There is not a clear view of the extent of the toxicity of this plant. In 1964, a child is reported to have died after eating unripe roots. But it is said that the ripe fruits lose their toxicity.

The leaves are thought to have too rough a texture to encourage consumption of a large amount but there are reported cases of animal poisoning from eating the leaves and lab tests on rabbits have confirmed the toxicity.

I'm guessing that using the leaves to make tea would be a good way to extract the toxins and give yourself a really bad time.

Lantana tea??! Eeeyyuucchh!!! Almost certainly poisonous, too!