i was bio in college. you be fascinated how certain plants produce thier toxin, and how they make it biochemically. obviously for plants they dont want be eaten so they produce very toxic compounds. and then things like certain insects evolved to deal with toxins. just think of native milkweeds and monarch butterflies , they evolved to concentrate the milkweed poisons it in thier bodies. simarly certain swallowtail related to monarchs use plants called aristholcia(ornamental plants too) the plants are quite toxic, and carcinogenic.