2.6.1. Standard Curve of Dencichine

The content of examined dencichine was determined by HPLC. Dencichine solution with concentration of 0, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16 mg/mL was prepared. The contents of dencichine at different concentrations were analyzed by HPLC (Agilent Technologies, La Jolla, CA, USA) at 213 nm. The standard curve is represented by the following fitting Equation (3).

$$\mathbf{A} = 4071.577 \mathbf{C} - 0.1569 \tag{3}$$

where A represents the absorption peak area of dencichine solution at 213 nm, C represents the concentration of the different dencichine standards (mg/mL) and the correlation coefficient (R2) for this equation was 0.9995.
