S1 L1 Introduction to Pharmacognosy - PowerPoint PPT Presentation

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S1 L1 Introduction to Pharmacognosy

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To study the way the body responds to their pharmacological use ... Exist in range of structures that one wouldn't think of synthesizing ... – PowerPoint PPT presentation

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Title: S1 L1 Introduction to Pharmacognosy


1
S1 L1 Introduction to Pharmacognosy
  • Anna Drew
  • with slide contribution from Bob Hoffman
  • grateful acknowledgement for inspirational
    teaching received at the School of Pharmacy,
    University of London

2
  • Pharmacognosy
  • pharmakon a drug (Greek)
  • gignosco to acquire knowledge of (Greek)
  • OR cognosco to know about (Latin)
  • Johann Adam Schmidt (1759-1809)
  • Lehrbuch der Materia Medica
  • Published Vienna 1811
  • Beethovens physician

3
Naturally occurring substances having a medicinal
action
  • Surgical dressings prepared from natural fibres
  • Flavourings and suspending agents
  • Disintegrants
  • Filtering and support media
  • Other associated fields
  • Poisonous and hallucinogenic plants
  • Raw materials for production of oral
    contraceptives
  • Allergens
  • Herbicides and insecticides

4
Pharmacognosy is related to
  • Botany
  • Ethnobotany
  • Marine biology
  • Microbiology
  • Herbal medicine
  • Chemistry (phytochemistry)
  • Pharmacology
  • Pharmaceutics

5
Skills techniques valuable elsewhere
  • Analysis of other commodoties
  • Foods, spices, gums, perfumes, fabrics, cosmetics
  • Used by
  • Public analysts, forensic sciences,
    quality-control scientists
  • Role in pure sciences
  • Botany, plant taxonomy, phytochemistry
  • Botanists and chemists looking at
  • Chemical plant taxonomy, genetic/enzymatic
    studies involving 2y metabolites
  • Artificial and tissue culture
  • Effects of chemicals on plant metabolites
  • Induction of abnormal syntheses
  • Bioassay-guided isolation techniques

6
  • Vegetable drugs can be arranged for study
  • Alphabetical
  • Taxonomic
  • botanical classification
  • Morphological
  • Organised drugs leaves, flowers, fruit, seeds
    etc
  • Unorganised drugs extracts, gums, resins, oils
    etc
  • Pharmacological/therapeutic
  • Increasingly used with screening
  • Constituents of one drug may fall into several
    groups
  • Chemical/biogenetic
  • Constituents or biosynthetic pathways

7
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8
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9
Example
  • Linnaeus (1707-1778), Swedish biologist
  • Division Angiospermae
  • Class Dicotyledoneae
  • Subclass Sympetalae
  • Order Tubiflorae
  • Suborder Verbenineae
  • Family Labiatae (Lamiaceae)
  • Subfamily Stachydoideae
  • Tribe Satureieae
  • Genus Mentha
  • Species Mentha piperita Linnaeus (peppermint)
  • Varieties Mentha piperita var. officinalis Sole
    (White Peppermint) Mentha piperita var.
    vulgaris Sole (Black Peppermint)

10
Contribution of plants to medicine and pharmacy
  • 18th century drugs plant based
  • 19th century a range of drugs was isolated
  • 1805 morphine
  • 1817 emetine
  • 1819 strychnine
  • 1820 quinine
  • Famous plants/plant drugs?

11
Quinine
  • Cinchona bark, South American tree
  • Used by Incas dried bark ground and mixed with
    wine
  • First used in Rome in 1631
  • Extracted 1820
  • Large scale use 1850
  • Chemical synthesis 1944
  • Actual tree remains the most economic source

12
Belladonna -gt atropine
  • Anticholinergic
  • syndrome
  • Hot as hell
  • Blind as a bat
  • Red as a beet
  • Dry as a bone
  • Mad as a hatter

13
Physostigma venosumCalabar bean
14
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15
Efik People
16
Efik Law
  • Trial by ordeal
  • A suspected person is given 8 beans ground and
    added to water as a drink. If he is guilty, his
    mouth shakes and mucus comes from his nose. His
    innocence is proved if he lifts his right hand
    and then regurgitates (Simmons 1952)
  • Deadly esere
  • Administration of the Calabar bean
  • First observed by WF Daniell in 1840
  • Later described by Freeman 1846 in a
    Communication to the Ethnological Society of
    Edinburgh

17
Physostigmine or EserineFirst isolated in 1864
by Jobst Hesse
18
Taxol
  • Pacific Yew tree, Taxus brevifolia, bark
  • 1964 activity discovered at NCI
  • 1966 paclitaxel isolated
  • Mitotic inhibitor
  • interferes with normal microtubule growth during
    cell div
  • Used for cancer chemotherapy
  • lung, ovarian, breast, head neck, Kaposis
    sarcoma

