Alkaloids Alkaloids n n n Distribution Properties Role

Alkaloids

Alkaloids n n n Distribution Properties Role in plants q q Defense compounds Animal poisoning n n n q Lupine Groundsel Larkspur Jimson weed (Scopolamine) Henban (Atropine) Other roles in plants

Lupines Texas bluebonnet

Effects of alkaloids on humans n n High biological activity Produce varying degrees of physiological and psychological responses - largely by interfering with neurotransmitters q n n others interfere with membrane transport, protein synthesis or other processes In large doses - highly toxic - fatal In small doses, many have therapeutic value q muscle relaxants, tranquilizers, pain killers, mind altering drugs, chemotherapy

Psychoactive alkaloids n n n Although only a small percent are psychoactive, these get much focus Affect the central nervous system - often by influencing neurotransmitters Categories of psychoactive cmpds q q q n Stimulants Hallucinogens Depressants May also be narcotic (addictive)

Psychoactive alkaloids

Alkaloid synthesis n n n Most alkaloids are synthesized from a few common amino acids (tyrosine, tryptophan, ornithine or argenine, aspartic acid, & lysine) Nicotinic acid precursor for part of nicotine Purine precursor for caffeine Some alkaloids synthesized from terpenes - along mevalonic acid pathway Generally classified by the predominant ring structure and/or carbon skeleton

Tropane alkaloids Many of these psychoactive alkaloids

Pyrrolizidine alkaloids

Piperidine alkaloids

Piperidine/Pyridine alkaloids

Purine alkaloids Figure 3 -5 Caffeine

Quinoline alkaloids

Isoquinoline alkaloids

Indole alkaloids Vindoline Vinblastine (Catharanthus)

Quinolizidine alkaloids

Steroidal alkaloids

Steroidal alkaloids

Diterpenoid alkaloids

Amine alkaloids Alkaloids without heterocyclic nitrogen atoms

Other classes of alkaloids n n n Betalain alkaloids - pigment alkaloids Lycopodium alkaloids - restricted to club mosses Peptide alkaloids