Table 1. IC50, MIC, ΣFICs, and Activity Indices (AI) of S. miltiorrhiza extracts in combination with cryptotanshinone.
IC50 and MICs represent concentrations of individual extracts required to inhibit bacterial growth (USA300 LAC AH1263)39 by 50 or 100%, and ΣFICs indicate the interaction between extracts and cryptotanshinone.
| IC50
(μg mL−1) |
MIC (μg mL−1) |
ΣFIC † | AI ‡ | |
|---|---|---|---|---|
| SM-1 | 12.9 ± 1.7 | ≤ 25 | 0.38, synergy | -- |
| SM-3 | 9.8 ± 1.5 | ≤ 25 | 0.19, synergy | -- |
| SM-5 | 11.4 ± 1.5 | ≤ 25 | 0.75, additivity | -- |
| SM-3-2 | > 100 | > 100 | 0.26, synergy | -- |
| SM-3-3 | > 100 | > 100 | 0.40, synergy | -- |
| SM-3-4 | 46.0 ± 7.2 | ≤ 100 | 0.14, synergy | -- |
| SM-3-2-1 | > 100 | > 100 | 0.31, synergy | 153 |
| SM-3-2-7 | > 100 | > 100 | 1.25, indifference | 42 |
| SM-3-2-8 | > 100 | > 100 | 0.38, synergy | 128 |
| SM-3-2-9 | > 100 | > 100 | 0.38, synergy | 151 |
| SM-3-3-2 | > 100 | > 100 | 2.0, indifference | 70 |
| SM-3-4-1 | > 100 | > 100 | 2.0, indifference | 67 |
| SM-3-4-2 | > 100 | > 100 | 2.0, indifference | 71 |
| SM-3-4-3 | > 100 | > 100 | 0.75, additivity | 113 |
| SM-3-4-4 | > 100 | > 100 | < 1.0, additivity § | 127 |
| SM-3-4-5 | 12.3 ± 6.3 | ≤ 25 | 0.60, additivity | 153 |
*
± standard error
†
ΣFICs were calculated using equation 2.
‡
Activity indices were calculated for third stage fractions only.
§
the highest concentration tested was 100 μg mL−1, which did not reach IC50. To conservatively estimate activity, 100 μg mL−1 was chosen as the IC50 of SM-3-4-4 to calculate the ΣFIC and yielded a result of 1.0. However, since the actual IC50 of SM-3-4-4 is higher than 100, the ΣFIC is lower than 1.0, categorized as additive.