d = 20.45, 20.50, 20.78, 21.00, 24.58 (5CH3 of 5xCOCH3), 63.36 (CH2 of sugar), 64.96, 68.44, 76.49 (3CH of sugar), 71.49 (CH2), 76.95 (CH of oxadiazolines), 115.14, 115.33, 125.75, 125.81, 141.19, 162.65, 163.02 (CH of Ar—H), 169.28, 169.35, 169.76, 170.08, 172.01 (5CO of 5xCOCH3). Anal. Calcd for C23H27N3O13: Calcd: C, 49.91; H, 4.92; N, 7.95. Found: C, 49.80; H, 5.07; N, 8.02.
2.1.7.2 4-Acetyl-5-(1,2,3,4,5-penta-O-acetyl-D-mannopentitolyl)-2-(4-nitrophenoxy-2-yl)-1,3,4-oxadiazoline (8b)
Yellow gum, 72% yield. Rf = 0.72 (5% MeOH in CH2Cl2). 1H NMR (CDCl3-d6): δ = 2.09, 2.10, 2.11, 2.12, 2.14, 2.17 (18H, m, 6xCOCH3), 3.41 (2H, s, CH2), 4.54, 4.88 (2H, m, H-6, H-6′), 5.05 (1H, m, H-3), 5.06 (1H, m, H-4), 5.07 (1H, m, H-5), 5.19 (1H, m, H-2), 5.28 (1H, d, j = 5.5 Hz, H-1), 7.21–8.28 (4H, m, CH aromatic); 13C NMR (100 MH, CDCl3): d = 20.18, 20.26, 20.40, 20.48, 20.75, 21.01 (6CH3 of 6xCOCH3), 65.00 (CH2 of sugar), 66.32, 67.22, 67.49, 67.80 (4CH of sugar), 71.28 (CH2), 79.11 (CH of oxadiazolines), 115.14, 115.35, 115.59, 125.75, 141.16, 163.05, 169.19 (CH of Ar—H), 169.35, 169.42, 169.60, 170.00, 172.01 (5CO of 5xCOCH3). Anal. Calcd for C26H31N3O15: Calcd: C, 49.92; H, 5.00; N, 6.72. Found: C, 50.05; H, 5.12; N, 6.38.
2.1.7.3 4-Acetyl-5-(1,2,3,4,5-penta-O-acetyl-D-galactopentitolyl)-2-(4-nitrophenoxy-2-yl)-1,3,4-oxadiazoline (8c)
Yellow gum, 75% yield. Rf = 0.72 (5% MeOH in CH2Cl2). 1H NMR (CDCl3-d6): δ = 2.12, 2.14, 2.15, 2.17, 2.19, 2.22 (18H, m, 6xCOCH3), 3.50 (2H, s, CH2), 4.24,4.55 (2H, m, H-6, H-6′), 5.07 (1H, m, H-3), 5.09 (1H, m, H-4), 5.11 (1H, m, H-5), 5.22 (1H, m, H-2), 5.35 (1H, d, j = 5.5 Hz, H-1), 7.25–8.15 (4H, m, CH aromatic); 13C NMR (100 MH, CDCl3): d = 20.08, 20.21, 20.28, 20.40, 21.35, 22.00 (6CH3 of 6xCOCH3), 63.00 (CH2 of sugar), 67.12, 67.42, 67.60, 68.53 (4CH of sugar), 73.29 (CH2), 77.08 (CH of oxadiazolines), 115.24, 115.35, 125.19, 125.45, 141.34, 163.15, 169.76 (CH of Ar—H), 170.25, 170.53, 170.82, 171.11, 172.05 (5CO of 5xCOCH3). Anal. Calcd for C26H31N3O15: Calcd: C, 49.92; H, 5.00; N, 6.72. Found: C, 49.88; H, 4.96; N, 6.53.
