Uncaria is a genus of flowering plants in the family Rubiaceae. 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. The South American U. tomentosa is called Uña de Gato. Uncaria sinensis is common in China. Uncaria sinensis (Oliv.) Havil., Lianas, height unknown. Young stems slender, quadrangular, glabrous. Petiole 6-10 mm, glabrous; leaf blade drying thinly papery, elliptic to ovate, 9-14 × 5-8.5 cm. Six constituents have been isolated from the hooks and stems of Uncariasinensis. Five new 16-carboxy derivatives of oxindole alkaloids isopteropodic acid, pteropodic acid, mitraphyllic acid, isorhynchophyllic acid and rhynchophyllic acid, have been identified along with one known coumarin, scopoletin.