[3] Indonesian Gambier (U. gambir) is a large tropical vine with leaves typical of the genus, being opposite and about 10 cm (3.9 in) long.

Uncaria was named in 1789 by Johann von Schreber in his Genera Plantarum edition 8[a] (not to be confused with books of the same title by Linnaeus, Jussieu, and others).

[8] As of March 2023[update], Plants of the World Online accepted the following species:[9] Diplomat Edmund Roberts noted that, upon his visit to China in the 1830s, Chinese were using U. gambir for tanning, and noted that the U. gambir made "leather porous and rotten."

[10] The plant extract contains some 150 identified phytochemicals, including catechins, proanthocyanins, and chalcone-flavan-3-ol dimers, called gambiriins.

[11] Although cat's claw appears to be safe for human use below 350 milligrams per day over 6 weeks, its adverse effects may include nausea, diarrhea, upset stomach, and an increased risk of bleeding if used with an anticoagulant drug.