Complex sentence: Pyrrolizidine alkaloids (PAs), toxins the Bella Moth is able to ingest and use for protection from predators, are known to be the principal toxins found in plants that can cause disease in humans and other animals.
Split into simpler sentences: Pyrrolizidine alkaloids (PAs) are the toxins the Bella Moth is able to ingest and use for protection from predators. They are known to be the principal toxins found in plants that can cause disease in humans and other animals.