thorny question

Guido Flamini flamini at FARM.UNIPI.IT
Thu May 18 08:04:33 CDT 2000

>Based on unintentional ramdom sampling, thorns of some shrubs must have a
>chemical associated with them because even a slight prick can cause pain
>that's more severe and longer lasting that pricks from other thorns.  It
>would be interesting to know if someone has examined potential irritants
>associated with thorns, whether or not these are unique to the thorns, and
>which species have the doubly whammy of chemical+thorn.

One of the most typical examples is Urtica (even if it is not a shrub) that
contains in its trichomes many irritating chemicals like histamine which is
injected to the browser causing an inflammatory (painful) reaction.

There are also many other complex defensive mechanisms that involve
particular chemicals. One example is furanocumarins (Ficus, many Apiaceae,
ecc) or polyacetylenes (many Asteraceae and Apiaceae again, among the
other) that become toxic after their exposition to sunlight (i.e. an
herbivorous damage), causing phototoxicity.

Guido Flamini

Dr. Guido Flamini
Dipartimento di Chimica Bioorganica e Biofarmacia
Via Bonanno 33, 56126 Pisa, Italia
Tel: +3905044074; Fax: +3905043321
e-mail: flamini at

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