*2.4. Single-Factor Experimental Analysis of Extraction of Coumarins from A. dahurica* 2.4.1. Effect of Liquid–Solid Ratio

As shown in Figure 2, the extraction rates of different liquid–solid ratios (10, 20, 30, 40, 50 mL/g) were investigated under ultrasonic bath conditions (300 W, 50 Hz, 60 min, 60 ◦C) and 30% DES moisture content. When the liquid–solid ratio was 20:1, the extraction rate reached the highest value of 2.06%. When the liquid–solid ration continued to increase, the extraction rate showed a decreasing trend, because the increase in the liquid–solid ratio can make the system have higher solubility and promote the breakdown of cell walls, aiming to increase the overflow ratio of the content. However, when the solubility is large enough, there will be a saturation phenomenon, which would lead to some components not being dissolved, resulting in waste of extraction solvent and complexity of the extraction process, thus affecting the extraction effect.

**Figure 2.** Effect of liquid–solid ratio on the extraction yield of coumarins.
