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Blackboard Tree (Alstonia scholaris): A Comprehensive Reference

1. Identity and Botanical Classification

Nomenclature and Taxonomy

Alstonia scholaris (L.) R.Br., commonly called the blackboard tree, scholar tree, milkwood, or devil's tree, is an evergreen tree in the oleander and frangipani family Apocynaceae. Linnaeus named the plant Echites scholaris in 1767, and in 1811, Robert Brown renamed the genus Alstonia in memory of Prof. Charles Alston. Synonyms of the plant include Echites scholaris L., Echites pala Ham., and Tabernaemontana alternifolia Burm.

The species epithet scholaris was derived from the use of its wood in making blackboards for schools in Southeast Asia. The genus Alstonia comprises about 60 species throughout the world, and about 6 species occur in India.

Common Names and Regional Synonyms

The tree is known by a wide range of regional names, including: chhatim and chitan (Bangladesh and India); saptaparni (India); popeal khe (Cambodia); tang jiao shu (China); pulai (Indonesia); dtin pet (Laos); basong, pulai, and rejang (Malaysia); let ban kha, lettok, taungmek (Myanmar); ditaa (Philippines); and suȧ, mo cua (Vietnam). In India, it is locally recognized as Saptaparna in Sanskrit, Chatian in Hindi, and Satvin in Marathi.

Physical Description and Natural Range

Alstonia scholaris is a large tree growing up to 40 m (130 ft) tall, rarely to 60 m, with narrow buttresses that extend well up the trunk, giving it a fluted appearance. The bark is gray to pale gray with numerous lenticels, and all parts of the plant exude copious amounts of white sap when broken or cut. The leaves are glossy dark green above and pale below, arranged in whorls of four to eight, with petioles around 5–15 mm long. The tree produces fragrant, star-shaped flowers that are white to cream in color, arranged in large clusters known as racemes, blooming mainly between late summer and early fall.

Its natural range extends from Pakistan to China, and south to northern Australia. It has wide occurrence also in the Asia-Pacific region — from India and Sri Lanka through mainland Southeast Asia and Southern China, throughout Malaysia to northern Australia and the Solomon Islands.

Plant Parts Used and Common Preparations

The medically significant parts of the plant include the stem bark, leaves, roots, and milky latex. Traditional preparations have included fresh bark extract in milk for leprosy and dyspepsia, and formulas such as Amritashtakapachana — valued for debility, after-effects of fever, chronic diarrhoea, dysentery, and catarrhal fever — as well as decoctions for the after-effects of malaria. At present, the leaf crude water extract is prepared as a tablet or granule and sold as therapeutic drugs for the treatment of tracheitis and the common cold, primarily in China. Bark decoctions, powders, poultices, and hydroalcoholic extracts are all reported in the ethnobotanical and pharmacological literature.

2. Traditional and Historical Use

Ayurvedic Tradition (Indian Subcontinent)

Alstonia scholaris has a long history of use in traditional and homeopathic medicine, including Ayurvedic medicine in India, where it is known as sapthaparna. The historical significance of Alstonia scholaris is well documented in ancient Ayurvedic texts, where it is referred to by various names including Saptaparna and Vishalatwak; classical texts such as the Charaka Samhita and Sushruta Samhita provide pharmacological insights about the plant and elaborate on its uses in treating ailments. It is mentioned in the Charaka Samhita under the Krimighna (anti-parasitic) and Kusthaghna (anti-skin disease) groups.

Historically, in tribal medicine — particularly among Adivasi communities in central and eastern India — the bark was given as a decoction for treating chronic diarrhoea, dysentery, and even malaria. British botanists like William Roxburgh documented the tree extensively in the 18th century, fascinated by its medicinal latex and how local vaidyas used it to treat fevers and worms. Over time, usage spread from traditional Ayurvedic physicians to Siddha and Unani practitioners.

