Antidote to fish toxin isolated from local plant

[CEBU, PHILIPPINES] Scientists are improving a Pacific folk remedy used to treat a form of food poisoning that prevents millions of people in the region from consuming fish.

'Octopus bush' (Heliotropium foertherianum) is the traditional medicine of choice in the Pacific islands for ciguatera fish poisoning which is caused by powerful ciguatoxins produced by microscopic Gambierdiscus algae.

Ingested by fish and clams, the toxins accumulate in the food chain, causing diarrhoea, vomiting and neurological symptoms in those who eat it. At least 100,000 people, mostly in the Pacific, are poisoned each year.

Scientists from the Institute of Research for Development (IRD), collaborating with colleagues from the Louis Malarde Institute in French Polynesia and Pasteur Institute in New Caledonia, Melanesia, screened around 100 medicinal plants for their activity against ciguatoxins.

Octopus bush extracts were found to be the most promising, containing a molecule similar to rosmarinic acid — a compound known for its antiviral, antibacterial, antioxidant and anti-inflammatory properties.

The researchers think rosmarinic acid may remove the ciguatoxins from their sites of action, as well as being an anti-inflammatory.

They are now seeking to patent rosmarinic acid and its derivatives, and are developing octopus bush extracts with an even stronger detoxifying effect.

Lead researcher Dominique Laurent of the IRD in French Polynesia said that Japanese research has suggested that octopus bush may contain alkaloids, naturally occurring chemicals that can be toxic. Fear of poisoning from the remedy may be deterring people from using it and a detoxified version might be more acceptable to local people, he said.

"We prefer to improve the folk remedy because it could be difficult to explain to local populations to buy a drug rather than use a plant growing on the beach," he said.

But the researchers have yet to consider how they would commercialise such a drug, said Laurent.

The poisoning is rarely fatal but the neurological symptoms can last several years. Fear of poisoning has reduced fish consumption, and the resulting dietary shift could lead to higher rates of cardiovascular disease, obesity and diabetes.

Paul Bienfang, a specialist in diagnosing algal toxins in fish, at the University of Hawaii, said the development of an effective antidote would be a significant accomplishment. "Effectiveness of an agent such as is described would mitigate the onset of neurological symptoms as well as the potential for prolonged discomfort by the victims," he told SciDev.Net.