Table 1.
The coded values and corresponding actual values of the optimisation parameters.
| Code | Solvent concentration (%) | Ultrasonic time (min) | Liquid-solid ratio (mL · g-1) |
|---|---|---|---|
| −1 | 60 | 30 | 15 |
| 0 | 70 | 45 | 20 |
| 1 | 80 | 60 | 25 |
Figure 1.
The effect of different ultrasonic temperature (A), ultrasonic power (B), ultrasonic time (C), solvent concentration (D) and liquid–solid ratio (E) on the extraction yield of MELTF.
Table 2.
The coded experimental and predicted values for RSM design using ethanol as solvent.
| Run | X1 | X2 | X3 | Extraction yield (mg · g−1) | |
|---|---|---|---|---|---|
| Experimental | Predicted | ||||
| 1 | −1 | −1 | 0 | 5.71 | 5.29 |
| 2 | 0 | 1 | 1 | 8.33 | 8.26 |
| 3 | 0 | 0 | 0 | 7.42 | 8.00 |
| 4 | 0 | 1 | −1 | 6.85 | 6.62 |
| 5 | 0 | −1 | −1 | 5.71 | 5.79 |
| 6 | 1 | −1 | 0 | 6.53 | 6.64 |
| 7 | 0 | 0 | 0 | 7.74 | 8.00 |
| 8 | 0 | 0 | 0 | 8.30 | 8.00 |
| 9 | 1 | 0 | −1 | 7.62 | 7.43 |
| 10 | −1 | 0 | −1 | 4.39 | 4.73 |
| 11 | 0 | 0 | 0 | 8.38 | 8.00 |
| 12 | 0 | −1 | 1 | 6.43 | 6.65 |
| 13 | −1 | 0 | 1 | 6.63 | 6.83 |
| 14 | −1 | 1 | 0 | 6.11 | 6.00 |
| 15 | 1 | 1 | 0 | 7.95 | 8.37 |
| 16 | 1 | 0 | 1 | 8.17 | 7.83 |
| 17 | 0 | 0 | 0 | 8.14 | 8.00 |
Table 3.
Analysis of variance (ANOVA) for the effects of solvent concentration (X1), ultrasonic time (X2) and liquid-solid ratio (X3) on extraction yield of MELTF with ethanol as solvent using predicted polynomial models.
| Source | Sum of squares | Df | Mean square | F-value | p-value | Significanta |
|---|---|---|---|---|---|---|
| Model | 20.16 | 9 | 2.24 | 10.82 | 0.0024 | |
| X1 | 6.88 | 1 | 6.88 | 33.24 | 0.0007 | |
| X2 | 2.97 | 1 | 2.97 | 14.36 | 0.0068 | ** |
| X3 | 3.13 | 1 | 3.13 | 15.11 | 0.0060 | *** |
| X1X2 | 0.26 | 1 | 0.26 | 1.26 | 0.2987 | ** |
| X1X3 | 0.72 | 1 | 0.72 | 3.49 | 0.1038 | ** |
| X2X3 | 0.15 | 1 | 0.15 | 0.71 | 0.4273 | * |
| X12 | 2.53 | 1 | 2.53 | 12.23 | 0.0100 | * |
| X22 | 1.77 | 1 | 1.77 | 8.53 | 0.0223 | |
| X32 | 1.14 | 1 | 1.14 | 5.49 | 0.0516 | |
| Residual | 1.45 | 7 | 0.21 | |||
| Lack of fit | 0.79 | 3 | 0.26 | 1.58 | 0.3255 | Not significant |
| Pure Error | 0.66 | |||||
| Cor total | 21.61 | 4 | ||||
| R2 | 0.9329 | 16 | ||||
| R2adj. | 0.8467 |
Figure 2.
Response surface (3D) plots showing the effect of solvent concentration and ultrasonic time (A), solvent concentration and liquid–solid ratio (B), and ultrasonic time and liquid–solid ratio (C) on extraction yield of MELTF.
Figure 3.
Contour plot showing the effect of solvent concentration and ultrasonic time (A), solvent concentration and liquid–solid ratio (B), and ultrasonic time and liquid–solid ratio (C) on extraction yield of MELTF.
Table 4.
Result of model validation experiments.
| No. | Optimum conditions | Extraction yield (mg · g−1) | |||
|---|---|---|---|---|---|
| Solvent concentration (%) | Ultrasonic time (min) | Liquid-solid radio (mL · g−1) | Experimental | Predicted | |
| 1 | 76 | 55 | 22 | 8.79 | 8.62 |
| 2 | 76 | 55 | 22 | 8.28 | 8.62 |
| 3 | 76 | 55 | 22 | 8.39 | 8.62 |
| 4 | 76 | 55 | 22 | 8.56 | 8.62 |
| 5 | 76 | 55 | 22 | 8.93 | 8.62 |
| Average | 8.59 | ||||
| Ethanol leaching extraction | |||||
| 6 | 0 | 20 | 20 | 3.38 | |
| 7 | 0 | 20 | 20 | 3.28 | |
| 8 | 0 | 20 | 20 | 3.42 | |
| Average | 3.36 | ||||
Figure 4.
Elution profile of MELPTF on AB-8 macroporous resin column. MELPTF, MELTF after purification.
Figure 5.
α-Glucosidase inhibitory activities of MELTF and MELPTF. MELTF, M. exotica leaves total flavonoids; MELPTF, MELTF after purification.
Figure 6.
α-Amalyse inhibitory activities of MELTF and MELPTF. MELTF, M. exotica leaves total flavonoids; MELPTF, MELTF after purification.
Figure 7.
DPPH-scavenging activities of MELTF and MELPTF. DPPH, 1,1-diphenyl-2-picrylhdrazyl; MELTF, M. exotica leaves total flavonoids; MELPTF, MELTF after purification; VC, vitamin C.
Figure 8.
ABTS·+ scavenging activities of MELTF and MELPTF. ABTS, 2,2′-Azino-bis (3-ethylbenzthiazoline-6-sulphonic acid); MELTF, M. exotica leaves total flavonoids; MELPTF, MELTF after purification; VC, vitamin C.