Alkaloids ● Limited taxonomic distribution ○ in plants ○ Not all plants makes alkaloids ■ Only 20% of plant flowering plant ■ mostly tropical ● less than 12000 known structures some are unique on… ○ Families ○ Genera ○ within individual species ■ Specific enzymes required for subclasses only found in limited species ● Biologically active ● Affect CNS of animals ○ Antifeedants(bitter,toxic) ○ Poisons Pharmacological/Biological activity observed as agonist or antagonist of… ● Depolarization in membrane ● Voltage gated Ca+2 channel ● Vesicle released from neurotransmitter ● Synaptic gaps ● Interaction in neurotransmitter and receptor ● Hydrolysis ● Reuptake of neurotransmitter E.g) Atropine ● Present in 0.2%-0.8% dry weight ● Mydriatic(dilating pupils) ● Anticholinergic(antagonist) ● Competes for muscarinic sites in PNS with acetylcholine ● Prevents passage of nerve impulse ● Motion sickness Alkaloids Biosynthesis ● Categorized into two main types ○ Based on origin of Nitrogen ■ Alkaloids from amino acids or other N-containing metabolites ■ Alkaloids from amination reaction Alkaloid Biosynthesis ● Complete biosynthesis of most alkaloids remains unknown ○ Morphine biosynthesis ■ Last two enzyme has just been characterized ■ Thebaine-6-O-demethylase(T6ODM) ■ Codeine-O-demethylase(CODM) ● Biosynthesis characterized by… ○ Stereo, regio-slelctive reaction ○ N-based chemistry ● Biosynthesis is oftenly tissue specific ○ integrates multiple tissue types