Antioxidant activity of aminodiarylamines in the thieno[3,2-b]pyridine series: radical scavenging activity, lipid peroxidation inhibition and redox profile

Figures & data

Figure 1. Structures of the synthetic antioxidants edaravone and ebselen.

Figure 2. Structures of the precursor methyl 3-aminothieno[3,2-b]pyridine-2-carboxylate 1, of the nitrodi(hetero)arylamines 2 and of the corresponding aminodi(hetero)arylamines 3.

Figure 3. (A) Scavenging activity on DPPH radicals (RSA), (B) RP (Abs at 690 nm), (C) CLS and (D) TBARS assay using brain homogenized tissue for compounds 3a–c (3a ▴; 3b ▪; 3c •). Results are the mean ± SD of three independent experiments.

Table 1. EC₅₀ values^a (µM) obtained for the antioxidant activity of the diarylamines 3a–c and the standard trolox (mean ± SD; n = 3).

	3a	3b	3c	Trolox
RSA	131.51 ± 26.22	158.86 ± 9.33	62.62 ± 0.77	171.91 ± 6.84
RP	59.12 ± 0.39	295.15 ± 4.31	33.18 ± 2.85	118.35 ± 12.59
CLS	41.30 ± 3.44	196.15 ± 3.99	43.95 ± 2.78	10.52 ± 0.57
TBARS	7.27 ± 0.22	16.58 ± 0.40	11.97 ± 1.19	14.90 ± 7.60

^aResults are given in concentrations providing 50% of antioxidant activity in RSA, CLS and TBARS assays, and 0.5 of absorbance in RP assay.

Figure 4. Electrochemical responses for 1 mM nitrodi(hetero)arylamines 2, the corresponding aminodi(hetero)arylamines 3 and trolox in 0.1 M TBAP/CH₃CN solutions, with Pt electrodes: (left) cyclic voltammogram at 0.1 Vs⁻¹ between −0.5 and 1.2/1.5 V; (right) differential pulse voltammogram obtained with 0.06 V pulse amplitude at 0.02 V.s⁻¹.

Figure 5. Cyclic voltammograms of 1 mM aminodi(hetero)arylamine 3a in 0.1 M TBAP/CH₃CN solution, with Pt electrodes, between −0.5 and 1.2 V at 0.1 Vs⁻¹: (A) first scan; (B) after several scans.

Table 2. Peak potentials obtained for the electrochemical oxidation processes (CV and DPV) of the nitrodi(hetero)arylamines 2, the corresponding aminodi(hetero)arylamines 3, and the standard trolox.

	CV (V)			DPV (V)			EAP
	Ep1	Ep2	Ep3	Ep1	Ep2	Ep3	p1	p2	p3	Total EAP
2a	–	1.32 ± 0.01	>1.60	–	1.24 ± 0.07	1.39 ± 0.07	–	0.30 ± 0.00	0.01 ± 0.0	0.31 ± 0.00
2b	–	1.35 ± 0.00	>1.60	–	1.27 ± 0.07	>1.60	–	0.33 ± 0.02	>1.60	0.33 ± 0.02
2c	–	1.19 ± 0.02	1.42 ± 0.01	–	1.12 ± 0.02	1.38 ± 0.00	–	0.40 ± 0.00	0.19 ± 0.02	0.59 ± 0.02
3a	0.49 ± 0.00	0.79 ± 0.00	1.10 ± 0.02	0.43 ± 0.00	0.77 ± 0.01	1.05 ± 0.01	0.71 ± 0.01	0.29 ± 0.01	0.23 ± 0.01	1.23 ± 0.01
3b	–	0.76 ± 0.01	0.94 ± 0.01	–	0.71 ± 0.00	0.90 ± 0.00	–	0.14 ± 0.01	0.31 ± 0.00	0.45 ± 0.01
3c	–	0.63 ± 0.02	0.81 ± 0.01	–	0.55 ± 0.02	0.74 ± 0.01	–	0.38 ± 0.02	0.46 ± 0.01	0.84 ± 0.02
Trolox	0.94 ± 0.01	–	–	0.81 ± 0.00	–	–	–	–	–	–

Electrochemical Antioxidant Power (EAP) expressed in mM of trolox equivalents per mM of diarylamine (mean ± SD; n = 3).

Figure 6. Variation of the oxidation peak height for different trolox concentration (0.05–2 mM), obtained by DPV of trolox/TBAP/CH₃CN solutions, with Pt electrodes between −0.5 and 1.2 V, with 0.06 V pulse amplitude at 0.02 Vs⁻¹.