Puberulic acid, a tropolone compound, has antibacterial and 
antimalarial activities. In this study, we investigated the in vitro
inhibitory effects of puberulic acid on three Babesia species and 
Theileria equi. Puberulic acid inhibited the growth of Babesia bovis, 
Babesia bigemina, Babesia caballi, and Theileria equi with IC50 values 
of 1.79 ± 0.3, 1.58 ± 0.2, 2.6 ± 0.3, and 3.83 ± 0.4 µM, respectively, 
starting from an initial parasitemia of 1%. At 5 M, puberulic acid 
completely inhibited growth in B. caballi, 10 µM in B. bovis, and 25 µM 
in B. bigemina and T. equi cultures. Parasite growth was inhibited in 
the viability test at concentrations of 5 µM for B. bigemina and B. 
caballi, 10 µM for B. bovis, and 100 µM for T. equi. Puberulic acid had 
higher IC50 values than diminazene aceturate. At the concentrations 
used, the DMSO solvent did not influence the growth of the parasites.
According to the in vitro results, puberulic acid may be a promising 
candidate for developing a new antibabesial drug. More research, 
including extensive in vivo assessment, is urgently needed.