Based on the previously reported in vitro antiplasmodial activity of several xanthones from Garcinia mangostana , two xanthones, α‐mangostin and a new compound, δ‐mangostin, were isolated from mangosteen husk, and the in vitro antiplasmodial and cytotoxic effects were determined. α‐Mangostin was more active against the resistant Plasmodium falciparum chloroquine‐resistant (FCR3) strain (IC 50 = 0.2 ± 0.01 μM) than δ‐mangostin (IC 50 = 121.2 ± 1.0 μM). Furthermore, the therapeutic response according to the administration route was evaluated in a Plasmodium berghei malarial murine model. The greatest therapeutic response was obtained with intraperitoneal administration; these xanthones reduced parasitemia by approximately 80% with a daily dose of 100 mg/kg administered twice a day for 7 days of treatment. Neither compound was effective by oral administration. Noticeable toxicological effects were not observed. In addition to the antimalarial effect of these xanthones isolated from G. mangostana husk, the availability of larger amounts of husk raw material to purify the bioactive xanthones is advantageous, permitting additional preclinical assays or chemical transformations to enhance the biological activity of these substances. Copyright © 2015 John Wiley & Sons, Ltd.