Synthesis, crystal structure and biological evaluation of three new Rh(III) complexes incorporating benzimidazole derivatives

Journal Pre-proofs Short communication Synthesis, crystal structure and biological evaluation of three new Rh(III) complexes incorporating benzimidazole derivatives Jun-Hong Liu, Feng-Hua Pan, Zhen-Feng Wang, Rong Wang, Lin Yang, Qi- Pin Qin, Ming-Xiong Tan PII: S1387-7003(20)30607-9 DOI: https://doi.org/10.1016/j.inoche.2020.108017 Reference: INOCHE 108017 To appear in: Inorganic Chemistry Communications Received Date: 11 May 2020 Revised Date: 6 June 2020 Accepted Date: 7 June 2020 Please cite this article as: J-H. Liu, F-H. Pan, Z-F. Wang, R. Wang, L. Yang, Q-P. Qin, M-X. Tan, Synthesis, crystal structure and biological evaluation of three new Rh(III) complexes incorporating benzimidazole derivatives, Inorganic Chemistry Communications (2020), doi: https://doi.org/10.1016/j.inoche.2020.108017 This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Elsevier B.V. All rights reserved. Synthesis, crystal structure and biological evaluation of three new Rh(III) complexes incorporating benzimidazole derivatives Jun-Hong Liu,a,1 Feng-Hua Pan,b,1 Zhen-Feng Wang,b Rong Wang,b,* Lin Yang,b Qi-Pin Qin,b,c,* Ming-Xiong Tanb,* a Baotou Iron ＆ Steel Vocational Technical College, Baotou 014010, Inner Monggol, PR China. b Guangxi Key Lab of Agricultural Resources Chemistry and Biotechnology, College of Chemistry and Food Science, Yulin Normal University, 1303 Jiaoyudong Road, Yulin 537000, PR China. rongwangjlu@126.com (R. Wang); qpqin2018@126.com (Q.-P. Qin); mxtan2018@126.com (M.- X. Tan). c State Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources, School of Chemistry and Pharmacy, Guangxi Normal University, 15 Yucai Road, Guilin 541004, PR China. 1 These authors contributed equally to this work. 1 Abstract Three new non-cisplatin analogs [Rh(BID1)(CH OH)]CH OH (Rh-1), [Rh(BID2)(CH OH)]CH OH 3 3 3 3 (Rh-2) and [Rh(BID3)(CH OH)]2CH OH (Rh-3) bearing benzimidazole derivatives (BID1−BID-3) 3 3 were first prepared as potential anti-tumor compounds. The Rh-3 complex with 8-fluoro group in BID-3 ligand exhibited potential antiproliferative activity against multidrug-resistant human lung adenocarcinoma A549/DDP and cisplatin-resistant human ovarian cancer SK-OV-3/DDP cells, at most 5.0 fold more potent than Rh-1, Rh-2 and cisplatin under the same conditions. Importantly, Rh-1−Rh-3 are more selective for A549/DDP cells versus human normal liver HL- 7702 cells. The Rh-2 and Rh-3 caused mitochondrial dysfunction was in the following order: Rh- 3 > Rh-2. The different biological behavior of Rh-1−Rh-3 may correlate with different 8- substituted groups in benzimidazole derivatives. Keywords: benzimidazole derivatives; Rh(III) complexes; cell apoptosis; mitochondrial dysfunction Some of platinum-based anti-cancer agents, such as cisplatin, oxaliplatin and carboplatin, are widely used to various types of cancer therapy [1−9]. Despite many advantages in clinical chemotherapy, however, these Pt drugs also showed strong resistance, serious adverse effects, and poor selectivity, etc [1−9]. Thus, to overcome these shortcomings of Pt-based agents, quite a number of