The genus was given the name Mitragyna by Korthals because the shape of the stigmas in the species he examined resembled a bishop's mitre. However the nomenclature has frequently been confused, the genus being variously named as Nauclea, Sarcocephalus, Stephegyne and Uncaria though consistently recognised as members of the tube Naucleeae in the sub-family Naucleoideae. There has also been some confusion at species level but today the species are recognized as follows:

West Africa:

Mitragyna inermis (Willd.) O. Kuntze ( M. africana (Willd.) O. Kuntze)
Mitragyna ciliata Aubrev. and Pellegr. ( M. macrophylla Hiern)
Mitragyna stipulosa (D.C.) O. Kuntze ( M. macrophylla Hiern)

East Africa:

Mitragyna rubrostipulata Havil.

India and S.E. Asia:

Mitragyna hirtusa Havil.
Mitragyna javanica Koord. and Valeton.
Mitragyna parvifolia (Roxb.) Korth.
Mitragyna rotundifolia (Roxb.) O. Kuntze (N. diversifolia (Hook.f.) Havil.)
Mitragyna speciosa Korth.
Mitragyna tubulosa Havil.
Mitragyna brunnonsis (Wall ex G.Don) has been included in M. rotundifolia.

In a more recent revision of the genus (1972) R.C. Bakhuisen van den Brink (Leiden Herbarium) has included Mitragyna javanica in M. parvifolia though whether this can be justified on chemotaxonomic grounds remains to be argued.

To date (1974e.v.) 40 alkaloids have been isolated and characterized. These are given in tables 2-5 (pp. 47-48 ).