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. 2017 Feb 4;22(2):232. doi: 10.3390/molecules22020232

Figure 2.

Figure 2

Contour plots showing the effects of four variables (solvent concentration, material to liquid ratio, ultrasonic power, and extraction temperature) and their interactions on extraction efficiency of total phenols (TP, af) and their DPPH• scavenging capacity (gl). The other two variables in each of the Figures were kept constant at their respective central experimental values.