Licarin-B Exhibits Activity Against the RH Strain by Damaging Mitochondria and Activating Autophagy.

is an obligate intracellular pathogen that infects warm-blooded animals and humans. However, side effects limit toxoplasmosis treatment, and new drugs with high efficiency and low toxicity need to be developed. Natural products found in plants have become a useful source of drugs for toxoplasmosis. In this study, twenty natural compounds were screened for anti- activity by Giemsa staining or real-time fluorescence quantitative polymerase chain reaction (qPCR) . Among these, licarin-B from nutmeg exhibited excellent anti- activity, inhibiting invasion and proliferation in a dose-dependent manner, with an EC of 14.05 ± 3.96 μg/mL. In the , licarin-B treatment significantly reduced the parasite burden in tissues compared to no treatment, protected the 90% infected mice from to death at 50 mg/kg.bw. Flow cytometry analysis suggested a significant reduction in survival after licarin-B treatment. Ultrastructural changes in were observed by transmission electron microscopy (TEM), as licarin-B induced mitochondrial swelling and formation of cytoplasmic vacuoles, an autophagosome-like double-membrane structure and extensive clefts around the nucleus. Furthermore, MitoTracker Red CMXRos, MDC, and DAPI staining showed that licarin-B promoted mitochondrial damage, autophagosome formation, and nuclear disintegration, which were consistent with the TEM observations. Together, these findings indicate that licarin-B is a promising anti- agent that potentially functions by damaging mitochondria and activating autophagy, leading to death.