Instrumentation and analytical condition.
Validated HPLC method [34] was performed on a Shimadzu SCL-10A HPLC system, equipped with a model LC-10AD pump, UV–vis detector SPD-10A, Rheodyne injector fitted with a 20 μL loop and auto injector SIL-10A. A Hypersil® BDS C18 column (250×4.6 mm, 5 μm particle size) with a C18 guard column was used. The elution was carried out with gradient solvent.