Cleistanthus is a genus of flowering plants in the family Phyllanthaceae (order Malpighiales), placed in tribe Bridelieae. The genus was first formally described in 1848 and comprises a substantial number of species distributed widely across the Old World tropics, including Asia, Africa, Australia, and various oceanic islands.
Members of Cleistanthus are woody plants — predominantly trees and shrubs — characteristic of tropical and subtropical forests and scrublands across their range. The genus name and its placement within Phyllanthaceae links it to a largely tree-forming lineage within the eudicots, distinct from the more familiar spurge family (Euphorbiaceae) to which it was once allied.
The genus is perhaps best known outside botanical circles for Cleistanthus collinus, a species native to southern Asia that produces a potent plant toxin. Ingestion of its leaves or leaf decoctions causes severe hypokalemia, metabolic acidosis, and multi-organ failure, and the species has been implicated in poisoning cases across India and Sri Lanka. C. collinus is assessed as Vulnerable by the IUCN.
Taxonomy Notes
Cleistanthus is placed in the family Phyllanthaceae, order Malpighiales, within tribe Bridelieae. It was first described as a genus in 1848. Phyllanthaceae was historically treated as part of Euphorbiaceae but is now recognised as a distinct family in modern classifications.
Distribution
Cleistanthus is widespread across the Old World tropics, occurring in Asia, Africa, Australia, and various oceanic islands. Its range spans tropical and subtropical forest and scrubland habitats across these regions.
Cultural Uses
Cleistanthus collinus is known by multiple vernacular names across southern Asia — oduvan (Tamil), kadise (Kannada), Vadisaku (Telugu), Oduku (Malayalam), and Gaja Madara (Sinhala) — reflecting its longstanding local recognition. Its toxicity has made it a documented agent in poisoning cases in India and Sri Lanka.
