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 systems which were consisted of 0.1% v/v ortho phosphoric acid (solvent A) and acetonitrile (solvent B) with a flow rate of 1 mL/min at ambient temperature. The gradient programme was as follows: 70% B for 0–15 min, 70% B to 75% B in 3 min, 75% B to 80% B in 1 min, constant at 80% B for 6 min, 80% B to 70% B in 1 min. There was 11 min of post-run for reconditioning. The wavelength of the UV–vis detector was set at 320 nm. The compound was quantified using CLASS VP software. The content of α-mangostin was calculated using its calibration curve with regarding to the dilution factor and were expressed as gram per 100g of the extract.