Painful native plant may hold pain relief key
A scientist's painful brush with a New Zealand native plant has led to research that may help develop a new pain relief drug. Warren Gamble reports.
Eric Buenz was reaching for a deer he had shot in the Marlborough Sounds bush when he felt the sting.
"It was this crazy, burning sensation and I thought 'what the hell'."
A short time later his hand started to lose all feeling.
Some may have brushed off the painful and numbing encounter with New Zealand's native stinging nettle ongaonga.
But for Buenz, an American biomedical scientist, botanist and natural products expert who had recently moved to Nelson, it triggered his professional curiosity.
It has led him and his Nelson Marlborough Institute of Technology colleague, neurologist Professor Gareth Parry into an international project with the potential to provide new pain relief medication for those afflicted by debilitating conditions like diabetes.
Diabetics commonly suffer stabbing and burning pain from neuropathy – damage to peripheral nerves.
What particularly got Buenz's scientific senses tingling in the bush was not the sting from the poisonous spines of the ongaonga but the numbing aftermath. It's not common to get such an effect on the nervous system from a substance that is only applied to the skin.
"I can't think of anything else that's like that," Buenz said. "It's rare to find something that's so potentially powerful that hasn't been examined."
Buenz set out with Parry to see if they could identify the compounds responsible.
First, they needed a supply of ongaonga. With permission from the Department of Conservation, they harvested the native nettle from an area near the Riwaka resurgence and in the Kahurangi National Park.
Ongaonga, recognisable by its distinctive spiky leaves and covered with hair-like trichomes that secrete its poison, is more common in the North Island, but also grows in the West Coast of the South Island.
Through contacts at the prestigious Mayo Clinic in the United States, where he completed his doctorate in biomedical science, Buenz arranged for initial screening tests of the plant last month. The experiment added the extract of the plant to neurons grown in a laboratory dish. The results suggested the presence of an ingredient worth exploring further.
The next step is more detailed testing, including at a specialist natural products laboratory in the Netherlands, run by another colleague. There a molecular picture of the plant can be created and compared to a database of thousands of natural compounds.
The hope is that ongaonga contains an undiscovered ingredient that ultimately could be produced synthetically to replicate its numbing properties without the initial pain.
There is a long way to go, but the researchers are hopeful.
The Mayo Clinic's director of the Complementary and Integrative Medicine Programme, Brent Bauer, said plants had always been a source of new drugs, "but this nettle is one of the more promising plants I have seen".
Parry, professor emeritus at the University of Minnesota and a world authority on Guillain Barre syndrome, said the ongaonga toxin probably worked by binding to the nerve endings in the skin that moderated pain impulses.
He said the only other plant toxin with similar properties was capsaicin from the capsicum pepper plant, but experience suggested ongaonga was more toxic, and potentially more effective.
Such research does not come cheap, and the researchers have welcomed a $25,000 grant from the New Zealand Guillain Barre Syndrome Support Group NZ Trust. The syndrome is a rare disorder of the nervous system that causes pain and progressive muscle weakness. The grant will allow them to conduct further tests without having to rely on the goodwill of friends.
The project also has been undertaken in collaboration with the Wakatu Incorporation.
- A documentary on the ongaonga project, made by NMIT creative industries tutor Klaasz Breukel and freelance film-maker John Irwin, is an entry in the 180 Seconds of Science Competition.