EXPERIMENTAL
Plantmaterials
Mangosteen bark, leaves and fruit pericarp collected from an
orchard in Songkhla province, Thailand, in April 2009 were rinsed
with water to remove soil. The tissues were cut into pieces (0.5–1.0
cm2), dried overnight in a tray dryer at 45 ◦C and ground to yield
material of approximately 18 mesh.
Preparation of extracts inmethanol
Ground materials were extracted six times with 80% methanol as
described by Zadernowski et al.5 The recovered supernatants were
passed through filter paper (Whatman No. 4) to remove remaining
bulk impurities before lyophilization at 30 ◦C. Dried extracts were
stored in the dark at 4 ◦C until used.
Optimization of phenolic extraction in hot water
Extraction of phenolics from all tissues with hot water was
optimized using response surface methodology as described by
Haaland.17 A two-factor five-level central composite experimental
design was used consisting of nine runs including the independent
variables temperature and water:solid ratio (Table 1). Extraction
time was fixed at 30 min to minimize thermal degradation of
phenolic compounds during extraction.