Table 3.
Inhibitory zones (mm) induced by turmeric ethanol extracts and curcumin on bacteria.
| Bacterium | Material | Concentration (mg/mL) | ||||
|---|---|---|---|---|---|---|
| Gram (+) | B. subtilis | Extract | 50 mg/mL | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL |
| Non–roasted | 24.25 a* ± 0.14 | 21.29 a ± 0.57 | 17.73 a ± 1.10 | 8.41 a ± 0.75 | ||
| Light–roasted | 24.18 a ± 0.73 | 20.91 a ± 0.76 | 17.66 a ± 0.79 | 8.44 a ± 1.28 | ||
| Dark–roasted | 14.91 b ± 1.33 | 14.23 b ± 1.06 | 10.89 b ± 0.67 | 3.44 b ± 0.46 | ||
| Curcumin | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL | 3.13 mg/mL | ||
| 10.42 ± 0.70 | 7.80 ± 0.23 | 5.04 ± 0.64 | 3.07 ± 0.26 | |||
| S. aureus | Extract | 50 mg/mL | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL | |
| Non–roasted | 31.65 a* ± 1.09 | 25.89 a ± 0.16 | 14.85 a ± 0.72 | 10.06 a ± 0.90 | ||
| Light–roasted | 31.19 a ± 0.43 | 25.40 a ± 0.69 | 15.21 a ± 1.97 | 9.91 a ± 1.06 | ||
| Dark–roasted | 20.91 b ± 0.85 | 17.57 b ± 0.67 | 7.22 b ± 0.65 | 3.71 b ± 0.28 | ||
| Curcumin | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL | 3.13 mg/mL | ||
| 12.58 ± 1.39 | 9.64 ± 0.76 | 6.61 ± 1.09 | 3.06 ± 0.06 | |||
| Gram (−) | E. coli ATCC 25922 | Extract | 50 mg/mL | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL |
| Non–roasted | 20.36 a* ± 1.63 | 10.79 a ± 0.33 | 7.95 a ± 0.39 | 5.00 ± 0.91 | ||
| Light–roasted | 20.55 a ± 1.23 | 10.12 a ± 1.29 | 7.78 a ± 0.86 | 5.03 ± 1.16 | ||
| Dark–roasted | 14.34 b ± 0.69 | 7.39 b ± 0.85 | 4.70 b ± 0.47 | - | ||
| Curcumin | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL | 3.13 mg/mL | ||
| 7.99 ± 0.12 | 5.66 ± 0.78 | 3.74 ± 1.03 | - | |||
| E. coli ATCC 85922 | Extract | 50 mg/mL | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL | |
| Non–roasted | 16.78 a* ± 2.26 | 12.56 a ± 2.05 | 9.66 a ± 1.17 | 5.57 ± 0.79 | ||
| Light–roasted | 17.11 a ± 0.47 | 12.33 a ± 3.82 | 8.99 a ± 0.95 | 5.66 ± 1.84 | ||
| Dark–roasted | 11.68 b ± 0.33 | 7.66 b ± 0.84 | 5.25 b ± 0.58 | - | ||
| Curcumin | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL | 3.13 mg/mL | ||
| 7.81 ± 0.24 | 5.78 ± 0.58 | 3.45 ± 0.71 | - | |||
| P. aeruginosa | Extract | 50 mg/mL | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL | |
| Non–roasted | 12.51 a* ± 0.83 | 9.66 a ± 0.69 | 7.02 a ± 0.32 | 3.63 ± 0.13 | ||
| Light–roasted | 11.64 a ± 0.85 | 9.66 a ± 1.74 | 7.01 a ± 0.69 | 3.75 ± 0.52 | ||
| Dark–roasted | 9.79 b ± 0.34 | 7.46 b ± 0.47 | 4.05 b ± 0.27 | - | ||
| Curcumin | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL | 3.13 mg/mL | ||
| 7.77 ± 0.50 | 3.76 ± 0.52 | - | - | |||
| S. Typhimurium | Extract | 50 mg/mL | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL | |
| Non–roasted | 9.85 a* ± 0.42 | 7.30 a ± 0.52 | 6.27 ± 0.31 | 5.40 ± 0.45 | ||
| Light–roasted | 10.12 a ± 1.18 | 7.77 a ± 0.67 | 6.44 ± 0.68 | 5.17 ± 0.81 | ||
| Dark–roasted | 6.15 b ± 0.86 | 4.74 b ± 1.20 | - | - | ||
| Curcumin | 25 mg/mL | 12.5 mg/mL | 6.25 mg/mL | 3.13 mg/mL | ||
| 4.54 ± 0.56 | 3.07 ± 0.13 | - | - | |||
Results are expressed as means ± standard deviation (SD) of three tests. - means no inhibition. Values with different superscript letters indicate significant difference (p < 0.05) compared with other values from different extracts or compounds at similar concentrations on the same bacterium, assessed by one-way ANOVA followed with Tukey’s post hoc test. Values with superscripted * and bold letters indicate significant difference (p < 0.05) between the maximum inhibition zone induced by non-roasted turmeric vs. that of the curcumin, assessed by unpaired t-test. B. subtilis, Bacillus subtilis ATCC 6633; E. coli, Escherichia coli; S. aureus, Staphylococcus aureus ATCC 25923; S. Typhimurium, Salmonella Typhimurium ATCC 13311; P. aeruginosa, Pseudomonas aeruginosa ATCC 9027.