Cycas revoluta 蘇鐵

POISONOUS PARTS

Seeds.³

TOXICITY

• Toxic Constituents

  β-Methylamino-L-alanine and cycasin.⁴

• Mechanism

  β-Methylamino-L-alanine acts as an agonist at glutamate receptors, leading to neuronal injury. Cycasin is metabolised by gut bacteria into a potent carcinogen methylazoxymethanol. The mechanisms of gastrointestinal toxicity remain unidentified for cycasin.^4–7

• Poisoning Features

  Nausea, vomiting, diarrhoea, abdominal pain, headache and dizziness. Parkinsonism-dementia complex has been linked to chronic consumption though it has been disputed.^5,8,9

CLINICAL MANAGEMENT

Supportive treatment.

IDENTIFICATION FEATURES

Trunks 2–8 m tall; bark grey-black, scaly. Leaves fascicled at apex of stem, 1-pinnate; petioles 10–20 cm long, with spines along each side; leaflets 60–150 pairs, leathery, 10–20 cm × 4–7 mm. Pollen cones 30–60 × 8–15 cm, microsporophylls 3.5–6 × 1.7–2.5 cm. Megasporophylls 14–22 cm long, densely tomentose; ovules densely pale brown tomentose. Seeds (3–)4–5 × 2.5–3.5 cm, orange to red.¹⁰

MEDICINAL USES

Uses in TCM—seeds: stanch bleeding with astringent, unblock the meridians, promote digestion, pacify the liver and reduce blood pressure, suppress cough and dispel phlegm; flowers: regulate qi and dispel dampness, activate blood and stanch bleeding; leaves: regulate qi and activate blood, resolve stasis and relieve pain, disperse swelling and remove toxin. Recommended dose: seeds 9–15 g, flowers 15–60 g, leaves 9–15 g.^2,11,12

CASES IN TRL

In 2009, a middle-aged man presented with severe vomiting, dizziness and abdominal pain after taking the seeds of C. revoluta. He improved with supportive treatment and was discharged the next day.

LABORATORY ANALYSIS

Cycasin can be detected by GC-FID. β-Methylamino-L-alanine can be detected by LC-MS/MS.^13,14