Grayanotoxins

Grayanotoxins are a group of closely related toxins found in rhododendrons and other plants of the family Ericaceae. They can be found in honey made from their nectar and cause a very rare poisonous reaction called grayanotoxin poisoning, honey intoxication, or rhododendron poisoning. Grayanotoxin I (see below) is also known as andromedotoxin, acetylandromedol, rhodotoxin and asebotoxin; the systematic chemical name is: grayanotaxane-3,5,6,10,14,16-hexol 14-acetate. Grayanotoxins are named after Leucothoe grayana, a plant species from Japan, which is in turn named after 19th century American botanist Asa Gray.

Ac = acetyl

Grayanotoxins are polyhydroxylated cyclic diterpenes. They bind to specific sodium ion channels in cell membranes, the receptor sites involved in activation and inactivation. The grayanotoxin prevents inactivation, leaving excitable cells depolarized.

Poisoning from grayanotoxins is rarely fatal in humans, but can be lethal for other animals. Physical symptoms from grayanotoxin poisoning occur after a dose-dependent latent period of minutes to three hours or so. Initial symptoms are excessive salivation, perspiration, vomiting, dizziness, weakness and paresthesia in the extremities and around the mouth, low blood pressure and sinus bradycardia. In higher doses symptoms can include loss of coordination, severe and progressive muscular weakness, electrocardiographic changes of bundle branch block and/or ST-segment elevations as seen in ischemic myocardial threat,bradycardia (and, paradoxically, ventricular tachycardia), and nodal rhythm or Wolff-Parkinson-White syndrome. Despite the potential cardiac problems the condition is rarely fatal and generally lasts less than a day. Medical intervention is not often needed but sometimes atropine therapy, vasopressors and other agents are used to mitigate symptoms.

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