Abstract The anti-amoebic activities of chloroform, methanol
and water extracts from 12 Thai medicinal plants (39
extracts) commonly used by AIDS patients in southern
Thailand were screened, at a concentration of 1,000 μg/ml,
against Entamoeba histolytica strain HTH-56:MUTM and
strain HM1:IMSS growing in vitro. The extracts were
incubated with 2×105E. histolytica trophozoites/ml of medium
at 37°C under anaerobic conditions for 24 h. The
cultures were examined with an inverted microscope and
scored (1–4) according to the appearance and numbers of the
trophozoites. The extracts that caused inhibition were
selected and retested using the same conditions but with
concentrations that ranged from 31.25 to 1,000 μg/ml using
E. histolytica strainHM1:IMSS, and the IC50 values for each
extract were calculated. The chloroform extracts from Alpinia
galanga (IC50 55.2 μg/ml), Barleria lupulina (IC50
78.5 μg/ml), Boesenbergia pandurata (IC50 45.8 μg/ml),
Piper betle (IC50 91.1 μg/ml) and Piper chaba (IC50 71.4 μg/
ml) and the methanol extract from B. pandurata (IC50
57.6 μg/ml) were all classified as “active”, i.e. with an IC50
of less than 100 μg/ml, whereas those from Murraya
paniculata (IC50 116.5 μg/ml) and Zingiber zerumbet (IC50
196.9 μg/ml) were classified as being “moderately active”.
The IC50 of a standard drug, metronidazole, was 1.1 μg/ml.