Uncaria is a genus of approximately 40 species of woody lianas in the family Rubiaceae (order Gentianales), named by Johann von Schreber in 1789. The genus is best recognised by its distinctive climbing mechanism: reduced, modified branches form rigid hooks that allow the vines to scramble through and cling to surrounding vegetation. Leaves are opposite and typically around 10 cm long. Inflorescences are compact heads borne at the ends of very short horizontal branches, and the small seeds carry a long wing at each end, the lower wing deeply forked.
The genus has a pantropical distribution. The great majority of species are native to tropical Asia, from South and Southeast Asia through to southern China. Three species occur in Africa and the Mediterranean region, and two are native to the neotropics of South America. Colloquial names include gambier, cat's claw, and uña de gato, though these names are shared with several unrelated plants.
Uncaria is placed in the tribe Naucleeae within Rubiaceae, though its precise position within that tribe remains taxonomically unresolved. Notable members include Uncaria gambir (Indonesian gambier), a large tropical vine whose leaves and shoots yield a tannin-rich extract used historically in tanning and as a chewing adjunct with betel nut; and Uncaria tomentosa (South American cat's claw / uña de gato), widely used in traditional Amazonian medicine. Several Asian species, including Uncaria sinensis, are used in traditional Chinese medicine.
Etymology
The genus name Uncaria is derived from the Latin uncus, meaning "a hook." It was coined by Johann von Schreber in 1789 in his Genera Plantarum (edition 8) and refers to the distinctive hooks — reduced, modified branches — by which the vines grip surrounding vegetation.
Distribution
Uncaria has a pantropical distribution of roughly 40 species. The majority are native to tropical Asia, spanning South Asia, Southeast Asia, and southern China. Three species are found in Africa and the Mediterranean region, and two occur in the neotropics of South America. The type species, U. guianensis, is South American.
Taxonomy
Uncaria belongs to the tribe Naucleeae within the family Rubiaceae (order Gentianales). The genus was established by Johann von Schreber in 1789 (Gen. Pl. ed. 8[a]: 125). Its placement within Naucleeae is accepted but its precise relationships to other Naucleeae genera remain unresolved. The GBIF backbone recognises approximately 90 infraspecific and species-level taxa under the genus.
Cultural Uses
Uncaria gambir has been used for centuries in tropical Asia: the plant extract, rich in catechins, proanthocyanidins, and chalcone-flavan-3-ol dimers (gambiriins), was widely employed as a tanning agent and chewed with areca nut — a practice documented by diplomat Edmund Roberts in China in the 1830s. Uncaria tomentosa (South American cat's claw) and several Chinese Uncaria species are used in traditional medicine; as of current reviews, however, no high-quality clinical evidence supports medicinal efficacy for any species.
