A volume (25 mL) of dichloromethane–acetone (75:25, v/v) was added and the container
was vigorously homogenised in an ultrasounds bath for 10 min. Sodium chloride (3 g) and anhydrous sodium sulphate (12 g) were added followed by vigorous shaking for 5 min. After phase partitioning
(10 min, 4000 rpm) in a centrifuge, an aliquot of 15 mL of the organic layer was transferred to a 40 mL glass vial and evaporated to dryness under a stream of nitrogen in Turbo Vap LV evaporator
and the residue was redissolved in acetonitrile (2 mL).