Abstract
Cnicin, a sesquiterpenlactone of germacranolide-type, reacts with polynitroaromatic
compounds in alkaline medium to form intensely coloured products of the Meisenheimer
complex-type. A propenide complex results from the addition of excess picrate (Baljet
reagent), which is stable enough for photometric cnicin determination. Dried leaves
of Cnicus benedictus L. (Blessed Thistle, Asteraceae) contain up to 2.5% of cnicin and commercial herbs
between 0.2-0.7%. Shoots and flowering heads are almost free from this bitter substance.
Storage of dried plant material leads to high losses due to the instability of cnicin.
The approximate acute toxicity (ALD50 ) for mice, orally administered, is 1.6-3.2 mmol cnicin/kg body weight. Cnicin shows
an antiinflammatory activity in the rat paw edema screen which is nearly equivalent
to that of indomethacin. Intraperitoneal application of cnicin results in a strong
irritation of tissue. In the writhing-test, cnicin causes abdominal pain in mice with
an ED50 of 6.2 µmol/kg body weight.
1 Teil der Dissertation von I. Lachner, Frankfurt a. M., 1984.
