Essential oils (PowerPoint)

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					Laboratory Classes
            Overall aims of the course
   Acquaint the pharmacy student with the chemistry
    and biological activity of two major groups of natural
    products, namely alkaloids and volatile oils. Also,
    semi-synthetic derivatives and synthetic analogues
    based on natural product templates of theses groups
    are covered.
   Give the student knowledge and practical experience
    in testing and quantification of selected groups of
    alkaloids and volatile oils.
Intended Learning Outcomes of The Course

   On completion of the module, the student will be
    able to:
   Understand and explain the chemistry of several
    groups of alkaloids and volatile oils, having
    knowledge of their structures, botanical
    occurrence, extraction, isolation, identification
    and determination procedures.
   Describe the biosynthesis and the therapeutic
    effects of different alkaloids and volatile oils.
Essential oils, Volatile Oils, Ethereal oils

   Definition
   Difference from fixed oils
   Distribution, localization and function
   Uses
   Physical characters
   Methods of preparation
   Quality control
   Storage
   Chemistry
   Classification
   Hydrocarbons, alcohols, phenols,………
Volatile Oils, Essential oils, Ethereal oils

   Oily liquids, which are entirely or almost entirely
    volatile without decomposition
   Plant products, giving the odors and tastes
    characteristic of the particular plant, thus
    possessing the essence.
   Ether like in their volatility.
  Mostly present as such, in some cases the essential oils
   don’t pre-exist but formed by decomposition of a
-Bezaldehyde (amygdalin)
 in bitter almond

                         -Allyl isothiocyanate (sinigrin)
                                        in black mustard
  Form a large and structurally diverse family
  of natural products derived from C5 isoprene units
  joined in a head to tail fashion
        CH3                                          tail

  H2C   C     CH   CH2
    1   2     3     4
                                     Isoprene unit
                   Isoprene              C5

The biologically active isoprene units were identified as
the pyrophosphate esters IPP (Isopentenyl pyrophosphate)
And DMAPP (Dimethylallyl pyrophosphate)
 Origin of terpenes                  Mevalonic acid

                      OPP                             OPP

                DMAPP (C5)                       IPP (C5)           Hemiterpenes (C5)

    GPP (C10)                                               Monoterpens & Iridoids (C10)


    FPP (C15)                                   OPP             Sesquiterpenes (C15)

                                                                  Diterpenes (C20)
 GGPP (C20)

2 x FPP   squalene          Triterpenes (C30)
                                                  2 x GGPP            Tetraterpens (C40)

                                         Steroids (C18-C30)
                                  Regular monoterpenes (essential oils,
                                  oleoresins, iridoids)
   C10-Monoterpenes
                                   Irregular monoterpenes (pyrethrins)

   C15-Sesquiterpenes (essential oils, sesquiterpenoid
   C20-Diterpens (e.g. retinol)
   C30-Triterpens & steroids (saponins, cardiac glycosides)
   C40-tetraterpenes (e.g. b-carotenes)
                         Regular monoterpene skeleton


        Iridane           Iridoid               Menthol       myrcene

  The iridan skeleton found in iridoids is
  monoterpenoid in origin and contains a
  cyclopentane ring which is usually fused
  To a six-membered oxygen heterocycle
                                             Irregular monoterpene skeletons
 Comparison between fixed oils and
          essential oils

 Their volatility
 When smeared on paper

 Oxidation (resinified, fixed oil rancid).

 Chemical structure

 Saponification by KOH (NOT saponify)
       Distribution, localization and function
 Distribution
 In higher plants, different families as: Rutaceae,
  Myrtaceae, Lamiaceae (Labiatae), Lauraceae,…..
 Accumulate in all types of vegetable organs:

Flowers (rose), Leaves (eucalyptus), Barks (cinnamon),
Woods (Sandalwood),          Roots (vitiver.),

Rhizomes (ginger),         Fruits (star anise),   Seeds (nutmeg).

