Objective: To understand the druggability of dichroa alkali salt (DAS) as an antimalarial drug by investigating its antimalarial efficacy and toxicity characteristics. Method: The animal models of malaria were established by inoculating strains of the parasite in an antimalarial experiment in vivo. The model mice received drugs by intragastric administration

once daily

for 4 d. Blood from the caudal vein was dynamically collected for blood smear. Giemsa staining assay was used to observe the negative conversion and revival of parasite under a microscope in each group. Finally

negative conversion ratio

anti-revival ratio

and 50% effective dose (ED50) were calculated. ICR mice were used to study the acute toxicity of DAS

observe their general state

diarrhea and death. 50% diarrhea dose (DD50) and 50% lethal dose (LD50) were calculated

while hematoxylin-eosin (HE) staining was used to observe the histopathological changes of the main organs. Result: The antimalarial experimental results showed that DAS was effective in antimalarial treatment at a lower dose

with an ED50 of 0.6 mg·kg-1 and a 95% confidence interval of 0.5 to 0.7 mg·kg-1

but no obvious effect was observed in anti-revival. The acute toxicity experiment of mice showed that after DAS was given

the mice activities were decreased

the behavior was sluggish

and the hair color was dull; the mice were in fear of cold

with poor food and water intake. Diarrhea was found in the mice with mild toxic degree

and hematochezia and death were even found in those with severe toxic degree; DD50 was 7.9 mg·kg-1

with 95% confidence interval of 6.3-10.0 mg·kg-1; LD50 was 10.8 mg·kg-1

with 95% confidence interval of 8.5-13.8 mg·kg-1. The general anatomy results showed that the stomach of mice in treatment group was obviously extended

with atrophy in spleen and cecum

and swill like changes in intestinal contents. HE staining showed that the liver

spleen

stomach and cecum had different degrees of histopathological injury. With DD50 and LD50 as the indicators

the therapeutic index (TI) of DAS was calculated as 13.17 and 18.00 respectively. Conclusion: DAS is effective but toxic for malaria at an even lower dose

with narrow safe dose window.