non-Pt metal complexes have been explored [10−18]. As it is known that Rh(III) complexes display interesting antitumor, wide biological applications and antibacterial activities, which have a different mechanism of cisplatin and its ramification [19−30]. These complexes include 2,6-bis(2-benzimidazolyl)pyridine rhodium(III) derivative [19], 8-hydroxy-2- methylquinoline Rh(III) complex [20], 2(1H)-quinolinone Rh(III) complexes [21], RhIII(Cp*) and IrIII(Cp*) derivatives (Cp*= η5-pentamethylcyclopentadienyl) [22], 1H-imidazo[4,5- f][1,10]phenanthroline-based Rh(III) derivatives [23], pyridine-2-yl-2-phenyl cyclometallated Rh(III) complex [24], and piano-stool Rh(III) complex [26], etc. 2 Recently, a great deal of benzimidazole derivatives and their metal complexes have shown high anti-inflammatory, antiviral, antioxidant, antihistaminics, anti-proliferation, anti-ulcers, antifungals, anti-hypertensives, and antiparasitic activities [31−39]. For instance, a new type of 2-(2-pyridyl)benzimidazole cyclometalated Pt(II) complexes show high anticancer activity against SW480 cancer cells [32]. Mohapatra indicated that monocationic Cu(II) complexes can significantly inhibit NO release in vivo and in vitro [35]. In particular, a new family of Rh(III) complexes of benzimidazole derivatives have been tested as antiproliferative drugs in different cancer therapy [19−30]. Despite improvements in anticancer activity and tumor selectivity, the development of drug resistance and toxicity remains the major cause of cancer chemotherapy failure [31−39]. From this point of view, we report the first examples of three new non-cisplatin analogs [Rh(BID1)(CH OH)]CH OH (Rh-1), [Rh(BID2)(CH OH)]CH OH (Rh-2) and 3 3 3 3 [Rh(BID3)(CH OH)]2CH OH (Rh-3) derived from 3-(1H-Benzoimidazol-2-yl)-8-propenyl- 3 3 chromen-2-ylideneamine (BID1), 3-(1H-Benzoimidazol-2-yl)-8-tert-butyl-chromen-2- ylideneamine (BID2), 3-(1H-Benzoimidazol-2-yl)-8-fluoro-chromen-2-ylideneamine (BID-3) and RhCl 3H O, and investigate their anticancer activity against SK-OV-3/DDP and A549/DDP tumor 3 2 cells in vitro. The ligand 3-(1H-Benzoimidazol-2-yl)-8-propenyl-chromen-2-ylideneamine (BID1), 3-(1H- Benzoimidazol-2-yl)-8-tert-butyl-chromen-2-ylideneamine (BID2), 3-(1H-Benzoimidazol-2-yl)-8- fluoro-chromen-2-ylideneamine (BID3) was prepared as described previously [32,40,41]. In addition, the title [Rh(BID1)(CH OH)]CH OH (Rh-1), [Rh(BID2)(CH OH)]CH OH (Rh-2) and 3 3 3 3 [Rh(BID3)(CH OH)]2CH OH (Rh-3) were synthesized in high yield (70.5%−88.3%) by reaction of 3 3 RhCl 3H O with BID1, BID2 and BID3 in methanol and DMSO (v:v = 3.0mL:0.3mL) at reflux 3 2 temperature, respectively (Figure 1). 3 Figure 1. Synthetic route of benzimidazole complexes Rh-1−Rh-3. (a) piperidine (0.1 mL), CH CH OH (50.0 mL), 37℃, 6.0 h; (b) RhCl 3H O, methanol and DMSO (v:v = 3.0mL:0.3mL), 3 2 3 2 reflux, 12.0h. Air-stable red brown block crystals of Rh-1−Rh-3 were grown by methanol diffusion into a saturated solution of the Rh(III) complexes in DMSO. The crystal structure of Rh-1−Rh-3 (CCDC numbers: 2002790−2002792) were characterized successfully by the X-ray measurements. The details crystal data for Rh-1−Rh-3 have been reported in the Supporting Information (Table S1−S9). The ORTEP drawing of Rh-1−Rh-3 are shown in Figure 2. The RhIII center in Rh-1−Rh-3 adopts an approximately six-coordinated octahedral geometry and were surrounded by one BID1, BID2 or BID3 ligand (N^NH), three Cl ligands and one CH OH ligand. The bite angles of 3 N(1)–Rh(1)–N(3) were 88.42(12)°, 87.44(16)°, and 87.00(3)°, respectively. Figure 2. ORTEP drawing of Rh-1−Rh-3. The benzimidazole ligands (BID1, BID2, BID3) and their Rh(III) complexes Rh-1−Rh-3 were assayed for their anticancer activity in human SK-OV-3/DDP, A549/DDP cancer cells and normal HL-7702 cells (Table 1). The lack of cytotoxicity for the BID1, BID2, BID3 ligands were likely as previously demonstrated for 3-(1H-benzoimidazol-2-yl)-8-methylchromen-2-ylideneamine 4 (BMCY) and 3-(1H-benzoimidazol-2-yl)-8-fluoro-chromen-2-ylideneamine (BFCY) ligands [32]. In contrast, the Rh-1−Rh-3 showed high cytotoxic activity in the micromolar range (0.50−10.05μM), reflecting the central Rh(III) of Rh-1−Rh-3 in the coordinated mode with benzimidazole ligands were believed to play a key role in the high cytotoxicity (Table 1). The most potent derivatives was Rh-3 with IC value (0.50±0.12μM) against A549/DDP than that of 50 benzimidazole ligands (BID1, BID2, BID3), Rh(III) complexes Rh-1,Rh-2 and cisplatin. And the different antiproliferative activity for Rh-1−Rh-3 were in the following order: Rh-3 > Rh-2 > Rh-1 > cisplatin > BID-3 > BID1 and BID2. Comparing with BMCY and BFCY metal complexes (IC > 50 2.08±1.04μM) [32], Rh-3 exhibited stronger cytotoxicity against SK-OV-3/DDP and A549/DDP cancer cells, with IC values were 1.03±0.26 and 0.50±0.12μM, respectively. And as a result, 50 the existence of 8-fluoro substituents in Rh-3 could enhance its cytotoxicity, even at a lower concentration (0.50±0.12μM) than that of Rh-1 (7.11±1.86μM) and Rh-2 (3.21±0.49μM). Interestingly, Rh-1−Rh-3 also did not show obvious toxicity on the normal HL-7702 cells, which suggested their potential cytotoxic selectivity for A549/DDP. Table 1. The antiproliferative activity (μM) of Rh-1−Rh-3 against SK-OV-3/DDP, A549/DDP and HL-7702 cells for 24.0 h. compounds SK-OV-3/DDP A549/DDP HL-7702 BID3 97.26±1.02 86.09±1.24 >100 Rh-3 1.03±0.26 0.50±0.12 91.56±0.99 BID2 >100 >100 >100 Rh-2 5.49±0.57 3.21±0.49 86.26±1.80 BID1 >100 >100 >100 Rh-1 10.05±1.03 7.11±1.86 80.56±1.25 cisplatin 79.99±0.78 70.13±1.00 18.29±1.67 5 Cell apoptosis be identified as a kind of programmed cell death process [42−46]. Hence, the A549/DDP cells were treated with Rh-2 (3.21μM) and Rh-3 (0.50μM), and analyzed by flow cytometry (Figure 3). Obviously, treatment with Rh-2 (3.21μM) and Rh-3 (0.50μM), especially Rh-3 (0.50μM), enhanced the early (LR) and late apoptotic (UR) cell populations of the A549/DDP cells in comparison with untreated cells. When A549/DDP cells were incubated with Rh-2 (3.21μM) and Rh-3 (0.50μM), a total of 27.58% and 39.20% of apoptotic cells were in apoptosis phase (Figure 3), whereas the control group cells and cisplatin treated cells only were 6.89% and 13.33% [40,46], respectively. This suggested that cell death was induced by Rh-2 (3.21μM) and Rh-3 (0.50μM) via a high incidence of apoptosis. Figure 3. Apoptosis analysis of A549/DDP