2.1.7.4 4-Acetyl-5-(1,2,3,4,5-penta-O-acetyl-D-galactopentitolyl)-2-(4-nitrophenoxy-2-yl)-1,3,4-oxadiazoline (8d)
Yellow gum, 76% yield. Rf = 0.72 (5% MeOH in CH2Cl2). 1H NMR (CDCl3-d6): δ = 1.99, 2.00, 2.05, 2.07, 2.09, 2.12 (18H, m, 6xCOCH3), 3.39 (2H, s, CH2), 4.22, 4.50 (2H, m, H-6, H-6′), 5.08 (1H, m, H-3), 5.11 (1H, m, H-4), 5.14 (1H, m, H-5), 5.20 (1H, m, H-2), 5.32 (1H, d, j = 5.5 Hz, H-1), 7.20–8.18 (4H, m, Ch aromatic); 13C NMR (100 MH, CDCl3): d = 20.10, 20.22, 20.34, 20.42, 21.40, 22.08 (6CH3 of 6xCOCH3), 63.04 (CH2 of sugar), 67.15, 68.32, 68.50, 68.67 (4CH of sugar), 73.30 (CH2), 78.00 (CH of oxadiazolines), 115.34, 115.43, 125.22, 125.57, 141.50, 164.25, 168.26 (CH of Ar—H), 170.25, 171.33, 171.65, 172.23, 172.75 (5CO of 5xCOCH3). Anal. Calcd for C26H31N3O15: Calcd: C, 49.92; H, 5.00; N, 6.72. Found: C, 49.98; H, 5.22; N, 7.06.
2.2 Computational study
Chemical structure information was noted from the optimization geometries of the molecular structures. In addition, the chemical constituents were incorporated with the binding sites as noted from previous crystal structure publications.
2.2.1 Selection of protein structures
To target active sites, experimental docking procedures were carried out on DNA gyrase B (ID: 4uro) (Dale et al., 1999), cathepsin B (ID: 1gmy) (Greenspan et al., 2003) and thymidylate synthase (PDB: 1NJE) (Finer-Moore et al., 1996) using MOE 2015 (Montreal 2009). Preparation procedures for the MOE were carried out to eliminate errors due to the active sites. The addition of hydrogens and the calculation of the partial charges (AMBER12: EHT) were compiled after corrections. In addition, the minimization (AMBER12: EHT, root mean square gradient: 0.100) was carried out.
2.2.2 Binding site analysis
Identification of the binding sites of the receptors was made possible using MOE Site Finder software. MOE Site Finder computes putative binding sites based on protein information and geometrical points from tridimensional conformations. The fundamentals for this method models alpha spheres as generalized convex hulls (Soga, Shirai, Kobori & Hirayama, 2007).
2.2.3 MOE site Finder identifies the confirmed co-crystalized ligands in the holoforms. MOE stepwise docking method
The enzyme crystal structures were analyzed along with the removal of inhibitor molecules and water, after which the addition of hydrogen atoms became immediately necessary. Subsequently, the MMFF94x force field allotted scores for the parameters and charges. After this, the module mode of the MOE helped with sphere production following the alpha-site. The triangular matcher placement method helps determine generations of the optimized 3D structure of molecules for an array of ligand postures. The triangular matcher technique used postures by aligning them with ligand triplets to subsequent atoms relative to triplets of alpha spheres distinguished by the points of the receptor site. For this structure, any corresponding alpha sphere was used for the determination of the postures during the iterations. The London dG scoring function was used to generate the pose refined with solvation effects. The final energy was calculated with the use of the Generalized Born solvation model (GB/VI) and final poses were allotted scores relative to the free energy measured in kcal/mol.
