Table 1.
The IC50 values of five di-COQs in various antioxidant assays.
| Compounds | PTIO•-Scavenging (pH 4.5, mg/mL, mM) | PTIO• Scavenging (pH 7.4, mg/mL, mM) | FRAP (μg/mL, μM) | DPPH•-Scavenging (μg/mL, μM) | ABTS+•-Scavenging (μg/mL, μM) |
|---|---|---|---|---|---|
| 1,3-COQ | 47.2 ± 1.6 | 57.7 ± 1.0 | 3.4 ± 0.2 | 2.9 ± 0.1 | 3.6 ± 0.0 |
| (91.4 ± 3.6 e) | (111.8 ± 2.0 c) | (6.5 ± 0.4 c) | (5.7 ± 0.3 b) | (6.9 ± 0.1 c) | |
| 1,5-COQ | 35.5 ± 2.8 | 63.0 ± 7.6 | 3.3 ± 0.1 | 4.7 ± 0.6 | 3.5 ± 0.0 |
| (68.7 ± 5.4 d) | (121.9 ± 14.8 c) | (6.4 ± 0.2 c) | (9.2 ± 1.1 c) | (6.7 ± 0.1 c) | |
| 3,4-COQ | 19.1 ± 0.4 | 22.3 ± 6.2 | 2.6 ± 0.1 | 2.9 ± 0.5 | 3.2 ± 0.0 |
| (37.0 ± 0.5 c) | (43.1 ± 12.0 b) | (5.1 ± 0.2 b) | (5.7 ± 0.9 b) | (6.2 ± 0.1 b) | |
| 3,5-COQ | 55.9 ± 2.6 | 60.2 ± 2590 | 3.4 ± 0.0 | 3.2 ± 0.5 | 3.6 ± 0.1 |
| (108.0 ± 5.1 f) | (116.5 ± 5.0 c) | (6.7 ± 0.1 c) | (6.1 ± 0.9 b) | (7.0 ± 0.3 c) | |
| 4,5-COQ | 4.3 ± 0.3 | 23.3 ± 0.3 | 2.6 ± 0.1 | 1.7 ± 0.9 | 2.8 ± 0.0 |
| (8.3 ± 0.3 b) | (45.2 ± 0.6 b) | (3.4 ± 2.9 a) | (3.4 ± 1.8 a) | (5.4 ± 0.1 a) | |
| Trolox | 33.4 ± 0.5 | 26.8 ± 1.5 | 16.4 ± 2.9 | 6.2 ± 0.0 | 6.9 ± 0.1 |
| (0.1 ± 0.0 a) | (0.1 ± 0.0 a) | (31.7 ± 5.5 d) | (12.0 ± 0.1 d) | (13.4 ± 0.2 d) |
The IC50 value (in μg/mL unit) was defined as the final concentration of 50% radical inhibition or relative reducing power, calculated by linear regression analysis, and expressed as the mean ± SD (n = 3). The linear regression was analyzed by Origin 6.0 professional software. The IC50 value was also expressed in μM/mM unit. The IC50 value in the μM/mM unit, with different superscripts (a, b, c, d, e, or f) in the same diagram, are significantly different (p < 0.05). Trolox is the positive control. 1,3-COQ: 1,3-di-O-caffeoylquinic acid; 1,5-COQ: 1,5-di-O-caffeoylquinic acid; 3,4-COQ: 3,4-di-O-caffeoylquinic acid; 3,5-COQ: 3,5-di-O-caffeoylquinic acid; 4,5-COQ: 4,5-di-O-caffeoylquinic acid. The dose-response curves are listed in Figure S1.