High - performance liquid chromatography Shimadzu HPLC (Model SPD - 10A UV- VIS Detector) with a YMC- pack ODS - A, C18 column (250 × 4.6 mm; particle S - 5mm, 120
A). The linear gradient elution profile started with water:acetonitrile (75:25) and ended with water - acetonitrile (50:50) within 30min.