Well, now that we have Jesuits from the Americas in Corsica, I was thinking about possible agricultural transplants to Corsica, which brought up Jesuit's bark, which prompted a memory that someone had mentioned it in this TL before. After a search, I was pleasantly surprised it was me!
Well, the high-in-quinine bark of the cinchona tree (Jesuit's Bark) had been used a malarial curative for a while now. In fact, contemporaneous to this TL, the French naturalist Charles Marie de La Condamine was in Ecuador and published a paper on the taxonomy and medicinal properties of the varieties of cinchona trees in 1738. Our Theodore seems like the perfect philosopher king to make full utilization of such discoveries.