Alkaloids

1. Alkaloids

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

3. Lupines Texas bluebonnet

4. 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

5. 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)

6. Psychoactive alkaloids

7. 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

10. Tropane alkaloids Many of these psychoactive alkaloids

11. Pyrrolizidine alkaloids

12. Piperidine alkaloids

13. Piperidine/Pyridine alkaloids

14. Purine alkaloids Figure 3-5 Caffeine

15. Quinoline alkaloids

16. Isoquinoline alkaloids

17. Indole alkaloids Vindoline Vinblastine (Catharanthus)

18. Quinolizidine alkaloids

19. Steroidal alkaloids

20. Steroidal alkaloids

21. Diterpenoid alkaloids

22. Amine alkaloids Alkaloids without heterocyclic nitrogen atoms

23. Other classes of alkaloids • Betalain alkaloids - pigment alkaloids • Lycopodium alkaloids - restricted to club mosses • Peptide alkaloids