In Ayurveda, the tree is used in treatments for malaria, fever, and dysentery, and is a key ingredient in the herbal formulation Ayush-64. Literature suggests that Alstonia scholaris is useful in treating malaria, abdominal disorders, dyspepsia, leprosy, skin diseases, tumors, chronic and foul ulcers, asthma, bronchitis, helminthiasis, agalactia, and debility.

Traditional Chinese Medicine and Dai Ethnopharmacy

In the Dai Ethnic regions of Yunnan Province, China, A. scholaris leaves are considered a therapy for respiratory diseases including whooping cough, chronic bronchitis, chronic obstructive pulmonary disease, and asthma. The leaf crude extract, used for relieving tracheitis and cold symptoms, was approved as a commercial formulation by the State Food and Drugs Administration of China (SFDA).

Southeast Asian and Other Traditions

Alstonia scholaris is extensively used in traditional medicinal systems of India, Thailand, Malaysia, Philippines, China, Africa, Australia, and elsewhere; in Thailand, it was commonly employed as a general tonic, aphrodisiac, anticholeric, antidysenteric, antipyretic, emmenagogue, and vulnerary agent. In folklore medicine, the milky juice of the plant is applied on injuries and ulcers to treat pain, including rheumatic pains.

Cultural and Symbolic Significance

The tree is called Saptaparna in India and is the sacred tree of the second Jain Tirthankar Ajitnatha. At Visva-Bharati University in Santiniketan, founded by Rabindranath Tagore, leaves of Alstonia scholaris are awarded to graduating students during annual convocation ceremonies — a practice initiated by Tagore to symbolize knowledge and growth — drawing from the tree's vernacular association with scholarship and the historical use of its wood for crafting blackboards.

3. Key Constituents and Active Compounds

Alkaloid Profile

The dominant and pharmacologically most studied class of compounds in Alstonia scholaris is monoterpenoid indole alkaloids. The plant is reported to contain a large number of alkaloids including echitamine, 17-O-acetyl echitamine, echitamine chloride, nareline, rhazine, vallesamine, scholaricine, scholarine, picrinine, N1-methoxymethyl picrinine, tubotaiwine, lagumamine, pseudo akuammigine, angustilobine B acid, losbanine, 6,7-secoangustilobine B, manilamine, N4-methyl angustilobine B, dihydrocondylocarpine, alschomine and isoalschomine, mataranine A and B, picralinal, corialstonidine and corialstonine.

The stem bark has been reported to contain alkaloids such as alstonidine, alstonine, alstovenine, chlorogenic acid, ditamine, echitamine, echitein, porphyrine, reserpine, venenatine, villalstonine, pleiocarpamine, O-methylmacralstonine, macralstonine, macrocarpamine, corialstonine and corialstonidine, as well as triterpenoids including lupeol linoleate, lupeol palmitate, and alpha-amyrin linoleate.

Leaf Constituents

The leaves contain quercetin, ursolic acid, alstonamine, alschomine, scholaricine, isorhamnetin, isorhamnetin-3-O-β-D-galactopyranoside, streptomycerol, β-sitosterol, akuammidine, angustilobine-B acid, losbanine, rhazimanine, and lagunamine.

Other Phytochemical Classes

Most of the pharmacotherapeutic effects of A. scholaris have been attributed to the presence of various phytoconstituents such as alkaloids, coumarins, iridoids, flavonoids, leucoanthocyanines, steroids, tannins, phenolics, and saponins. Identified flavonoids include isookanin-7-O-alpha-L-rhamnopyranoside, alstonoside, and leucoanthocyanins.

Mechanisms of Action

The alkaloids fraction from the leaf of A. scholaris ameliorated oedema, inflammation, and pain through inhibiting the inflammatory mediators COX-1, COX-2, and 5-LOX; three indole alkaloids — picrinine, vallesamine, and scholaricine — were identified as the principal active components. These three compounds were further identified as potential NF-κB inhibitors using a dual-luciferase reporter assay, and as β₂-adrenergic receptor (β₂AR) agonists through a relaxant test on guinea pig tracheal muscles.