2.3 Anti-cancer screening
2.3.1 Cell line propagation
Cells were established and then propagated in Dulbecco’s modified Eagle’s medium (DMEM), which consisted of 50 µg/mL gentamycin, 1% L-glutamine, 10% heat-inactivated fetal bovine serum, and HEPES buffer. The cells were maintained in a 37 °C atmospheric environment and sub-cultured twice weekly (Mosmann et al., 1983). Cytotoxicity was evaluated using a viability assay in which the cells were seeded at a concentration level of 1 × 104 per well in a 96 well plate with 100 µL growth medium. After 24 h, medium was added at a different concentration. With a multichannel pipette, the serial two-fold dilution of the chemical compound being tested was aliquoted to the confluent cells. The monolayers were dispensed into a 96 well plate. The microtiter plates were incubated at 37 °C and 5% CO2 for 48 h with humidity. The test sample concentration was added to three wells. The control cells were incubated without the inclusion of any of the test samples and with and without the addition of DMSO. The maximum amount of DMSO added (0.1%) was deemed to have no effect on the control wells or on the experimental results. Following cell incubation at 37 °C, different sample concentrations were produced and incubated for 24 h. A colorimetric technique was used to determine cell yield. After incubation, a 1% Violet Crystal solution was placed in the remaining cell media in each well for the remainder of the 30 min. Using tap water, the plates were rinsed to remove all of the remaining stain. Following addition of a solution of 30% glacial acetic acid solution to the wells, absorbance was measured at 490 nm; the spectroscopic background correction was provided by measuring a well without stain (TECAN Inc.). Samples were compared to the cell controls, which lacked any of the compounds tested. The experiment was carried out in triplicate and cytotoxicity effectiveness was calculated. The optical density of the sample was detected using a microplate reader. Determination of the viable cells along with the viability percentage was carried out using the following equation: [(ODt/ODc)] × 100%, where ODt is the mean optical density of all the wells treated with the test sample and ODc is the mean optical density of the untreated cells. To understand the degree of survival of a tumor cell line after treatment, a graph of surviving cells and drug concentration was plotted Gomha et al., 2015. Graphic plots of the dose-response curve for all of the concentrations helped to determine the estimation of the IC50 of intact cells (GraphPad Prism software; San Diego, CA, USA).
3 Results and discussion
3.1 Chemistry
1,3,4-Oxadiazole and 1,3,4-oxadiazoline analogues play an important role in bioorganic and medicinal chemistry owing to their anticancer, antimicrobial, antifungal, and anti-inflammatory activities Muhi-eldeen et al., 2008. We synthestized the compounds of interest as follows: 4-nitrophenol (1) was allowed to react with ethylchloroacetate and anhydrous K2CO3 in acetone under reflux to produce ethyl 2-(4-nitrophenoxy) acetate (2) with a yield of 92%. Structural analyses performed using 1HNMR showed a triplet at 1.21 for CH3, a quartet at 4.22 for CH2, a singlet at 4.82 for CH2, and doublets at 7.35 and 8.22 for the aromatic system. Ester-2 and hydrazine hydrate reacted in ethanol under reflux to produce 2-(4-nitrophenoxy)acetohydrazide (3) with a yield of 95% (Scheme 1). Structural analyses of compound 3 performed using 1HNMR showed a doublet at 2.72 for NH2 and broad single at 8.53 for NH. The IR spectra exhibited one peak at 3340 for NH, two peaks at 3340 and 3500 for NH2 (NH), and a peak at 1648 for (CONH).
Hydrazide 3 was reacted with several aldehyde derivatives (naphthaldehyde, salicaldehyde, p-chlorobenzaldehyde, and furfuraldehyde) in ethanol with acetic acid as a catalyst to produce the arylidene derivatives 4a-d with a yield of 85–90%. The synthesized compounds were analysed using 1HNMR, which exhibited a doublet around 4.58 for CH2, a broad single around 8 for NH, a multiplet around 7.18–8.34 for the aromatic ring, and a singlet around 8.39 for the CH group. 13CNMR analysis exhibited a singlet around 65 for CH2, a multiplet in the range from 115 to 163 for the aromatic system, and a singlet around 163 for CH. Arylidene derivatives cyclized using acetic anhydride under reflux produced the oxadiazoline derivatives 5a-d with a yield of 75–83% (Scheme. 2). The chemical structures of the oxadiazoline derivatives 5a-d, confirmed using IR, exhibited a peak around 3050 for Ar—H, a peak around 1450 for CH2, and a peak around 1375 for CH3. Analysis using 1HNMR showed a singlet around 6.86 for CH and a multiplet around 7.17 to 8.18 for Ar—H.
