Characterization and Quantification of Luteolin-Metal Complexes in Aqueous Extract of Lonicerae Japonicae Flos and Huangshan Wild Chrysanthemum

Figure 2

Effect of reaction temperature on luteolin-metal complex formation. Luteolin (0.1 mmol) was mixed with 0.02 mmol anhydrous calcium chloride, anhydrous zinc chloride, magnesium chloride hexahydrate, iron chloride hexahydrate, or copper chloride dihydrate in 40 mL distilled water. The reaction was allowed to proceed for 4 h under heat backflow at a temperature of 30°C, 50°C, 70°C, or 90°C. After free ion salts were removed, the reactants were analyzed by HPLC as described in methods. The experiment was performed at least three times independently.