   May occur associated with other constituents: gums
    (oleogums), resins (oleoresins) gums & resins (oleogumresins)
Usually in specialized
  histological structures
 Oil cells: Lauraceae,
 Glandular trichomes:
 Secretory cavities:
  Rutaceae, Myrtaceae
 Secretory canals:
  Apiaceae (Umbelliferae)
 Function
 Attracting (help polination) or repelling insects
 Protection from heat or cold

 As antibacterial agents

 Uses

 Pharmacy, aromatherapy

 Perfumery

 Food technology
           Physical properties
 Possess characteristic odors
 Liquids and volatile at ambient temp.
 Soluble in common organic solvents. Sparingly
  soluble in water, however sufficient to produce
  aromatic water.
 Specific gravity (0.8-1.17), mostly lighter than
  water (clove and cinnamon are heavier).
 Have high refractive index and most of them
  rotate the plane of polarized light.
            Good Laboratory Practice

 Safety spectacles (glasses) must be
 worn at all times in the laboratory.
 All reagents must be used with care as
they have a number of inherent dangers.
      Good Laboratory Practice
 Gloves must be worn when indicated
 All bottles must be kept in their places and tops
  on the bottles should be replaced immediately
  after use, to avoid spillage.
        Good Laboratory Practice
  Flammable solvents
and corrosive solutions
(all strong acids, aqueous
and ethanolic potassium
and sodium hydroxides,…)
are kept in the
fume cupboard and must
only be used in this area
          Good Laboratory Practice

   Solutions spilt on the skin should be removed
    initially by thorough washing of the area in cold
    running water. Any severe reaction should be
    reported at once to the staff in charge.
            Lab. 1 (Volatile oils)
I- Qualitative tests: Menthol, Thymol, Eugenol, Vanillin,
     Methyl salicylate
    Menthol
    0.5 ml of oil solution in a clean test tube + 2 drops
     of (1%) aq. FeCl3            –Ve (Yellow color).
    0.5 ml of oil solution in a clean porcelain dish
     W.B residue, dissolve in drops of Conc. H2SO4
     + drops of vanillin/H2SO4                orange yellow
     dps of H2O Reddish violet color.
    Special test for thymol gives –ve result
 Thymol
 0.5 ml of oil solution in a clean test tube + 2
  drops of (1%) aq. FeCl3          + Ve (Green
 0.5 ml of oil solution in a clean porcelain dish
  W.B       residue, dissolve in 0.5 ml of glacial
  acetic acid + dps of Conc. H2SO4 + dps of
  Conc. HNO3            Bluish green color.
N.B. This test is –ve for menthol.
 Eugenol
 0.5 ml of oil solution in a clean test tube   CH CH
                                                 2      CH2

+ 2drops of (1%) aq. FeCl3           + Ve (Green
 0.5 ml of oil solution in a clean test tube + 2
  drops of (2%) alc. FeCl3         Green to bluish
  green color.
 0.5 ml of oil solution in a clean test tube + 2
  drops of aq. saturated FeCl3        Green color +
  2 ml H2O            turbid brown.

 Vanillin                                      OH

 0.5 ml of oil solution in a clean test tube + 2
  drops of (1%) aq. FeCl3         + Ve (Blue to
  dark blue color).
 Methyl salicylate

 0.5 ml of oil solution in a clean test tube + 2
  drops of (1%) aq. FeCl3        + Ve (Violet color).
N.B. DON’T leave the oil on W.B too much,
  when making a residue.                      COOCH
          Scheme for Volatile oils
   0.5 ml of the oil unknown in a clean test tube +
    2 drops of (1%) aq. FeCl3

Yellow color     Green color      Dark blue color
                             Violet color
Menthol                                   Vanillin
                            Methyl salicylate
            Thymol        Eugenol
       II-Quantitative determination
         Determination of Aldehydes in
                  volatile oils
 Example: Cinnamic aldehyde in Cinnamon oil
Cinnamon oil (E.P) should contain not less than 50%
  and not more than 70% w/w of cinnamic aldehyde.
 Principle of assay:
R.CHO+NH2OH.HCl             R- CH=NOH+ H2O+HCl
The liberated equivalent amount of HCl is titrated
 against standard alkali.                CHO
   Pipette 5 ml of cinnamon oil into stoppered
    flask, add 10 ml of hydroxyl amine.HCl and
    shake well.
   Add 2-3 drops of methyl orange indicator, the
    solution is colored red.
   Shake and neutralize the liberated HCl with
    N/2 KOH until the red color changes to
    yellow color and the yellow color must be
    permanent after shaking vigorously for 2 min.
   Calculate the %w/w of aldehyde
   % of cinnamic aldehyde = E.P X 0.066032   X 1.008 X 100
                                   wt of the oil in gm
wt of the oil = 7.7 gm
0.066032 is the equivalence
1.008 is a correction factor
 Comment on the oil percent and its acceptance