Hydrazide-3 was reacted with different monosaccharaides (L-arabinose, D-mannose, D-galactose, and D-glucose) in ethanol followed by addition of acetic acid as catalyst to produce the sugar hydrazone derivatives 6a-d with a yield of 80–92%. The chemical structures of sugar hydrazone derivatives 6a-d were analysed using 1HNMR, which showed broad peaks around 2.75 to 3.63 for the sugar hydroxyl group (OH) and a multiplet around 3.12 to 3.85 for the sugar methin group (CH). Analysis carried out using 13CNMR showed a doublet around 65.54 for the hydroxyl methyl group (CH2OH) and a multiplet around 66.90 to 73.98 for sugar (CH). The sugar hydrazone derivatives 6a-d were acetylated at room temperature using acetic anhydride in pyridine to produce the acetylated sugar hydrazone derivatives 7a-d with a yield of 78–83%. The chemical structures of the acetylated sugar hydrazone derivatives 7a-d were confirmed using 1HNMR. A singlet was detected around 2.04 to 2.15 for the sugar acetyl groups (COCH3), which indicates that all hydroxyl groups were converted to acetyl groups; a singlet around 4.48 to 4.95 was detected for the sugar (CH) group. Analysis with 13CNMR showed a doublet around 20.38 to 22.41 for the CH3 of COCH3, a singlet around 149.53 for the methin group (CH), and a singlet around 170 for the carbonyl of the acetyl group. The sugar hydrazone derivatives 6a-d were acetylated using acetic anhydride under reflux to produce the oxadiazoline derivatives 8a-d with a yield of 72–76% (Scheme 3). The chemical structures of the oxadiazoline derivatives were confirmed using 1HNMR, with a multiplet around 2.00 to 2.20 detected for COCH3 and a multiplet around 4.54 to 5.28 for the sugar (CH) group. Analysis performed with 13CNMR showed a singlet around 20.18 to 21.01 for the CH3 of COCH3, a multiplet around 66.32 to 67.80 for the sugar (CH) group, a singlet around 79.11 for (CH) of oxadiazolines, a singlet around 65.00 for the sugar methylene group, and a multiplet around the range from 169.35 to 172.01 for the (CO) groups.
3.2 Anti-cancer activity
The anti-cancer activity of the synthesized arylidines and sugar hydrazone derivatives 6d, 4d, 6b, and 4c were tested against the breast cancer MCF-7 cell line. The antineoplastic agent 5-fluorouracil (5-FU), a pyrimidine analogue, was used as standard. Table 4 and Fig. 1 showed that the synthesized arylidene derivative 4c exhibited very high activity against the MCF-7 cell line, with 96.19% inhibition against breast cancer cells; the corresponding inhibition for the standard 5-FU was 96.02% (Table 5 and Fig. 8). The arylidene derivative 4d (Table 2 and Fig. 2) exhibited high activity against the MCF-7 cell line, with an inhibition of 93.08%. On the other hand, the sugar hydrazone derivatives 6b and 6d (Tables 3 and 1 and Figs. 3 and 1, respectively) showed more moderate activity against the MCF-7 cell line, with inhibition of 86.05% and 74.33%, respectively (see Figs. 4 and 5).
