Looking beyond simply “medicinal” properties, there are examples of plants that have evolved their chemical composition in response to animals. Hot peppers, for example. The capsaicin only affects mammals, not birds. Birds can eat the fruit and more widely disperse their seeds than mammals would. It’s advantageous to the plants that birds eat the fruit instead of mammals.

So it’s not unreasonable that other plants may have also developed specific chemicals in response to some pressure from animals.

Though in a twist it turns out that one specific mammal has spread hot peppers far more than any birds ever before.