Table 1.

Metal-centered reduction potential E_½ versus NHE (for MnIIIP/MnIIP redox couple), log kcat(O⁻) for the catalysis of O⁻ dismutation, log k_red(ONOO^–) for the 1-electron reduction of ONOO^– to ·NO₂ and the lipophilicity of Mn porphyrin-based SOD mimics expressed in terms of partition between n-octanol and water, log P_OW

Redox-active compounds	E½/mV vs. NHE	log kcat(O−)	log kred(ONOO–)	log POW
Mn porphyrins
MnTM-2-PyP5+	+220	7.79	7.28	−8.16a
MnTE-2-PyP5+	+228	7.76 (cyt. c), 7.73 (p.r.)c	7.53	−7.79a
MnTnBu-2-PyP5+	+254	7.25	7.11	−6.19b
MnTnHex-2-PyP5+	+314	7.48	7.11	−3.84b
MnTnHep-2-PyP5+	+342	7.65		−3.18b
MnTnOct-2-PyP5+	+367	7.71	7.15	−2.32b
MnTMOE-2-PyP5+	+251	8.04 (p.r.)	7.36	−7.52a
MnTMOHex-3-PyP5+	+68	6.78		−5.45b
MnTnBuOE-2-PyP5+	+277	7.83		−4.10b
MnBr8TM-3-PyP4+	+468	>8.85
MnTCl5TE-2-PyP4+	+560	8.41
MnTDE-2-ImP5+	+346	7.83 (p.r.)	7.43
MnTTEG-2-ImP5+	+412	8.55
MnMImPh3P2+		6.92		4.78
[MnBV2–]2	+460c	7.4
[MnBVDME]2	+450c	7.7
[MnMBVDME]2	+440c	7.36
[MnBVDT2–]2	+470c	7.4
MnTBAP3–	−194	3.16	5.02
MnTCHP+	−200 to −400		5–6 [44]
Fe porphyrins
FeTM-2-PyP5+	+212	7.95
FeTE-2-PyP5+	+215	8.00
FP15		>8d	6.80 [116]
cis-FeTM-4-Py2P2P3+		7 [188]
INO-4885			7.7 [189]
Mn salens
EUK-8	−130	5.78 (cyt. c) [190]
EUK-134	~−130	5.78
EUK-189	~−130	5.78		−0.90 [113]
EUK-207	~−130	IC50 = 0.48 μM (NBT assay)		−1.41 [113]
EUK-418		IC50 = 1.73 μM (NBT assay)		0.548 [113]
Cyclic polyamine
M40403	+525 (ACN), +840 (water)	7.08
Nitroxides
Tempol	+810c	<3 (pH 7.8)
Tempone	+918c	<3 (pH 7.8)
4-Carboxy-tempo		7.54 (pH 5.4)
Mn corroles
MnTrM-2-corrole3+	+910e	5.94
MnTrM-3-corrole3+	+880e	6.34
MnTrM-4-corrole3+	+760e	6.27
MnTrF5P-β(SO3)2-corrole2–	+840e	5.68
Metals, metal ions and oxides
OsO4		9.14 (pH 5.1–8.7) [12]
CeO2 (3- to 5-nm particles)		9.55 [11]
Nano-Pt		IC50 = 48.9 μM (7.7 WST-1 assay) [13]
Mn2+	+850f	6.11 (cyt. c), 6.28 (p.r.)
Metallotexaphyrin
Gd(III) texaphyrin (XCYTRINTM)	−41g [53]
Natural compounds (polyphenols)
Curcumin		IC50 = 115 μM (NBT assay) [191]
Honokiol		5.5 [192]
MitoQ	−105 (MitoQ/UQH·), water	8.30 kox(O−)		3.44 (37° C, n-octanol/PBS)
SOD enzymes	~+300	8.84–9.30	3.97

For comparison, the values for some other compounds listed in figures 1 and 2 are given also. In the absence of SOD enzyme, O⁻ self-dismutes at pH 7.8 with a rate constant of k(O⁻ self-dismutation) approximately 5 × 10⁵ M⁻¹ s⁻¹. Therefore, the compounds cannot be SOD mimics, if they disproportionate O⁻ with a rate constant equal to or lower than 5 × 10⁵ M⁻¹ s⁻¹ [log k(O⁻) ≤5.7]. cyt. = Cytochrome; p.r. = pulse radiolysis; IC₅₀ = 50% inhibitory concentration; NBT = nitroblue tetrazolium; ACN = acetonitrile; MitoQ = mitochondria-targeted ubiquinone; UQH· = ubisemiquinone; PBS = phosphate-buffered saline. E_½ is determined in 0.05 M phosphate buffer (pH 7.8, 0.1 M NaCl); k_cat was determined by cytochrome c assay in 0.05 M potassium phosphate buffer (pH 7.8, at 25 ± 1° C); for detailed comparison of validity of cytochrome c vs. NBT assay for k_cat determination, see Batinic-Haberle et al. [193].

^aData obtained from the relationship Rf vs. log P_OW (log P_OW = 12.207 × Rf – 8.521) [9, 68], and direct determinations of log P_OW for Mn(III) N-alkoxyalkylpyridylporphyrins; an error was made in the calculation of log P_OW values and is corrected herein.

^bDetermined experimentally using n-butanol and water biphasic system and converted to log P_OW according to the equation log P_OW = 1.55 × P_BW – 0.54; P_BW is the partition between n-butanol and water [68, 194].

^cThe 1-electron reduction potential refers to the RNO⁺/RNO· redox couple.

^dEstimated based on the determined k_cat(O⁻) for MnTTEG-2-PyP⁵⁺ [7, 8] and the relationship between the k_cat(O⁻) for FePs and MnPs [25].

^eE_½ data associated with the Mn^IV/Mn^III reduction potential in mV vs. Ag/AgCl [46].

^fOxidation potential only, Mn^III/Mn^II redox couple is irreversible.

^gReduction potential only, in N,N-dimethylformamide. When references are not indicated, the data are taken from Batinic-Haberle et al. [6,7,8].