This document discusses two methods of classifying alkaloids: biosynthetic classification and chemical classification. Biosynthetic classification is based on the precursor compounds that alkaloids are derived from during plant biosynthesis, such as tryptophan, lysine, ornithine, and tyrosine. Chemical classification is based on the presence of the basic heterocyclic nucleus and lists examples of alkaloid classes including piperidine, pyrrolidine, quinoline, isoquinoline, indole, and steroidal alkaloids.

9. (a) Biosynthetic Classification - alkaloids are produced in
the plant biosynthetically. all alkaloids having been derived
from the same precursor but possessing different taxonomic
distribution and pharmacological activities.
Examples
(i) Indole alkaloids derived from tryptophan.
(ii) Piperidine alkaloids derived from lysine.
(iii) Pyrrolidine alkaloids derived from ornithine.
(iv) Phenylethylamine alkaloids derived from tyrosine.
(v) Imidazole alkaloids derived from histidine.

10. (b) Chemical Classification- is the presence of the basic heterocyclic
nucleus
Examples
(i) Pyrrolidine alkaloids e.g., Hygrine;
(ii) Piperidine alkaloids e.g., Lobeline;
(iii) Pyrrolizidine alkaloids e.g., Senecionine;
(iv) Tropane alkaloids e.g., Atropine;
(v) Quinoline alkaloids e.g., Quinine;
(vi) Isoquinoline alkaloids e.g., Morphine;
(vii) Aporphine alkaloids e.g., Boldine;
(viii) Indole alkaloids e.g., Ergometrine;
(ix) Imidazole alkaloids e.g., Pilocarpine;
(x) Diazocin alkaloids e.g., Lupanine;
(xi) Purine alkaloids e.g., Caffeine;
(xii) Steroidal alkaloids e.g., Solanidine;
(xiii) Amino alkaloids e.g., Ephedrine;
(xiv) Diterpene alkaloids e.g., Aconitine.