19
  • 1969
  • 1200kg bark -gt 28kg crude extract -gt 10g pure
  • 1975 active in another in vitro assay
  • 1977 7000 pounds bark requested to make 600g
  • 1978 Mildly active in leukaemic mice
  • 1979 Horowitz unknown mechanism
  • involved stabilising of microtubules
  • 1980 20,000 pounds of bark needed
  • 1982 Animal studies completed

20
  • 1984 Phase I trials
  • 12,000 pounds for Phase II to go ahead
  • 1986 Phase II trials began
  • Recognised 60,000 pounds miniumum needed
  • Environmental concerns voiced
  • 1988
  • An effect in melanoma
  • RR of 30 refractory ovarian cases
  • Annual destruction of 360,000 trees to treat all
    US cases
  • 1989 NCI handed over to BMS
  • Agreed to find alternative production pathway
  • 1992 BMS given FDA approval 5yrs marketing
    rights
  • Trademark Taxol Generic paclitaxel
  • 2000 sales peaked US1.6 billion
  • Now available as generic

21
Alternative production
  • 1967-1993 all sourced from Pacific Yew
  • Late 1970s synthetic production from
    petrochemical-derived starting materials
  • 1981 Potier isolated 10-deacetylbaccitin from
    Taxus baccata needles
  • 1988 published semi-synthetic route
  • 1992 Holton patented improved process improving
    yield to 80
  • 1995 use of Pacific Yew stopped
  • Now plant cell fermentation (PCF) technology used
  • Also found in fungi
  • Race for synthetic production -gt docetaxel

22
Why do we need plants?
  • Source of drug molecules
  • Most drugs can be synthesised
  • Still more economical to use the plant
  • Papaver opium -gt morphine, codeine (strong
    medicinal pain)
  • Ergot fungus gt ergotamine (headache),
    ergometrine (direct action on uterine muscle)

23
Digitalis foxglove -gt digoxin (acts on cardiac
muscle)
24
  • 2. Source of complex molecules that can be
    modified to medicinal compounds
  • Examples
  • Droscera yam molecule -gt steroids
  • Soya saponins -gt steroids

25
  • 3. Source of toxic molecules
  • To study the way the body responds to their
    pharmacological use
  • Investigating pharmacological mechanisms
  • picrotoxin nerve conduction

26
4. Source of compounds to use as templates for
designing new drugs
Morphine No better painkiller. Once structure
worked out wanted to improve it. What is
required?
Diacetylmorphine (heroin) OH group -gt
O-O-diacetyl. Still addictive?
Codeine Methylate hydroxyl phenolic O-Me. 1/5
analgesic capacity of morphine, useful to
suppress cough reflex
Dihydromorphinone Reduced , oxidised 2y alc.
Potential analgesic.
27
Dihydrocodeine Me-ether of previous. More
powerful than codeine, less than morphine.
Dextromethorphan Good against cough reflex
Is lower ring necessary?
Is middle ring needed?
Pethidine
Pentazocin
Methadone
Phenazocine
28
  • 5. Source of novel structures
  • these might never be thought of
  • Catharanthus periwinkle -gt vincristine (alkaloid
    dimer)

29
  • 6. Source of plant drugs
  • As a powder or extract
  • The pure compound is often not isolated because
  • Active ingredient is unknown
  • Active ingredient is unstable
  • Isolation process is too costly

30
  • 250,-500,000 species of higher plants on earth
  • lt10 investigated and only for one activity
  • Huge potential in plant kingdom
  • Future intense screening
  • Anticancer - NCI
  • Antimicrobial
  • Antiviral
  • Antimalarial
  • Insecticidal
  • Hypoglycaemic
  • Cardiotonic
  • Antiprotozoal
  • Antifertility - WHO

31
  • Screening
  • Pharmacological in vitro testing
  • Chemical certain constituents Eg alkaloids
  • Failed screening work
  • Incorrect identification of plant material
  • Plants exist in chemical races different
    constituents
  • Low yield of active compound
  • Solubility have to find correct solvent

32
Future
  • 80 world population rely on natural remedies
  • Westernization of societies
  • (traditional knowledge)
  • Extermination of species
  • conservation, retain gene pools
  • Natural resources exhausted
  • cultivation, artificial propogation

33
Conclusion
  • Natural products very important to medicine
  • Exist in range of structures that one wouldnt
    think of synthesizing
  • Can act as templates for new drug development
  • Untapped reservoir of new compounds
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