Cat's Claw
Uncaria tomentosa
Cat's Claw (Uncaria tomentosa) is a large woody vine of the Amazon rainforest, named for the distinctive curved, claw-like thorns that grow from its leaf axils and help it climb high into the forest canopy. This powerful medicinal plant, revered for centuries by indigenous peoples of the Amazon basin, has become one of the most important and widely researched botanical medicines in the world. Its bark and roots contain a complex mixture of oxindole alkaloids that have demonstrated potent anti-inflammatory, immunostimulant, and antioxidant properties in scientific studies.
• One of the most important medicinal plants of the Amazon rainforest
• Named for the curved, claw-like thorns that resemble a cat's claws
• Contains over 30 known alkaloids with documented pharmacological activity
• Has been used by Ashaninka, Campa, and other Amazonian peoples for over 2,000 years
• The genus Uncaria contains about 40 species distributed across the tropics
Taxonomy
• Found in Peru, Bolivia, Colombia, Ecuador, Guyana, Suriname, Venezuela, and Brazil
• Grows in primary and secondary tropical rainforests from sea level to approximately 800 m
• Prefers moist, humid forest environments along river margins and in lowland tropical forest
• Most abundant in the central Amazon basin of Peru and Brazil
• First described by the Spanish botanists Hipólito Ruiz López and José Antonio Pavón Jiménez from specimens collected in Peru
• The species epithet "tomentosa" refers to the dense, woolly (tomentose) hairs covering young parts of the plant
• Indigenous Ashaninka people of Peru have used Cat's Claw medicinally for millennia, treating asthma, arthritis, inflammation, and gastrointestinal disorders
• Introduced to modern Western herbal medicine in the 1970s through the work of Austrian ethnobotanist Klaus Keplinger
• Now commercially harvested from wild populations, raising sustainability concerns
Stem:
• A woody vine (liana) climbing 15-30 m into the rainforest canopy
• Main stem is woody, cylindrical, 2-8 cm in diameter in mature specimens
• Bark: yellowish-brown to dark brown, rough, with longitudinal fissures
• The inner bark is the primary part used medicinally, fibrous and slightly bitter
Thorns:
• The most distinctive feature: recurved, woody thorns 1-3 cm long growing from the leaf axils
• Thorns are stout, sharply curved like a cat's claw, functioning as climbing hooks
• Thorns grip host tree bark, allowing the vine to ascend into the canopy
Leaves:
• Simple, opposite, elliptic to ovate-lanceolate, 8-18 cm long and 4-8 cm wide
• Dark glossy green above, paler and pubescent (hairy) beneath, particularly along the veins
• Young leaves and stems are covered in fine, whitish tomentose hairs
• Petioles 1-3 cm long; stipules interpetiolar, ovate, persistent
Flowers:
• Small, tubular, yellowish-white to greenish-white, 1-1.5 cm long
• Arranged in dense, globose heads (capitula) 2-3 cm in diameter
• Inflorescences are borne on specialized flowering shoots with reduced leaves and thorns
• Fragrant, attracting diverse insect pollinators
Fruit:
• Small, elongated capsules 8-15 mm long
• Splitting open to release numerous tiny, winged seeds
• Wind-dispersed
• A canopy-climbing liana that creates structural connections between trees
• Flowers provide nectar for diverse insect communities, particularly bees and butterflies
• Dense vine tangles in the canopy provide nesting and roosting habitat for birds and arboreal mammals
• Seeds are wind-dispersed from the elevated canopy position
• Thorny stems deter large herbivores from browsing
• Bark alkaloids (oxindole alkaloids, quinovic acid glycosides) serve as chemical defenses
• Plays a role in forest dynamics by creating canopy connections and increasing structural complexity
• Wild harvesting for the medicinal trade has reduced populations in accessible areas
• Sustainable harvesting practices involve stripping only portions of bark rather than felling the vine
• Requires hot, humid tropical conditions with annual rainfall exceeding 2,000 mm
• Prefers well-drained, fertile, loamy forest soils rich in organic matter
• Propagation is by seed or stem cuttings
• Seeds should be collected from mature capsules and sown fresh
• Germination can be slow and irregular (30-90 days)
• Stem cuttings root best in warm, humid, shaded conditions
• Requires a support structure (tree or trellis) for the climbing growth habit
• Grows best under partial shade, mimicking forest understory conditions
• Takes 5-8 years to produce harvestable bark from cultivated plants
• Sustainable bark harvesting involves removing vertical strips while leaving the vine alive
• Can be integrated into agroforestry systems with shade-providing overstory trees
• Most commercial supply still comes from wild harvesting in the Amazon
Fun Fact
Cat's Claw became an international herbal medicine sensation in the 1990s when studies showed its oxindole alkaloids could stimulate the immune system. Today it is one of the top-selling herbal supplements in the United States and Europe. Ironically, the vine's rise to fame has put wild populations at risk — an estimated 10,000-20,000 kg of Cat's Claw bark is harvested from the Peruvian Amazon each year, much of it destructively by cutting entire vines rather than sustainably stripping bark.
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