RESUMO
Echinacea purpurea is a traditional medicinal plant widely used as adjuvant for the treatment of respiratory and urinary infections. Caffeic acid derivatives are considered the main active markers, such as chicoric acid, caftaric acid and chlorogenic acid. An analytical method using ultra performance liquid chromatography (UPLC) and diode array detector was developed and validated, to quantify caffeic acid derivatives in commercial dried extracts of EP. UPLC method was developed using a C18 column (50 × 2.1 mm, 1.8 µm), at 30°C. Mobile phase was composed of acetonitrile and 0.05% (v/v) formic acid aqueous solution (10:90), flow rate 0.2 mL/min. Injection volume was 10 µL and detection was performed at 300 and 330 nm. The developed method complied with all required validation parameters, and showed to be linear, precise, accurate, selective and robust for all caffeic acid derivatives. Using the validated method, the levels of caftaric acid (0.110-0.507%w/w), chicoric acid (0.040-0.179%w/w) and chlorogenic acid (0.013-0.084%w/w) were determined in five commercial dried extracts of E. purpurea, with significant variation in the contents between different samples, indicating the need of standardization and control of individual caffeic acid derivatives in commercial extracts.