Alchornea is a genus of approximately 50 species of trees and shrubs in the spurge family Euphorbiaceae, placed in the order Malpighiales. First described by Olof Swartz in 1788, the genus is widespread across tropical and subtropical regions of Africa, South Asia, East Asia, Australia, Latin America, and various oceanic islands.
Plants in the genus are typically dioecious or monoecious trees and shrubs with simple, alternate leaves. The leaf blade is notably glandular at the junction with the petiole (usually bearing 2–4 glands) and commonly has a pair of stipels at the base. Leaves may be pinnately veined with short petioles, or palmately veined with long petioles, and the margins are crenate to dentate. Inflorescences are terminal or axillary; male flowers are clustered (fascicled), lack petals, and carry 4–8 stamens; female flowers bear 2–3 elongated, free styles. The fruit is a smooth or muricate capsule with 2–4 locules, and seeds are globose and often tuberculate.
The genus is particularly species-rich in Africa and tropical Asia. Eight species occur in China (three endemic), and several species inhabit Neotropical floodplain forests, where they can tolerate prolonged seasonal inundation. Molecular phylogenetic work has shown that Bocquillonia, a small New Caledonian genus, is nested within Alchornea, a finding that may eventually lead to the synonymisation of that genus.
Several species have ethnobotanical significance. Alchornea castaneifolia, known as Iporuru in the Peruvian Amazon, is a well-known medicinal tree whose bark and leaves contain alkaloids (including alchorneine) with anti-inflammatory and analgesic properties, long used by indigenous Amazonian peoples for arthritis, rheumatism, and related ailments. Alchornea cordifolia, the Christmas bush of West Africa, is widely used in African traditional medicine.
Etymology
The genus name Alchornea honours Stanesby Alchorne (1727–1800), an English apothecary and botanist who served as assay master of the Royal Mint. The genus was established by Olof Swartz in his Prodromus of 1788.
Distribution
Alchornea is distributed throughout tropical and subtropical regions worldwide, with a particular concentration of species in Africa and tropical Asia. About 50 species are recognised; 8 occur in China (3 endemic to China), and multiple species inhabit Neotropical and Afrotropical forests. The genus extends to South Asia, Australia, and various oceanic islands.
Ecology
Several Alchornea species are adapted to seasonally flooded habitats. Alchornea castaneifolia of Amazonian South America grows in floodplain forests and can remain submerged for the duration of the wet season, with local collectors harvesting its bark only during the dry season. Species across the genus occur in moist to wet forest environments, from lowland tropical rainforest to subtropical woodland.
Cultural Uses
Alchornea castaneifolia (Iporuru) is a significant medicinal plant of the Peruvian and Amazonian tradition. Its bark and leaves are prepared as decoctions and tinctures to treat rheumatism, arthritis, osteoarthritis, colds, and muscle pain. The anti-inflammatory action is attributed to a group of alkaloids, notably alchorneine, found in the bark. The plant is also used as an aphrodisiac, geriatric tonic, and occasional ingredient in ayahuasca preparations by indigenous groups including the Candochi-Shapra and Shipibo. Alchornea cordifolia, the Christmas bush of West Africa, has an extensive parallel history in African ethnomedicine.
