Alkaloid classifications

Generally speaking, alkaloids are categorized under three main categories,depending on their biogenic origin. For those containing at least a nitrogen atom in a ring system derived from amino acids (i.e. alkaloids derived from phenylalanine are not grouped in this category), they are true alkaloids. The alkaloids derived from phenylalanine are categorized as protoalkaloids. While the remaining ones, such as steroidal alkaloids and purine alkaloids, are classified as pseudoalkaloids.

Alkaloids are usually classified by their common molecular precursors, based on the metabolic pathway used to construct the molecule.Fact: date=May 2009 When not much was known about the biosynthesis of alkaloids, they were grouped under the names of known compounds, even some non-nitrogenous ones (since those molecules' structures appear in the finished product; the opium alkaloids are sometimes called "phenanthrenes", for example), or by the plants or animals they were isolated from. When more is learned about a certain alkaloid, the grouping is changed to reflect the new knowledge, usually taking the name of a biologically-important amine that stands out in the synthesis process.Or: date=May 2009

• Pyridine group: piperine, coniine, trigonelline, arecoline, arecaidine, guvacine, cytisine, lobeline, nicotine, anabasine, sparteine, pelletierine.
• Pyrrolidine group: hygrine, cuscohygrine, nicotine
• Tropane group: atropine, cocaine, ecgonine, scopolamine, catuabine
• Indolizidine group: Senecionine
• Quinoline group: quinine, quinidine, dihydroquinine, dihydroquinidine, strychnine, brucine, veratrine, cevadine
• Isoquinoline group: opium alkaloids (papaverine, narcotine, narceine, morphine, codeine, heroine), sanguinarine, hydrastine, berberine, emetine, berbamine, oxyacanthine
• Phenanthrene alkaloids: opium alkaloids (morphine, codeine, thebaine)
• Phenethylamine group: mescaline, ephedrine, dopamine
• Indole group:
• Tryptamines: serotonin, DMT, 5-MeO-DMT, bufotenine, psilocybin
• Ergolines (the ergot alkaloids): ergine, ergotamine, lysergic acid
• Beta-carbolines: harmine, harmaline, tetrahydroharmine
• Yohimbans: reserpine, yohimbine
• Vinca alkaloids: vinblastine, vincristine
• Kratom (Mitragyna speciosa) alkaloids: mitragynine, 7-hydroxymitragynine
• Tabernanthe iboga alkaloids: ibogaine, voacangine, coronaridine
• Strychnos nux-vomica alkaloids: strychnine, brucine
• Purine group:
• Xanthines: caffeine, theobromine, theophylline
• Terpenoid group:
• Aconitum alkaloids: aconitine
• Steroid alkaloids (containing a steroid skeleton in a nitrogen containing structure):
• Solanum (e.g. potato and tomato) alkaloids (solanidine, solanine, chaconine)
• Veratrum alkaloids (veratramine, cyclopamine, cycloposine, jervine, muldamine)
• Fire Salamander alkaloids (samandarin)
• Others: conessine
• Quaternary ammonium compounds: muscarine, choline, neurine
• Miscellaneous: capsaicin, cynarin, phytolaccine, phytolaccotoxin