2.2. Preparation of water-soluble extract
Soluble materials were extracted by incubating 1.0 g of the
dried powder with 15 ml distilled water for 20 min at 80 C. Then
the suspension was centrifuged for 5 min at 3000 rpm using a
swing rotor (TS-7; Tomy, Tokyo, Japan) followed by filtration and
the supernatant was recovered. Distilled water was added to the
residue and the extraction procedure was repeated. The two supernatant
fractions were combined and made up to a volume of 50 ml.