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The pharmacologic activity - Knowledge of drugs or pharmaceuticals

(3)

The pharmacologic activity

: ( evaluation and standardization)Strength of the drug or its preparation by Assays on living animals (

in vivo

) as well as on intact or excised organs (

in vitro

). Because living organisms are used, the assays are called

biologic assays or bioassays.



  • 4-

    Chemical

    : For

    active constituents of many natural drugs ♠ activity

    • 4-

      Chemical

      : For

      active constituents of many natural drugs ♠ activity

    • ♠ Best methods of determining the official

      potency

      for crude drugs and their products
    • 5-

      Physical

      :
    • ♠ typical physical constants are rarely applied to crude drug.

    • ♠ But extensively applied to the active principles of drugs, such as alkaloids, volatile oils, an

    • others.



    The secondary constituents of drug plants are influenced

    • The secondary constituents of drug plants are influenced

    • → by 3 principal factors:

      • 1-

        Heredity

        (

        genetic composition

        ).
      • 2-Ontogeny (stage of development

        ).
      • 3-Environment.



    → induce both quantitative and qualitative changes,

    • → induce both quantitative and qualitative changes,

    • but

      those caused by environmental influences are primarily

      quantitative

      .
    • →Perhaps the best-known pharmacognostic examples of

      chemical races

      are found in the

      ergot fungus

      (Claviceps purpurea).
    • →Individual strains have been isolated representing chemical races that produce superior yields of single desired

      alkaloids

      , e.g.,

      ergotamine

    • → instead of the usual small concentrations of

      complex mixtures of

      alkaloids

      .


    also plays a significant role in the nature of the active constituents found in medicinal plants. Although it might be expected that the concentration of secondary metabolites would increase with the age of the plant.

    • also plays a significant role in the nature of the active constituents found in medicinal plants. Although it might be expected that the concentration of secondary metabolites would increase with the age of the plant.

    • →The canna

      bi

      diol content of Cannabis sativa reaches a peak early in the growing season
    • → then begins to decline.

    • →When this decline occurs → the concentration of

      tetra

      hydro

      cannabinol

      begins to increase and continues until the plant approaches maturity.
    • *→ In the opium poppy(Papaver somniferum), → the morphine content of the capsules is highest

      2 to 3 weeks after flowering

      .
    • →If the

      latex

      is harvested earlier, related alkaloids such as

      Theban and

      codeine

      predominate

      .
    • → On the other hand, if harvesting is

      delayed too long

      . The morphine → decomposes.




    Plant growth

    and

    developmen

    t, and often the

    nature

    and

    quantity of secondary metabolites

    , are

    affected

    • Plant growth

      and

      developmen

      t, and often the

      nature

      and

      quantity of secondary metabolites

      , are

      affected

    • →by

      temperature

      ,

      rainfall

      ,

      length of day

      (including the quality of light) and

      altitude

      .
    • Example : seeds of

      cannabis, grown ih England

      →and

      rich in CBD

      and devoid of THC, →

      when cultivated in Sudan

      started to

      produce THC

      in the first generation and in the second generation contained up to

      3.3% THC

      with a further decrease (down to 0% in some plants) of CBD.


    1- Temperature

    • 1- Temperature

    • →Temperature

      is a major factor controlling the development and metab­olism of plants.
    • → In general, the formation of

      volatile oils

      appears to be enhanced

      at higher

      temperatures, although very hot days may lead to an excess physical loss of oil. →The mean optimum temperature for

      nicotine production

      in Nicotiana rustica

      is 20°C

      (lower at 11-12°C and at 30°C).
    • fixed oils

      produced at

      low temperatures

      contain

      fatty acids with a

      higher content of double bonds

      than those formed at higher tempera­tures.


    2- Rainfall

    • 2- Rainfall

    • - The

      annual rainfall

      , its

      distribution

      throughout the year.
    • Continuous rain

      can lead to a loss of water-soluble substances from
    • leaves and roots by leaching; this is

      known

      to apply to

      some plants pro­ducing alkaloids, glycosides and even volatile oils

      . →This

      could

      account for

      low

      yields of some

      active constituents in wet seasons

      from plants whose general condition appears to be good.


    ?


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