Which of the following anticholinesterase is derived from a natural source?: (A) Physostigmine, (B) Neostigmine, (C) Pyridostigmine, (D) Tacrine
Answer is A. Ref: KD Tripathi pharmacology 7th edition (page.no: 108) Physostigmine is a Natural alkaloid from Physostigma venenosum (Calabar bean) and All others are synthetic Physostigmine is a highly toxic parasympathomimetic alkaloid, specifically, a reversible cholinesterase inhibitor