Alkaloids increased significantly SOD activity and decreased levels of NO, PGE₂, and MDA in an air-pouch mouse model. Experimental studies have revealed anti-cancerous, anti-hypertensive, anti-inflammatory, analgesic, antidiabetic, nephroprotective, and neuroprotective activities attributed to phytochemicals such as alstonine, echitamine, picrinine, vallesamine, and scholaricine; extracts from A. scholaris containing high flavonoid and phenolic components are used to prevent oxidative stress-mediated hepatic, cardiac, neuronal, and renal injuries.

Echitamine in particular possesses a broad battery of pharmacological and autonomic activities, including anticancer activities. Corialstonine and corialstonidine, alkaloids of Alstonia scholaris, are active against Plasmodium falciparum.

Methanolic extracts of Alstonia scholaris flower and fruit showed significant antioxidant activity by inhibiting DPPH and superoxide production. Free radical scavenging activity has been attributed in part to the presence of flavonoids.

4. Scientific Evidence by Area of Use

4.1 Respiratory Conditions (Antitussive, Antiasthmatic, Expectorant)

This is currently the area with the most developed evidence base, driven largely by Chinese research programs.

Preclinical evidence: A. scholaris extracts and alkaloids have shown antitussive, anti-asthmatic, and expectorant effects, as well as analgesic, anti-inflammatory effects and airway anti-inflammation in vivo. Indole alkaloids including picrinine, scholaricine, vallesamine, and 19-epischolaricine are known to be responsible for antitussive, anti-asthmatic, expectorant, analgesic, anti-inflammatory, anti-airway-inflammation, anti-allergic-asthma, anti-post-infectious-cough, and effects alleviating emphysema and pulmonary fibrosis.

Regulatory status in China: The defined indole alkaloids from the leaf of A. scholaris have been registered as an investigational new botanical drug (No. 2011L01436) and were approved for Phase I/II clinical trials by the China Food and Drug Administration (CFDA).

Phase I human clinical trial (safety and tolerability): A capsule of alkaloids from the leaf of Alstonia scholaris (CALAS) was developed as a new investigational botanical drug for bronchitis, post-infectious cough, and asthma. Subjects were assigned to eight cohorts, each receiving CALAS or placebo in single ascending doses (SAD) of 8, 40, 120, 240, 360, or 480 mg, or multiple ascending doses (MAD) of 40 or 120 mg three times daily for 7 days. Sixty-two enrolled volunteers completed the study; no serious adverse events and no clinically significant changes in vital signs, electrocardiography, or abdominal Doppler ultrasonography were observed. Treatment-emergent adverse events (TEAEs) were reported in 23.91% of the CALAS groups and 18.75% of the placebo group (p > 0.05); all TEAEs were mild, transient, and disappeared without intervention. TEAEs possibly related to CALAS included hiccups (8%), dry mouth and nausea (6%), increased sleep (4%), abdominal distension (2%), and elevated bilirubin (2%). The investigators concluded that CALAS is safe and well-tolerated with no unexpected or clinically relevant safety concerns up to a single dose of 360 mg and three times daily for 7 days up to 120 mg in healthy Chinese volunteers, supporting further Phase II studies.

Pharmacokinetics in acute bronchitis patients: Alstonia scholaris is widely distributed in Southern China and is typically used for the treatment of acute and chronic respiratory diseases. A further clinical pharmacokinetics study of CALAS in acute bronchitis patients has also been conducted. Overall, the evidence in the respiratory area is the strongest currently available for A. scholaris as a dietary supplement, progressing from animal models through Phase I human trials, though Phase III efficacy trials in clinical respiratory disease populations have not yet been reported in the accessible literature.

