Alstonia macrophylla

Alstonia macrophylla, commonly known as large-leaved milkwood or devil tree, is a flowering tree in the family Apocynaceae. It holds an established place in the catalogue of ayurvedic medicinal plants of Sri Lanka, where its bark, leaves, and latex have been used in traditional healing systems for centuries. The tree grows naturally across tropical South and Southeast Asia, and in Sri Lanka it is found in lowland rainforests and disturbed secondary growth areas, particularly in the wet zone.

What does Alstonia macrophylla look like?

Alstonia macrophylla is a medium to large evergreen tree capable of reaching 20–30 metres in height under favourable conditions. Its most recognisable feature is its leaves, which are arranged in whorls of three to eight at each node and are notably large — hence the species epithet macrophylla, meaning "large leaf" in Latin. The leaves are leathery, dark green on the upper surface, and paler beneath.

The tree produces clusters of small, white to cream-coloured tubular flowers with a faintly sweet scent, typically blooming in the cooler months. The fruit consists of paired slender follicles that can reach considerable length and contain numerous seeds tipped with tufts of hair to aid wind dispersal. The bark is grey-brown, often fissured, and exudes a milky white latex when cut — a characteristic common across the Alstonia genus.

Where does Alstonia macrophylla grow in Sri Lanka?

In Sri Lanka, Alstonia macrophylla is most commonly found in the wet lowlands and intermediate zone forests. It tolerates disturbed habitats well and can often be found growing along roadsides, in home gardens, and on the edges of protected forest areas. The species also occurs within biodiversity-rich reserves such as the Sinharaja Forest Reserve, Sri Lanka's UNESCO-listed lowland rainforest in the Southern Province.

The tree prefers well-drained, moist soils and warm tropical temperatures. It is not typically found above mid-elevation zones, as it is adapted to humid, frost-free conditions.

What are the traditional ayurvedic uses of Alstonia macrophylla?

In Sri Lankan and broader South Asian ayurvedic traditions, various parts of Alstonia macrophylla have been used medicinally. The bark is the most commonly referenced part and has historically been employed as a febrifuge — that is, a treatment to reduce fever. It has also been used in formulations addressing malarial-type fevers, digestive complaints, and as a general bitter tonic.

The latex and bark contain a range of alkaloids that are of ongoing scientific interest for their pharmacological properties. Traditional practitioners have applied bark preparations externally in the management of skin conditions and ulcers, while internally it has been used in small, carefully measured doses as part of compound herbal remedies.

• Bark: Febrifuge, bitter tonic, treatment for digestive disorders
• Latex: Applied externally for skin complaints and wound care in traditional practice
• Leaves: Used in some regional traditions as part of poultices

It is important to note that like many potent medicinal plants, Alstonia macrophylla should only be used under the guidance of a qualified ayurvedic physician. The alkaloids present in the bark can be toxic if consumed inappropriately.

How does Alstonia macrophylla relate to other Sri Lankan medicinal plants?

Sri Lanka's ayurvedic pharmacopoeia is one of the richest in Asia, drawing on an island ecosystem that supports an exceptional diversity of plant species. Alstonia macrophylla sits alongside a broad range of botanicals that have been integrated into the island's indigenous medical system, Deshiya Chikitsa, for over two thousand years.

Other trees with comparable roles in Sri Lankan traditional medicine include Pongamia pinnata, which is valued both for its medicinal properties and its oil-yielding seeds, and Acacia chundra, whose heartwood has long been used in ayurvedic formulations. Together, these species form part of a living pharmacopoeia that continues to inform both traditional and modern herbal medicine research in Sri Lanka.

Is Alstonia macrophylla used in modern research?

Scientific interest in Alstonia macrophylla has grown considerably over recent decades. Researchers have isolated and studied a variety of indole alkaloids from the bark and leaves, several of which have demonstrated activity in laboratory settings relevant to antimalarial, anti-inflammatory, and antimicrobial research. These findings broadly validate the plant's long-standing traditional uses, though clinical trials in humans remain limited.

Sri Lanka's Department of Ayurveda and several university faculties of medicine maintain ongoing programmes documenting and studying the country's medicinal plant heritage, with species like Alstonia macrophylla forming part of that formal record. The plant is listed in official Sri Lankan ayurvedic catalogues, which serve as reference documents for practitioners and researchers alike.

Can visitors learn about Sri Lanka's medicinal plants?

For travellers curious about Sri Lanka's botanical traditions, there are several meaningful ways to engage with the island's herbal heritage. Spice and herb gardens — particularly those in the Kandy and Matale regions — offer guided tours explaining the traditional and contemporary uses of plants including those from the Apocynaceae family. Ayurvedic wellness retreats across the island also provide introductions to the plant-based ingredients used in treatments.

Those interested in the intersection of Sri Lanka's ecology and its plant life may also find value in exploring protected forest areas where species like Alstonia macrophylla grow in their natural habitat. Sri Lanka's wet zone forests, from the lowland reserves of the south to the cloud forests of the central highlands, represent some of the most botanically diverse environments in Asia.