Alkaloids

Alkaloids

Distribution Properties Role in plants

Defense compounds Animal poisoning

Lupine Groundsel Larkspur Jimson weed (Scopolamine) Henban (Atropine)

Other roles in plants

Lupines

Texas bluebonnet

Effects of alkaloids on humans

High biological activity Produce varying degrees of physiological and

psychological responses - largely by interfering with neurotransmitters others interfere with membrane transport, protein synthesis

or other processes In large doses - highly toxic - fatal In small doses, many have therapeutic value

muscle relaxants, tranquilizers, pain killers, mind altering drugs, chemotherapy

Psychoactive alkaloids

Although only a small percent are psychoactive, these get much focus

Affect the central nervous system - often by influencing neurotransmitters

Categories of psychoactive cmpds Stimulants Hallucinogens Depressants

May also be narcotic (addictive)

Psychoactive alkaloids

Stimulants Hallucinogens DepressantsCocaine Tropane alkaloids Morphine

Ephedrine Mescaline Codeine

Caffeine Psilocybin Heroin

Ergot alkaloids (LSD)

Alkaloid synthesis

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

Betalain alkaloids - pigment alkaloids Lycopodium alkaloids - restricted to club

mosses Peptide alkaloids