A potential therapeutic for chronic pain from the new zealand native stinging nettle urtica ferox (ongaonga)

Objectives Contact with Urtica ferox (ongaonga) causes an intense pain with subsequent sustained numbness. While all factors responsible for the initial painful response are known, the compound(s) responsible for the sustained numbness remain unidentified. There is a need for new therapeutics to treat chronic pain and the yet-to-be identified compounds in Urtica ferox may provide a novel topical treatment for chronic pain. Methods A collection expedition in Kahurangi National Park, New Zealand, was conducted. Urtica ferox trichomes were collected and a water extraction performed. Primary hippocampal neurons and NT2 cells were treated with extract to characterise toxicity. A small animal model was used to assess functional response to extract exposure. Results The extract of Urtica ferox induces a dose-dependent selective toxicity to neurons with morphologic characteristics of apoptosis. Evaluation of extract exposure in the small animal model suggest a direct and specific, effect on neurons. Preliminary characterisation of the active compound indicates a relatively small entity with phenolic ring structure. Conclusions Initial evaluations of the Urtica ferox extract indicate the presence of a compound(s) with promising characteristics. Specifically, a compound that selectively effects neurons that is small and water soluble. This unidentified compound will be characterised using metabolomics.