| Sample concentration (µg/mL) | Viability (%) | Inhibition (%) | SD (±) |
|---|---|---|---|
| 500 | 25.67 | 74.33 | 0.54 |
| 250 | 39.52 | 60.48 | 1.97 |
| 125 | 60.81 | 39.19 | 1.23 |
| 62.5 | 82.94 | 17.06 | 0.42 |
| 31.25 | 93.56 | 6.44 | 0.38 |
| 15.6 | 98.73 | 1.27 | 0.19 |
| 7.8 | 100 | 0 | – |
| 3.9 | 100 | 0 | – |
| 0 | 100 | 0 | – |
| Sample concentration (µg/mL) | Viability (%) | Inhibition (%) | SD (±) |
|---|---|---|---|
| 500 | 6.92 | 93.08 | 0.46 |
| 250 | 17.43 | 82.57 | 0.91 |
| 125 | 29.45 | 70.55 | 0.52 |
| 62.5 | 41.89 | 58.11 | 1.97 |
| 31.25 | 59.43 | 40.57 | 0.89 |
| 15.6 | 78.15 | 21.85 | 0.43 |
| 7.8 | 90.68 | 9.32 | 0.16 |
| 3.9 | 97.43 | 2.57 | 0.05 |
| 0 | 100 | 0 | – |
| Sample concentration (µg/mL) | Viability (%) | Inhibition (%) | SD (±) |
|---|---|---|---|
| 500 | 13.95 | 86.05 | 0.31 |
| 250 | 25.84 | 74.16 | 0.18 |
| 125 | 38.74 | 61.26 | 0.62 |
| 62.5 | 49.27 | 50.73 | 0.84 |
| 31.25 | 67.59 | 32.41 | 0.97 |
| 15.6 | 88.91 | 11.09 | 0.13 |
| 7.8 | 95.42 | 4.58 | 0.25 |
| 3.9 | 99.76 | 0.24 | 0.11 |
| 0 | 100 | 0 | – |
| Sample concentration (µg/ml) | Viability (%) | Inhibitory (%) | SD (±) |
|---|---|---|---|
| 500 | 3.81 | 96.19 | 0.75 |
| 250 | 6.45 | 93.55 | 0.29 |
| 125 | 11.28 | 88.72 | 0.41 |
| 62.5 | 18.74 | 81.26 | 0.62 |
| 31.25 | 30.97 | 69.03 | 0.75 |
| 15.6 | 43.25 | 56.75 | 1.34 |
| 7.8 | 59.13 | 40.87 | 1.95 |
| 3.9 | 70.84 | 29.16 | 0.69 |
| 0 | 100 | 0 | – |
| Sample concentration (µg/mL) | Viability (%) | Inhibition (%) | SD (±) |
|---|---|---|---|
| 500 | 3.98 | 96.02 | 0.16 |
| 250 | 8.12 | 91.88 | 0.24 |
| 125 | 14.91 | 85.09 | 0.33 |
| 62.5 | 27.84 | 72.16 | 0.18 |
| 31.25 | 39.58 | 60.42 | 0.62 |
| 15.6 | 46.79 | 53.21 | 2.31 |
| 7.8 | 62.43 | 37.57 | 1.69 |
| 3.9 | 78.15 | 21.85 | 0.41 |
| 0 | 100 | 0 | – |
3.3 Docking studies
The docking study targeted DNA gyrase, cathepsin B, and thymidylate synthase to examine the mode of action of these small compounds as antitumor agents. The ligand–protein interaction behavior was estimated based on docking score function as implemented in MOE 2015.10 (Montreal 2009). All calculations for the docking experiment are shown in Table 6. The crystal structures of DNA gyrase (PDB: 4uro) (Dale et al., 1999), cathepsin B (PDB: 1gmy) (Greenspan et al., 2003), and thymidylate synthase (PDB: 1NJE) (Finer-Moore et al., 1996) were obtained from the literature. The compounds 6b and 4c were docked into active sites on the receptors. The ligands were complexed with active sites of the enzymes. The extracted docked poses of the ligands were energy minimized using a molecular mechanics (Amber12: EHT) force field as the gradient convergence peaked at 0.05 kcal/mol. The highest MOE scoring functions for the compounds tested were investigated to monitor the binding affinities (Table 6). The compounds 6b and 4c exhibited a binding affinity with DNA gyrase of −5.528 and −5.894 kcal/mol, respectively (Table 6). With cathepsin B, these ligands (6b and 4c) had MOE scores of −5.528 and −5.894 kcal/mol, respectively.
| PDB: 4uro | ||||||
|---|---|---|---|---|---|---|
| mol | E.dGE | E_conf | E_place | E.Int. | Eele | rmsd_ |
| 6b | −5.528 | 118.173 | −45.092 | −10.439 | −11.246 | 1.544 |
| 4c | −5.894 | 194.610 | −62.159 | −9.557 | −21.587 | 3.626 |
| PDB:1gmy | ||||||
| mol | E.dGE | E_conf | E_place | E.Int. | Eele | rmsd_ |
| 6b | −5.951 | 184.486 | −63.644 | −10.585 | −12.295 | 2.405 |
| 4c | −5.401 | 113.259 | −47.995 | −9.652 | −20.316 | 2.840 |
E_score1; initial free binding energy of the ligand from a given pose. Ed.G.: final free binding energy of the ligand from a given pose, E_conf; free binding energy of the ligand from a given conformer. E_place. free binding energy of the ligand from a receptor. E.Int.: affinity binding energy of ligand with receptor, Eele: electrostatic interaction with the receptor. RMSD; the root mean square deviation of the pose from the docking pose compared to the co-crystal ligand position.
