Artesunate-d is intended for use as an internal standard for the quantification of artesunate by GC- or LC-MS. Artesunate is a derivative of artemisinin that is active against P. falciparum in vitro (IC = 1.28 nM). It is an iron(II) oxide-reactive endoperoxide that generates reactive oxygen species (ROS) upon cleavage of its endoperoxide bridge. It inhibits the activity of the P. falciparum EXP1, a glutathione S-transferase (GST) that degrades hematin, with an IC value of 2.05 nM. Artesunate inhibits proliferation of germinal center B cells in vitro and prevents development of arthritis via inhibition of germinal center formation and autoantibody production in the K/BxN mouse model of rheumatoid arthritis when administered at a dose of 100 mg/kg twice per day. It also inhibits alveolitis and pulmonary fibrosis induced by bleomycin in rats. Artesunate increases the activity of GST in mice infected with P. berghei compared to uninfected and infected control animals.