4.2 Antimalarial Activity

Both Alstonia scholaris and Alstonia macrophylla have a long reputation in traditional medicine for the treatment of malaria. Early clinical trials conducted in Manila hospitals and in India demonstrated the ability of this plant to decrease malarial fever. In Ayurvedic medicine, this plant holds great esteem as an antimalarial agent. Corialstonine and corialstonidine, alkaloids of A. scholaris, have been documented as active against Plasmodium falciparum. Nevertheless, antimalarial activity has been little explored in correlation with specific alkaloid constituents, which is essential to validate the traditional claim against malaria. The evidence remains primarily historical and in vitro/animal-level; modern controlled clinical trials specifically for malaria are lacking.

4.3 Anti-inflammatory and Analgesic Activity

The ethanolic extract, EtOAc and alkaloid fractions of A. scholaris leaves remarkably inhibited xylene-induced ear edema in mice; further investigation on the alkaloids fraction showed it reduced acetic acid-induced writhing response and xylene-induced ear edema in mice. In the hot-plate test, alkaloids did not increase the latency period of mice; in the formalin test, alkaloids did not inhibit licking time in the first phase but significantly inhibited licking time in the second phase. The three main alkaloids picrinine, vallesamine, and scholaricine appear to produce anti-inflammatory and analgesic effects peripherally, based on several in vivo assays. This evidence is entirely preclinical (animal models); no human controlled trials on pain or inflammation as primary endpoints have been published.

4.4 Anticancer Activity

Echitamine chloride from Alstonia scholaris has demonstrated anticancer activity. Echitamine chloride, an indole alkaloid extracted from the bark of A. scholaris, has shown promising anticancer effect against sarcoma. Different parts of Alstonia scholaris have exhibited anticancer, antibacterial, and bronchodilatory activities in preclinical studies. Anticancer evidence for A. scholaris is at the in vitro and animal model level only. No experimental human clinical work has been conducted as of current reviews; published reviews characterize it as a promising natural source of anti-cancer agents but call for systematic pharmacological and toxicological studies.

4.5 Antimicrobial and Antiviral Activity

Total alkaloids extract (TA) from the leaves of A. scholaris inhibited herpes simplex virus type 1 (HSV-1), respiratory syncytial virus (RSV), and influenza A virus (H1N1) in vitro. The findings of antimicrobial activity studies of Alstonia scholaris validate its well-known traditional and ethnopharmacological uses in the treatment of infectious diseases; however, current studies are insufficient to establish Alstonia scholaris as an authentic antimicrobial agent.

4.6 Hepatoprotective Activity

The bark contains antioxidant properties and offers hepatoprotective benefits, making Alstonia scholaris a valuable resource in both traditional and modern medicine. Extract from A. scholaris containing high flavonoid and phenolic components has been investigated for preventing oxidative stress-mediated hepatic injuries. Evidence is preclinical (cell and animal level).

4.7 Antidiabetic Activity

The plant has been found to exhibit anti-diabetic properties; extracts from the leaves demonstrate significant hypoglycemic effects, indicating potential use in managing diabetes. This evidence is limited to preclinical/in vitro studies.

4.8 Antiviral Activity in the Context of COVID-19 (Ayush-64)

Researchers evaluated the efficacy of Ayush-64 (A64) — a polyherbal formulation containing Alstonia scholaris, Caesalpinia crista, Picrorhiza kurroa, and Swertia chirata — against COVID-19 in a Syrian hamster infection model. Preventative use of A64 resulted in late-phase recovery of body weight loss in SARS-CoV-2-infected hamsters, suppression of pro-inflammatory cytokines, and blunted pulmonary pathology. The hamster challenge data showed robust anti-viral and immunomodulatory potential in A. scholaris, followed by P. kurroa. Evidence is animal-model only for this application; the contribution of A. scholaris specifically within the multi-herb formulation to clinical outcomes in humans is not yet established.

