Alocasia macrorrhizos 海芋

Araceae 天南星科

Giant Alocasia, Alocasia¹

野芋、痕芋頭、廣東狼毒、觀音蓮、姑婆芋^2,3

POISONOUS PARTS

Whole plant.⁴

TOXICITY

Toxic Constituents
Calcium oxalate raphides, sapotoxins and other unidentified toxins.^5,6
Toxic Dose
Small amount of sap can cause local symptoms.
Mechanism
The toxic mechanism of the poisonous plants in the Araceae family is not fully understood. Calcium oxalate raphides stored in specialized cells known as idioblasts are released when subjected to mechanical pressure such as ingestion and contact, causing tissue irritation and inflammation. Other toxic ingredients that are commonly found in the family, such as sapotoxins and cyanogenic glycosides, may also play a role.^7–9
Poisoning Features
Skin contact with sap: itchiness. Eye contact with sap: may cause blindness. Ingestion: burning sensation of the tongue, oral cavity and stomach, salivation, nausea, vomiting, diarrhoea, dysphagia, dysphonia; convulsion, airway obstruction and death in severe cases.^5,6
Poisoning Events
Over 8 years, 27 cases of A. macrorrhizos poisoning have been reported in Taiwan. Most were related to ingestion and all recovered after supportive treatment.⁶

CLINICAL MANAGEMENT

Supportive treatment. Maintenance of airway by intubation or tracheostomy may be required for severe cases with airway compromise.^10,11

IDENTIFICATION FEATURES

Large perennial evergreen herbs, up to 3 m tall, caulescent stock unbranched, up to 15 cm thick, not stoloniferous. Petioles 0.5–2(–3) m long; leaf blades 50–100 × 40–100 cm, base sagittate, lateral veins 9–12 pairs. Peduncles 2–3 together, 12–60 cm long; spathe tubes 5–9 cm long, limb 10–20 cm long, spadix with terminal appendage. Berries 8–10 mm in diameter, red when ripe.¹²

MEDICINAL USES

Rhizomes or stems used in TCM: clear heat and remove toxin. Recommended dose: 3–9 g.^2,13

CASES IN TRL

In 2005, a man ingested boiled wild “taro” collected in the countryside. He presented with lip and throat swelling, epigastric pain and chest discomfort. He recovered with supportive care. In the tuber specimen (photo A), large amount of calcium oxalate raphides (photo B) were detected, compatible with A. macrorrhizos. There was another case in 2006. In the “taro” specimen (photo C), numerous calcium oxalate raphides (photo D) were also detected.