Secondary metabolites
Unlike primary metabolism (growth), secondary compounds often defend against herbivores and pathogens but become pharmacologically active in humans at controlled doses.
Major classes
- Alkaloids — nitrogen-containing (morphine, caffeine, quinine)
- Terpenoids — built from isoprene units (menthol, artemisinin)
- Phenolics — flavonoids, tannins, coumarins
- Glycosides — sugar-bound active aglycones released by metabolism
Biosynthesis context
Production varies with plant age, organ, season, and stress. Harvest timing affects potency — often just before flowering for many herbs.