6b and 4c combined with an important amino acid residue (Gly125) at the DNA gyrase active site, where they formed strong hydrogen bonds with equal bond distances of about 2.9° (Figs. 6 and 7; Table 7). These compounds were arranged in parallel mode with Asn54 and Thr126, which are the hydrophilic key that stabilizes these compounds in the receptor. Additionally, Compound 4c acts as a cysteine proteinase inhibitor through the caped binding pocket of cathepsin B by forming important bonds with the vital amino acid Cys29 in the active site. The thiol portion of Cys29 was acylated by an electrophilic fragment of ligands with an interaction energy of −2 kcal/mol for 4c (Table 7). The acetyloxy portion in 4c was stabilized by an arrangement in parallel mode with His111 and Gly74, respectively (Fig. 9). In addition, 6b and 4c interacted with the same 1NJE amino acid backbone that interacted with the DCMP inhibitor (Fig. 10). 6b also interacted with the two H-bonds of Thr24 and Ala315 (Fig. 11).
| E (kcal/mol) | Distance (Å) | Interaction | Amino acid residues | Receptor | Atom | Ligand |
|---|---|---|---|---|---|---|
| PDB: 4uro | ||||||
| Reference drug | −6.2 | 3.79 | H-donor | ASP81 | OD2 | N1 |
| −2.3 | 3.64 | H-donor | ASN54 | O | O6 | |
| −5 | 3.63 | H-donor | ASP89 | OD1 | O3 | |
| −3.3 | 3.91 | H-acceptor | ARG144 | NH1 | O11 | |
| −1 | 3.66 | H-acceptor | ARG144 | NH2 | O11 | |
| 6b | −0.9 | 3.14 | H-donor | GLU58 | OE1 | O19 |
| −7.4 | 3.19 | H-acceptor | GLY125 | N | O10 | |
| −0.6 | 3.63 | H-acceptor | ASN54 | CB | O23 | |
| 4c | −1.5 | 2.97 | H-acceptor | THR173 | OG1 | O10 |
| −4.1 | 3.37 | H-acceptor | GLY125 | N | O22 | |
| −6.8 | 2.91 | H-acceptor | GLY125 | N | O23 | |
| −1.4 | 2.91 | H-acceptor | SER128 | OG | O23 | |
| PDB:1gmy | ||||||
| 6b | −1.5 | 3.09 | H-donor | GLU122 | OE2 | O17 |
| −0.8 | 3.6 | H-acceptor | GLN23 | NE2 | O21 | |
| 4c | −2 | 3.88 | H-donor | CYS29 | SG | N19 |
| −1.7 | 3.45 | H-acceptor | HIS111 | NE2 | O23 | |
| PDB:1NJE | ||||||
| DCMP | −3.2 | 3.29 | H-donor | ASN229 | OD1 | N3 |
| −0.7 | 3.07 | H-donor | TYR261 | OH | O3′ | |
| −1.5 | 2.7 | H-acceptor | ASP221 | N | O2 | |
| −2.1 | 2.99 | H-acceptor | SER219 | OG | O5′ | |
| −4 | 3.07 | ionic | ARG218 | NH1 | O2P | |
| −3.2 | 3.29 | H-donor | ASN229 | OD1 | N3 | |
| 6b | −9.1 | 2.37 | H-acceptor | THR24 | OG1 | O10 |
| −0.8 | 3.29 | H-acceptor | ALA315 | CB | O10 | |
| −0.5 | 2.64 | H-acceptor | HOH355 | O | O10 | |
| 4c | −3.3 | 2.95 | H-donor | HOH340 | O | N35 |
| −3.4 | 3.18 | H-acceptor | ARG23 | NH1 | O39 | |
| −3.4 | 3.98 | pi-H | HOH340 | O | 6-ring | |
The different interaction modes of the ligands with the hydrophilic amino acid backbone in both binding sites, 4uro and 1gmy (Figs. 6–11), provided evidence that hydrophobicity and membrane permeability are important pharmabiotic parameters for absorption molecules in biological systems.
