medicines from plants found in dry climates?

Vinca alkaloids are a well-known family of medicinal compounds from vinca plants, which grow in dry climates. Cactus too has been found to have medical uses. I suspect dry climates force plants to develop defenses for their water supply. These defenses include the spines of the cactus, but also the chemicals they produce in their roots and shoots to keep animals, bacteria, fungi, and other plants away. 

I wonder about what medicinal compounds might be found in bristlecone pines, acacia, and baobab trees. 

All three are found in dry climates. Olive trees are also found in dry climates. The health benefits of olive oil were known in ancient times, but what about the trees themselves?

It seems that olive tree leaves are underused as a medicine.