I am sorry I am not sure what you asking me. Which terms are used interchangeably ? Are you asking about Phytochemistry and Pharmacology ? Phytochemistry is the study of the chemistry of plants, Pharmacology is totally different it is the uses, effects and modes of actions of plants, drugs or phytochemicals. So this statement : includes flavonoids, minerals, vitamins, is totally incorrect, Pharmacology is the effects of the plant or individual substances, not the groups of chemicals.