TABLE 3.
Regression coefficient (β) and fit statistics of the predicted second‐order polynomial models for flavonoids and antioxidant activity
| Factor | Coefficient (β) | ||
|---|---|---|---|
| TFC | DPPH | OH− | |
| F value (model) | 25.83 *** | 9.84 *** | 7.44 *** |
| F value (lack of fit) | 1.19 | 2.64 | 2.19 |
| Intercept | 5.70 | 79.61 | 16.85 |
| X 1 | −0.73 *** | −0.84 | −10.44 *** |
| X 2 | 2.06 *** | −1.91 ** | 6.30 *** |
| X 3 | 0.61 *** | −4.42 *** | 2.09 |
| X 4 | 0.46 ** | 2.36 ** | 0.27 |
| X 1 X 2 | −0.19 | 1.86 | −2.66 |
| X 1 X 3 | 0.30 | 5.44 *** | −4.88 |
| X 1 X 4 | 0.46 * | −4.02 ** | 5.99 * |
| X 2 X 3 | 1.14 *** | −5.92 *** | 1.17 |
| X 2 X 4 | 0.47 | 1.34 | −1.98 |
| X 3 X 4 | 0.74 ** | 1.09 | 4.56 |
| X 1 2 | −0.97 *** | −1.83 | −0.64 |
| X 2 2 | 0.44 * | 1.43 | −1.92 |
| X 3 2 | 0.22 | −0.46 | −2.79 |
| X 4 2 | −0.72 ** | −0.16 | 6.71 ** |
| R 2 | .9627 | .9078 | .8816 |
| Adj. R 2 | .9255 | .8155 | .7631 |
| p‐value (lack of fit) | .4701 | .1815 | .2344 |
| p‐value (model) | <.0001 | <.0001 | .0003 |
Note: X 1: ethanol concentration (%); X 2: solvent‐to‐material ratio (ml/g); X 3: ultrasonic time (min); X 4: ultrasonic power (W).
Abbreviations: TFC, total flavonoids content; OH−, hydroxyl radical scavenging ability by the salicylic acid method; DPPH, 2‐2‐dipheny‐1‐picrylhydrazyl radical scavenging capacity.
*
p < .05: indicates significant level.
**
p < .01: indicates highly significant level.
***
p < .001: indicates remarkably significant level.