Identification of oxalic acid and tartaric acid as major persistent pain-inducing toxins in the stinging hairs of the nettle, Urtica thunbergiana.

Publisher: Oxford University Press Country of Publication: England NLM ID: 0372347 Publication Model: Print-Electronic Cited Medium: Print ISSN: 0305-7364 (Print) Linking ISSN: 03057364 NLM ISO Abbreviation: Ann Bot Subsets: MEDLINE

Publication: 2002- : Oxford, UK : Oxford University Press
Original Publication: Oxford [etc.]

Oxalic Acid/*toxicity ; Pain/*chemically induced ; Tartrates/*toxicity ; Urticaceae/*chemistry; Animals ; Chromatography, High Pressure Liquid ; Female ; Oxalic Acid/analysis ; Oxalic Acid/isolation & purification ; Pain Measurement ; Plants, Toxic/chemistry ; Plants, Toxic/metabolism ; Rats ; Rats, Wistar ; Tartrates/analysis ; Tartrates/isolation & purification ; Toxins, Biological/analysis ; Toxins, Biological/isolation & purification ; Toxins, Biological/toxicity ; Urticaceae/metabolism

Background and Aims: Once human skin contacts stinging hairs of Urtica spp. (stinging nettles), the irritant is released and produces pain, wheals or a stinging sensation which may last for >12 h. However, the existence of pain-inducing toxins in the stinging hairs of Urtica thunbergiana has never been systematically demonstrated. Experiments were therefore conducted to identify the persistent pain-inducing agents in the stinging hairs of U. thunbergiana.
Methods: The stinging hairs of U. thunbergiana were removed and immersed in deionized water. After centrifugation, the clear supernatants were then subjected to high-performance liquid chromatography (HPLC), enzymatic analysis and/or behavioural bioassays.
Key Results: The HPLC results showed that the major constituents in the stinging hairs of U. thunbergiana were histamine, oxalic acid and tartaric acid. However, the well-recognized pain-inducing agents, serotonin and formic acid, existed at a low concentration as estimated by HPLC and/or enzymatic analyses. The behavioural tests showed that 2% oxalic acid and 10% tartaric acid dramatically elicited persistent pain sensations in rats. In contrast, 10% formic acid and 2% serotonin only elicited moderate pain sensation in the first 10 min. Moreover, no significant pain-related behavioural response was observed after injecting 10% acetylcholine and histamine in rats.
Conclusions: Oxalic acid and tartaric acid were identified, for the first time, as major long-lasting pain-inducing toxins in the stinging hairs of U. thunbergiana. The general view that formic acid, histamine and serotonin are the pain-inducing agents in the stinging hairs of U. dioica may require updating, since their concentrations in U. thunbergiana were too low to induce significant pain sensation in behavioural bioassays.

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0 (Tartrates)
0 (Toxins, Biological)
9E7R5L6H31 (Oxalic Acid)
W4888I119H (tartaric acid)

Date Created: 20060506 Date Completed: 20060822 Latest Revision: 20220309

20231215

PMC2803540

10.1093/aob/mcl089

16675601