cells after 24 h of exposure to Rh-2 (3.21μM) and Rh- 3 (0.50μM) was measured by flow cytometry using PI vs. annexin V-FITC staining. Apoptosis was associated with the regulation of a mass of apoptosis-related proteins [45,46]. To study the mechanism of the apoptosis induced by RhIII complexes, the A549/DDP cells were treated with Rh-2 (3.21μM) and Rh-3 (0.50μM) for 24 h, and the expression of caspase-3/-9, bcl-2, cytochrome c (cyto C) and apaf-1 was assayed by western blot test. When the A549/DDP cells were treated with Rh-2 (3.21μM) and Rh-3 (0.50μM) for 24 h, the expression levels of caspase-3/-9, cytochrome c (cyto C) and apaf-1 were up-regulated, whereas the level of Bcl-2 anti-apoptotic protein was down-regulated (Figure 4). In contrast, less regulation of the five apoptosis-related protein levels in the tumor cells was observed when treated with cisplatin under the same conditions [40,46]. These results suggested that Rh-2 (3.21μM) and Rh-3 6 (0.50μM) could induce apoptosis in A549/DDP cells via the intrinsic pathway were in the following order: Rh-3 (0.50μM) > Rh-2 (3.21μM) > BMCY and BFCY metal complexes.[32] Figure 4. Western blot analysis of apoptosis-related proteins in A549/DDP cells treated with Rh- 2 (3.21μM) and Rh-3 (0.50μM) for 24 h. In conclusion, three benzimidazole derivatives Rh-1−Rh-3 have been synthesized and characterized by X-ray crystallography. Benzimidazole derivatives Rh-1−Rh-3 display promising anticancer activities toward A549/DDP and SK-OV-3/DDP cancer cells, at most 8.0 fold more potent than cisplatin. Interestingly, Rh-1−Rh-3 also did not show obvious toxicity on the normal HL-7702 cells. Most importantly, benzimidazole derivatives Rh-2 and Rh-3 could induce apoptosis in A549/DDP cells via mitochondrial dysfunction pathway. Acknowledgements This work was supported by the National Natural Science Foundation of China (Nos. 21867017 and 21761033) and the Natural Science Foundation of Guangxi (No. 2018GXNSFBA138021). 7 Appendix A. Supplementary material Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.inoche.2020.×××.×××. In addition, the CCDC numbers for benzimidazole derivatives Rh-1−Rh-3 were 2002790−2002792. References [1] F.-X. Wang, M.-H. Chen, Y.-N. Lin, H. Zhang, C.-P. Tan, L.-N. Ji, Z.-W. Mao, ACS Appl. Mater. Interfaces 9 (2017) 42471−42481. [2] Y. Han, X. Liu, Z. Tian, X. 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Chem. 124 (2016) 417–427. 11 Conflicts of interest ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Conflicts of interest There are no conflicts to declare. 12 Graphical abstract Synthesis, crystal structure and biological evaluation of three new Rh(III) complexes incorporating benzimidazole derivatives Jun-Hong Liu,a,1 Feng-Hua Pan,b,1 Zhen-Feng Wang,b Rong Wang,b,* Lin Yang,b Qi-Pin Qin,b,c,* Ming-Xiong Tanb,* Benzimidazole derivatives Rh-2 and Rh-3 could induce apoptosis in A549/DDP cells via mitochondrial dysfunction pathway. 13 Highlights: • Benzimidazole derivatives Rh-1−Rh-3 were synthesized and characterized. • Rh-1−Rh-3 are more selective for A549/DDP cells versus HL-7702 cells. • Rh-1−Rh-3 show high antitumor activity. • Rh-1−Rh-3 induce apoptosis via mitochondrial dysfunction pathway. 14