ACMT Toxicology Visual Pearls – A Poke in the Belly

Answer: 5. Saponin glycosides

Discussion [1-7] 

Phytolacca americana<, also known as pokeweed, is a tall perennial with purple-red stems and berries in grape-like clusters found in the Midwest and Eastern North America.  The plant contains toxic compounds such as saponin glycosides (including phytolaccatoxin), a lectin called pokeweed mitogen, and a ribosomal inhibiting protein called pokeweed antiviral protein (PAP). The mature, deep purple berries are less toxic than immature berries.  The roots are the most toxic.  The leaves, stems, and berries are ingested as part of a salad or imbibed as tea. Historically, pokeweed has been purported to treat ailments such as rheumatoid arthritis, various forms of dermatitis, or as an emetic.  Some consumers parboil the plant components to avoid unwanted symptoms.

The saponin glycosides are the cause of gastrointestinal irritation with the ingestion of pokeweed.  Pokeweed mitogen is responsible for the hematologic abnormalities that can be seen following ingestion.  PAP does not seem to cause significant clinical effects in humans due to difficulty entering the cell membranes of higher animal forms.  However, PAP has been extracted for use as an antiviral agent due to its ability to remove purine groups from the rRNA of viruses, and for its possible antitumor capabilities, highlighting its potential pharmacological uses.

Clinical manifestations [2,3,5,9] 

• Symptoms typically begin within a half hour to six hours following ingestion and are often self-limited.
• Symptoms are more likely after ingestion of raw berries or leaves.
• Predominantly gastrointestinal symptoms are seen, ranging from self-limited gastroenteritis to severe hemorrhagic gastritis.
• Rarely, other clinical symptoms manifest including bradycardia, ventricular dysrhythmias, hypotension, sweating, weakness, incontinence, syncope, confusion, tremors, seizures, and encephalopathy.

Diagnostics and Management [2,3,5,10]

• Identification of the plant is useful for anticipatory guidance.
• Red-purple skin discoloration, particularly over the hands or perioral area, may indicate ingestion of pokeweed berries.
• Dark stool with negative fecal occult blood tests may be seen with ingestion.
• An atypical lymphocytosis may occur which typically resolves within ten days.
• Activated charcoal may limit toxin absorption in absence of contraindications.
• Supportive care consists of rehydration and symptom control.
• Central nervous system (CNS) hyperexcitation should be treated with benzodiazepines.
• Symptoms last up to 24 hours and may require prolonged observation.

Bedside pearls

• Saponin glycosides are the cause of gastrointestinal irritation with the ingestion of pokeweed.
• Patients may present with hypotension, weakness, cardiotoxicity, and CNS findings.
• Symptoms typically begin a half hour to six hours following ingestion of pokeweed and are often self-limited. Symptoms can last up to 24 hours.
• Activated charcoal may be considered in absence of contraindications.
• Supportive care is the mainstay of therapy.