(n.) An alkaloid found in opium in small quantities, and extracted as a white crystalline substance.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). Protopine. Retrieved September 21, 2026, from http://smartdefine.org/protopine/definitions/2050252 |
| Chicago | Webster's. 2011. "Protopine" http://smartdefine.org/protopine/definitions/2050252 (accessed September 21, 2026). |
| Harvard | Webster's 2011, Protopine, Smart Define, viewed 21 September, 2026, <http://smartdefine.org/protopine/definitions/2050252>. |
| MLA | Webster's. "Protopine" 27 May 2011. Web. 21 September 2026. <http://smartdefine.org/protopine/definitions/2050252> |