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Light-activated cytotoxicity studies on Co(II) complexes having tridentate anthraquinone-based ligands

Das, D and Sarma, N and Kausar Raza, M and Goswami, TK (2023) Light-activated cytotoxicity studies on Co(II) complexes having tridentate anthraquinone-based ligands. In: Inorganica Chimica Acta, 556 .

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Official URL: https://doi.org/10.1016/j.ica.2023.121622


Co(II) is a bioessential ion and its complexes are less prone to reduction by cellular thiols thereby reducing the probability of dark toxicity. Based on the above analogy, we have designed and synthesized five anthraquinone-based binary cobalt(II) complexes viz. [Co(HL1)2] (1), [Co(HL2)2] (2), [Co(HL3)2] (3), [Co(HL4)2] (4) and [Co(HL5)2] (5), where H2L1 = 2-(2-hydroxyphenyl)-1H-anthra[1,2-d]imidazole-6,11-dione; H2L2 = 2-(4-(diethylamino)-2-hydroxyphenyl)-1H-anthra[1,2-d]imidazole-6,11-dione; H2L3 = (2-(2-hydroxy-3-methoxyphenyl)-1H-anthra[1,2-d]imidazole-6,11-dione; H2L4 = 2-(3-hydroxy-6-(hydroxymethyl)-2-methylpyridin-4-yl)-1H anthra[1,2-d]imidazole-6,11 dione and H2L5 = 2-(3-hydroxynaphthalen-2-yl)-1H-anthra[1,2-d]imidazole-6,11-dione. The complexes were thoroughly characterized by spectroscopic and analytical methods and their potential application in photoactivated chemotherapy have been evaluated. The complexes 1–5 showed an irreversible voltammetric response at 0.43 V to 0.88 V corresponding to Co(II)/Co(III) couple. Three other responses were observed at ∼ -0.92 V, ∼ -1.16 V and ∼ -1.48 V for the ligands present in the binary Co(II) complexes due to quinone (Q)/ semiquinone (SQ[rad]-) and semiquinone (SQ[rad]-)/ catecholate (Cat2-) redox couples. The complexes display significant binding affinity to human serum albumin (HSA) displaying binding constants in the range 6.70 (±0.10) × 104 to 3.13 (±0.05) × 105 M−1. They also bind to calf-thymus (ct) DNA showing Kb values in the order ∼ 105-106 M−1. In vitro light-activated cytotoxicity studies showed significant photocytotoxicity against human cervical carcinoma, HeLa (IC50 ∼ 1.6–4.2 µM) and human lung carcinoma, A549 (IC50 ∼ 2.1–6.1 µM) cells with minimal dark toxicity (IC50 > 70 µM). Flow cytometric experiments reveal that complex 5 is able to produce reactive oxygen species (ROS) on exposure to visible light which responsible for photoactivated cytotoxicity.

Item Type: Journal Article
Publication: Inorganica Chimica Acta
Publisher: Elsevier B.V.
Additional Information: The copyright for this article belongs to the Elsevier B.V.
Keywords: Anthraquinone-based ligands; Co(II) complexes; HSA binding; Photocytotoxicity; ROS generation.
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 17 Jul 2023 10:52
Last Modified: 17 Jul 2023 10:52
URI: https://eprints.iisc.ac.in/id/eprint/82445

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