nitrogen metabolism alkaloid metabolism GO:0009820 UPa:UPA00414 Metabolism of alkaloids, a group of nitrogen containing natural products which are not otherwise classified as peptides, nonprotein amino-acids, amines, cyanogenic glycosides, glucosinolates, cofactors, phytohormones or primary metabolites (such as purine or pyrimidine bases). Alkaloids are usually found in plants. Various alkaloids have toxic or medical properties, such as caffeine, morphine and nicotine. pathway