<prompt> Which of the following anticholinesterase is derived from a natural source?PhysostigmineNeostigminePyridostigmineTacrine  <response>: 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 