Concept:
Quinine is a natural antimalarial alkaloid.
Step 1: Quinine is obtained from Cinchona bark.
Step 2: Cinchona bark contains quinoline alkaloids.
Step 3: Quinine was historically one of the most important antimalarial drugs.
Step 4: Artemisia annua gives artemisinin, not quinine.
\[
\boxed{\text{Cinchona bark}}
\]