2. Materials and methods
2.1. Preparation of extracts
Lyophilized peels and seeds of Nephelium lappaceum L.
were powdered and then extracted with ether (three times).
The residue was then extracted with methanol (three times)
and finally with water (three times). After filtration, the combined
ether and methanolic extracts were evaporated under
vacuum to absolute dryness and the aqueous extract was
lyophilized.
2.2. Determination of the total phenolic contents
The amounts of phenolic compounds in the extracts were
determined according to the method of Waterman and Mole
(1994) using FolineCiocalteu method and catechin was used
as the standard phenolic compound. The extract solution in appropriate
solvent (0.1 mL) was transferred to a volumetric
flask containing 7.9 mL of distilled water. After that, 0.5 mL
of FolineCiocalteu reagent was added. Three minutes later,
1.5 mL of 200 g/L sodium carbonate solution was added. Subsequently,
the shaken mixture was allowed to stand for 2 h at
room temperature and then measured at 760 nm. The experiment
was carried out in triplicate and the total phenolic compounds
were expressed as catechin equivalents.