Following statements are made regarding the plant natural product, alkaloids.

A. Alkaloids are nitrogen-containing compounds typically derived from amino acids.

B. Morphine is an alkaloid derived from the opium poppy.

C. Quinine, an anti-malarial compound, is an example of a purine alkaloid.

D. Caffeine is a xanthine alkaloid found in coffee.

Which one of the following options represents the combination of all correct statements?