3.3.1 In silico pharmacokinetic profile
Oral bioavailability is a critical feature in a therapeutic bioactive molecule. When investigating chemicals with potential use as drugs, a group of test categories referred to as ADMET (absorption, distribution, metabolism, excretion, and toxicity) is used to determine how the chemicals interact with the human body as a system. The ADMET factors prevent several imperative therapeutic agents used in the clinic trial field. Calculations were computed using MOE and the ADMET-SAR model. The results obtained are shown in Table 8. The ADMET properties of the synthesized compounds 6b and 4c were performed using calculated Lipinski rules (Lipinski et al., 2001), percent absorption (%ABS) (Zhao et al., 2002), and topological polar surface area (TPSA). These are linked to the drug bioavailability and showed that passively absorbed molecules with a TPSA > 140 possess low oral bioavailability (Clark and Pickett 2000). The tested compounds had values between 6 and 10 for H-bond acceptors and between 1 and 5 for H-bond donors, which indicates the high flexibility of these compounds. The ‘Clog P’ lipophilicity characters were lower than 5.0 (Clark and Pickett 2000). In agreement with Lipinski’s rule, the absorption percent was ∼68–70% for these compounds. The TPSA values (Table 8) showed that the synthesized compounds demonstrated good drug absorption against the different parameters depicted in Table 8. The carcinogenic behavior of the synthesized compounds was investigated by comparing them with 981 various carcinogenic chemical structures obtained from the Carcinogenic Potency Database (CPDB). Results displayed as zero had a carcinogenicity effectiveness within the range of values ∼ None and 0.8 mg/kg body wt/day. In general, the synthesized compounds demonstrated great bioavailability, possessing a high ability for BBB transport. Moreover, there were no noticeable health effects observed for the rodent toxicity profiles.
| Cpd. | 3 | 4 |
|---|---|---|
| HBD | 3 | 1 |
| HBA | 7 | 6 |
| Log.P | 2.42 | 2.98 |
| Log.S | −4.26 | −5.45 |
| V | 0 | 0 |
| TPSA | 112.93 | 85.19 |
| %ABS | 70.03 | 79.6 |
| Mutagenic | Low | None |
| Tumorigenic | High | High |
| Reproductive Effective | High | None |
| Irritant | High | None |
| Carcinogens | None | 0.8184 |
| Drug like | 3.4374 | −2.375 |
| HIA+ | 0.9893 | 0.9861 |
| Caco2- | 0.5734 | 0.5223 |
| BBB+ | 0.8989 | 0.9285 |
| Biodegradation | None | 0.7954 |
| AMES Toxicity | None | 0.5381 |
| Acute Oral Toxicity | None | 0.6191 |
HBD, number of hydrogen bond donor; HBA, number of hydrogen bond acceptor; Log P, calculated lipophilicity; Log S, solubility parameter; V, number of violation from Lipinski’s rule of five; TPSA, topological polar surface area (Å2); %ABS, absorption percentage; HIA+, human intestinal absorption; Caco2, Caco-2 permeability.
4 Conclusion
To test the efficacy of certain types of compounds as anti-cancer agents, we synthesized sugar hydrazones, arylidene derivatives, and oxadiazolines and then elucidated the chemical structures using spectroscopy analyses including IR, 1HNMR, and 13CNMR. The compounds synthesized were studied using molecular docking software to determine the active sites in their structures. Finally, the binding of DNA with cancer cells was carried out and the compounds were tested against a breast cancer cell line, which resulted in moderate to high inhibitory activity.
Declaration of Competing Interest
The authors declared that there is no conflict of interest.
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