Synchronized 3D7 P. falciparum was exposed to G. mangostana
Linn. extract at IC50 for 12 h. After incubation, culture medium
(1 ml) was added to ice-cold methanol:acetonitrile:water (3 ml,
40:40:20%, v:v:v) to quench the secreted metabolites. The
extracted medium was spiked with internal standards (b-alanine
and DL-arabinose for the positive and negative modes, respectively).
The quenched samples were centrifuged and supernatant
transferred into a new glass tube and dried under nitrogen flow
to concentrate the analytes. The dried samples were kept at
80 C until use.