protopine

from The Century Dictionary.

• noun A crystalline alkaloid, C₂₀H₁₇O₅N, found in opium and in the roots of the celandine, Chelidonium majus, the bloodroot, Sanguinaria Canadensis, and Macleya cordata. It melts at 204° C. Also called macleyine.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) An alkaloid found in opium in small quantities, and extracted as a white crystalline substance.

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

• noun biochemistry A benzylisoquinoline alkaloid occurring in plants of the Papaveraceae family that acts as an opioid analgesic.