4.9 Neuropathic Pain

The plant has afforded protection in various models of algesia and inflammation, including acetic acid-induced writhing, the formalin test, and the air pouch model in rodents. Traditional reports indicate the plant is useful in treating normal and rheumatic pains, and pharmacological reports indicate anti-inflammatory and analgesic activities. Evidence remains at the preclinical stage.

5. Body Systems and Health Areas of Association

• Respiratory system: Chronic bronchitis, asthma, COPD, whooping cough, tracheitis, post-infectious cough — the best-evidenced area in modern research.
• Immune and infectious disease: Malaria, antimicrobial, antiviral (HSV-1, RSV, H1N1, SARS-CoV-2 in animal models).
• Gastrointestinal system: Dysentery, diarrhoea, dyspepsia, abdominal disorders, ulcers.
• Integument (skin): Leprosy, chronic ulcers, cutaneous diseases; inhibition of MMP-1 and anti-irritant properties in dermatology-focused in vitro research.
• Musculoskeletal and pain: Rheumatism, analgesic effects against peripheral pain.
• Metabolic: Preclinical antidiabetic and hypolipidemic effects.
• Hepatic: Hepatoprotective and antioxidant effects.
• Oncology: In vitro and animal studies for anticancer activity, primarily against sarcoma and related models.
• Neurological: Preclinical evidence for nootropic, anti-stress, and neuroprotective effects.

6. Dosage Forms and Dosages Reported in Studies

The polyherbal formulation Ayush-64 contains aqueous extract of Saptaparna (Alstonia scholaris) 100 mg, Katuki (Picrorhiza kurroa) 100 mg, Kiratatikta (Swertia chirata) 100 mg, and powder of Kuberaksha (Caesalpinia crista) 200 mg — in the ratio of 1:1:1:2.

In the Phase I clinical trial of CALAS (Capsule of Alkaloids from A. scholaris leaves):

• Single ascending doses (SAD) tested were 8, 40, 120, 240, 360, and 480 mg; multiple ascending doses (MAD) tested were 40 or 120 mg three times daily for 7 days.
• The study supported safety up to a single dose of 360 mg and up to 120 mg three times daily for 7 days in healthy Chinese volunteers.

In the sub-chronic toxicity study in beagle dogs:

• After oral administration of a single dose of 4 g/kg body weight, a number of transient symptoms were observed but no treatment-related mortality; a sub-chronic toxicity study with doses of 20, 60, and 120 mg/kg body weight was conducted over a 13-week treatment period followed by a 4-week recovery observation.

In chronic toxicity tests in rats:

• In a chronic toxicity test, rats were continuously administered total alkaloids (TA) at doses of 50, 100, and 300 mg/kg body weight for 13 weeks; the non-observed-adverse-effect-level (NOAEL) of TA with daily oral administration to rats was determined to be 100 mg/kg body weight.

In sub-acute toxicity studies in Sprague-Dawley rats (stem bark methanolic extract):

• A single dose of 2000 mg/kg was administered via oral gavage for acute toxicity assessment; in the sub-acute study, rats received three doses of ASME — 250, 500, and 1000 mg/kg — for 28 days via oral gavage.

The leaf crude water extract is currently prepared commercially as a tablet or granule for the treatment of tracheitis and the common cold in China, though specific per-dose amounts for commercial preparations were not reported in accessed sources.

7. Safety Considerations

Acute Oral Toxicity

Oral administration of hydroalcoholic extract of A. scholaris was non-toxic up to a dose of 2000 mg/kg body weight, while the maximum number of animals succumbed to death after administration of 1100 mg/kg by the intraperitoneal route. In acute toxicity tests with total alkaloids (TA), a single administration at 12.8 g/kg body weight in mice produced prone position, shortness of breath, wheezing, and convulsion; the LD₅₀ in mice was 5.48 g/kg body weight, which is almost 2740 times the clinical dose in humans.

