because DHA is the common active metabolite of all derivatives.

Thanks. But are results different depending on which of the two used for the assay?

Hi Devendra,

Dihydro-artemisinin (DHA) is an artemisinin (ART) derivative. ART derivatives are frontline drugs used in ART-based combination therapies (ACTs) and they are metabolized to DHA rapidly which is about seven times more potent than the parent compound in vitro. Ring stage parasites can remain dormant and recover rapidly later leading to numerous parasites enduring DHA-exposed dormancy. Thus, in P. falciparum strains in vitro IC50 values calculated by traditional 48 h exposure assay were low while it is not known whether this is the case in vivo as well. Thus, trying to develop more accurate in vitro assays for to monitor ART resistance, ring-stage survival assay (RSA) was recently developed. In RSA, sorbitol synchronized ring-stage parasite cultures are exposed to 700 nmol/L DHA and 0.1 % DMSO controls for 6 h, washed 2,3 times and then cultivated for 66 h. Finally, survival rates are calculated as the ratio of viable parasites surviving DHA-induced incubation relative to initial conditions. Kelch domain gene (K13) mutation is believed to be implicated in ART resistance, has shown to have correlation with RSA.

Hope this helps!!