Preparation of plant extracts
The preparations of plant materials used in this experiment
were described by Tewtrakul et al. (2003). Briefly, the
plants were collected in the area of Songkhla Province,
Thailand, with voucher specimens deposited at the herbarium
of the Faculty of Pharmaceutical Sciences, Prince
of Songkla University, Thailand. Dried plants were successively
extracted with chloroform, methanol and boiling
water. The solvents were removed under reduced pressure.
Each dried extract was dissolved, at a concentration of
100 mg/ml, in dimethyl sulphoxide (DMSO) before assay.
The extracts were further diluted with culture medium to a
concentration of 2 mg/ml. The maximum concentration of
DMSO in the test did not exceed 1%, at which level no
inhibition of amoeba growth occurred.