Table 1.
Regression coefficient (β), coefficient of determination (R2) and F-test value of the central composite design (CCD) model for alkaloids, polyphenolics and antioxidant activities.
| Alkaloids | Polyphenolics | Antioxidant activity | ||||
|---|---|---|---|---|---|---|
| Berberine | Palmatine | TP (mg GAE/g dw) | ABTS (mM AAE/g dw) | FRAP (mM AAE/g dw) | DPPH (mM AAE/g dw) | |
| Intercept, β0 | 17.17 | 8.45 | 12.74 | 11.83 | 134.83 | 34.51 |
| β1 | −0.56* | 0.26 | 0.45 | 1.94*** | 22.07*** | 2.14*** |
| β2 | 6.20*** | 3.26*** | 1.79*** | 0.99** | −1.35 | 10.20*** |
| β3 | −2.46*** | −1.06* | −0.44 | −0.38 | −7.98*** | 0.021 |
| β4 | 6.19*** | 2.16*** | 0.31 | 2.52*** | 29.50*** | 3.05*** |
| β12 | −1.99* | −0.17 | 3.24** | 2.16** | 11.79*** | 1.41 |
| β22 | 3.07*** | 0.48 | −1.03 | −1.01 | −10.48*** | −1.70 |
| β32 | 1.19 | 0.70 | 0.69 | −1.80* | 22.32*** | −1.17 |
| β42 | 3.62*** | 0.60 | −1.43 | 0.016 | −5.03* | −0.57 |
| β12 | 3.25*** | 1.19* | 0.61 | 0.93** | −0.54 | 1.28** |
| β13 | −2.64*** | −0.64 | −1.31** | 0.72* | −9.19*** | −0.14 |
| β14 | −1.02** | 0.12 | 0.90* | 0.68* | 13.71*** | 0.71 |
| β23 | −2.32*** | −0.86 | −0.32 | −0.53 | 0.32 | −0.65 |
| β24 | 4.32*** | 1.35** | 1.38** | 1.81*** | 6.40*** | 1.88*** |
| β34 | −0.29 | −0.52 | −0.22 | −0.087 | 8.13*** | −0.44 |
| R2 | 0.99 | 0.89 | 0.85 | 0.93 | 0.99 | 0.98 |
| F value (model) | 140.84*** | 8.82*** | 6.24*** | 16.17*** | 294.54*** | 75.88*** |
| F value (lack of fit) | 4.66 | 135.87 | 4.26 | 4.58 | 4.65 | 4.67 |
β1 = regression coefficient of microwave power, β2 = sample to solvent ratio, β3 = solvent pH, β4 = solvent concentration, TP = total phenols, ABTS = 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) radical cation inhibition, FRAP = Ferric reducing antioxidant power, DPPH = 2,2-diphenyl-1-picrylhydrazyl radical scavenging ability;AAE = ascorbic acid equivalent; GAE = gallic acid equivalent; dw = dry weight. Level of significance *p < 0.05, **p < 0.01, ***p < 0.001.