Sub-Acute and Chronic Toxicity (Hepatotoxicity Concern)

In sub-acute toxicity studies, significant variations in body weight, hematological, and biochemical parameters were observed in experimental groups at doses of 500 and 1000 mg/kg, with the death of two female rats recorded at the highest dose (1000 mg/kg body weight). Histopathological studies revealed slight degeneration and centrilobular necrosis in the liver, most expressed in the highest-dose group. While single dose and short-term oral intake of A. scholaris bark extract caused no toxicity up to 2000 mg/kg, toxic effects manifested in long-term treatment at the highest doses; the long-term toxic effect was associated with alterations in hematological compositions and end-organ damage to the liver. Thus, prolonged use of high doses is discouraged.

Developmental and Reproductive Toxicity

Administration of 360 and 480 mg/kg body weight of bark ethanol extract to pregnant Swiss albino mice resulted in congenital abnormalities such as syndactyly, bent tails, and developmental delays in newborn mice. Repeat-dose oral toxicity of the methanol extract of the bark was evaluated in Sprague-Dawley rats for 28 consecutive days; changes in hematological compositions and end-organ damage to the liver were observed at doses of 500 and 1000 mg/kg body weight.

Seasonal Variation in Toxicity

The acute toxicity in mice depended on the season of collection of the plant; the highest acute toxicity was observed in the extract prepared from the summer collection, followed by winter; the least toxicity was observed in the extract prepared from bark collected in the monsoon season. This finding has practical implications for standardization of preparations.

Clinical Trial Adverse Events

In the Phase I human trial of CALAS, 62 enrolled volunteers completed the study with no serious adverse events. Treatment-emergent adverse events (TEAEs) were reported in 23.91% of CALAS-treated subjects and 18.75% of the placebo group (p > 0.05); all TEAEs were mild, transient, and disappeared without intervention. TEAEs possibly related to CALAS treatment included hiccups (8%), dry mouth and nausea (6%), increased sleep (4%), abdominal distension (2%), and elevated bilirubin (2%).

Ayush-64 Safety Data

Ayush-64 has demonstrated safety and efficacy in infective febrile conditions and was found safe and non-toxic at a dose of 500 mg/kg body weight for 12 weeks in experimental studies. Pregnant and lactating mothers should take Ayush-64 only if prescribed; the safety of Ayush-64 is not established through scientific studies in pregnant and lactating women.

Adulteration Concern

In India, the bark of Alstonia macrophylla is sometimes used as a substitute for Alstonia scholaris bark in herbal pharmaceutical preparations. The use of Alstonia macrophylla as a substitute for Alstonia scholaris is not justifiable, as both species are distinct in their phytochemistry and pharmacology; further chemical fingerprinting and metabolic studies are warranted to prevent their mutual adulteration, most importantly in the context of commercial preparations.

Plant Toxicity Classification

The plant is inherently toxic but is used traditionally for myriad diseases and complaints. The rich alkaloid content, while responsible for pharmacological activity, is also responsible for dose-dependent toxicity effects observed in both animal and early human data. All current clinical evidence is limited to Phase I safety studies in healthy volunteers; large-scale efficacy and safety trials in disease populations have not yet been completed or published in the sources accessed.

References

• Wikipedia: Alstonia scholaris
• ScienceDirect Topics: Alstonia scholaris — Overview
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• ScienceDirect: Clinical population pharmacokinetics, metabolomics and therapeutic analysis of alkaloids from Alstonia scholaris leaves in acute bronchitis patients
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• PubMed: Pharmacological evaluation of Alstonia scholaris — anti-tussive, anti-asthmatic and expectorant activities (J Ethnopharmacol, 2010)
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• PubMed: Evaluation of Ayush-64 and Its Ingredients in the Syrian Hamster Model for SARS-CoV-2 Infection Reveals the Preventative Potential of Alstonia scholaris
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