lactucic acid

from The Century Dictionary.

• noun A bitter, acrid, brownish-green, amorphous compound obtained from the juice of Lactuca Canadensis.
• noun A light-yellow crystalline compound, C₄₀H₅₈O₁₁(?), formed by the action of dilute sulphuric acid on lactcuarium. It gives a wine-red color with alkalis.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry Any of various acids derived from the juice of Lactuca virosa.