1. Lipids
Anna Drew
with grateful acknowledgement for inspirational teaching received at
The School of Pharmacy, University of London

2. LIPIDS Simple: fixed oils, fats, waxes
Complex: phosphatides, lecithins
may contain P, N as well as C, H, O
widely distributed in plant and animal kingdom
in all living cells
sometimes accumulate to be commercially useful
plants - food reserve (fruit and seeds)
animals – insulation, energy sources, protection
Lipids or ‘fatty esters’ are an important group
long chain fatty acid + alcohols eg glycerol

3. Fixed oils & fats Esters of glycerol:
3 fatty acids may be involved => triglyceride (main component of oils and fats)
some may exist as free acids
[Fish oils may have 12 fatty acids which vary]

4. Simple triglyceride (triacylglycerol)
all fatty acid groups the same
Mixed triglyceride
fatty acid groups different
more usual in nature
-> yields 3 molecules of palmatic acid

5. Saturated or unsaturated:
unsaturated acids: oleic, linoleic, linolenic, palmitolinic
saturated acids: palmitic, myristic, stearic
Fatty acid content determines properties
large amount of saturated -> solid at room temp.
large amount of unsaturated -> liquid at room temp.

6. Expect a good (fixed) oil to be:
most vegetable products contain a high number of triglycerides with unsaturated fatty acids – liquid
most animal products – opposite
where large number of unsaturated fatty acids readily oxidizes
eg whale, fish oils, linseed
Expect a good (fixed) oil to be:
odourless, tastleless and non-volatile
soluble in a lipid solvent
fairly readily air-oxidized -> rancid oil (depending on degree of saturation)
leave a permanent grease stain on filter paper

7. Determination of structure
by hydrolysis or saponification in 2 ways:
i) Alkaline hydrolysis with KOH
splits triacylglycerol into parent glycerol and releases all fatty acids
arrangement of fatty acids is unknown
ii) Can use an enzyme (pancreatic lipase)
hydrolyses two outer glycerides
and then remove final group with KOH
Detecting fatty acids
GLC – not volatile so have to form a methylether and separate them by chain length

8. Chemical tests solubility freezing point, melting point
refractive index (and sometimes optical rotation)
density
volatile acidity, unsaponifiable matter, acetyl value

9. Waxes contain appreciable quantities of
esters derived from higher monohydric alcohols (one –OH group) of the methyl (1y) alcohol series
combined with fatty acids (C16 – C32)
most are solids at room temperature
can only be saponified by alcoholic alkali
often contain free acids, hydrocarbons, free alcohols and sterols
saponification and acid values higher, iodine values lower
commercially important examples
Vegetable: carnuba
Animal: spermaceti, beeswax, ‘wool fat’

10. Uses readily absorbed through skin protect from entry of water
ointments
protect from entry of water
eg cod liver oil, linseed oil
vehicles for injections
waxes in enteric coatings
pharmacological substances
vitamin A and D in cod liver oil
food source
eg peanut oil
may contain essential fatty acids (linoleic acid, arachidonic acid required in prostaglandin formation)

11. Olive oil salad oil, sweet oil
From ripe fruits of Oleo europoea (Oleaceae)
Mediterranean, California
native of Palestine, known in Egypt in 7th century B.C., introduced into Spain early on
pale yellow with greenish tinge (chlorophyll and carotene)
bland, slight odour, goes “pasty”/cloudy at 10oC

12. high iodine value, low acid value Uses
tested for absence of arachis oil, cotton-seed oil, sesame oil, peanut oil and tea-seed oil (Camellia sasanqua)
Composition:
high iodine value, low acid value
Uses
salad oil, soaps, plasters
manufacture of parenteral preparations (low acid value, free of water)

13. Arachis oil From seeds of Arachis hypogaea (Leguminosae) - groundnut
cultivated in tropical Africa, India, Brazil, southern USA and Australia
world’s 4th largest source of a fixed oil
seeds contain 40-50% oil
fruits shelled by a machine
kernels difficult to express; crushed and ‘cooked’ at low pressure
seed cake fed to cattle

14. acid and saponification values similar to olive oil
Composition:
oleic acid ~ 60%
linoleic acid 24%
palmitic acid 9%
arachidonic acid
GU3, GSU2 like olive oil
acid and saponification values similar to olive oil
if fatty acids are separated (hydrolysis) the presence of arachidonic acid gives a melting point >710C
used as a test for adulteration of olive oil

15. Castor oil From seeds of Ricinus communis (Euphorbiaceae)
India, Africa, Europe
Contains ricinoleic acid 91%, glycerides GU3
must be free of ricin
pale yellow, very viscous, acrid tasting
soluble in ethanol (unlike most oils) due to so much hydroxy- acid
Used in toothpaste, nail varnish remover, lubricant industry and pharmacy (as derivatives)

16. Almond oil
From Prunus amygdalus v. amara (bitter – used in pharmacy), v. dulcis (sweet)
native to Far East, grown in Mediterranean, N.California
Oil is highly unsaturated
with oleic acid 77%, linoleic acid 17%
83% GU3, 17% GSU2
Bitter almond oil also contains amygdalin (glycoside) which decomposes to benazldehyde + HCN
Used in pharmacy in oily injections and ointments
prone to oxidation so has to be kept air-free or goes rancid – transfer to smaller bottle to exclude air

17. Theobroma oil Cocoa butter
From seeds of Theobroma cacao (Sterculaceaea)
Central America, also cultivated in Brazil, W.Africa (Nigeria)
Solid oil
high steric and palmitic acid content (35%, 25%), oleic acid 3%
GS2U 52%
melting point C
low iodine value because saturated
most expensive commercial fixed oil (adulterated)
Mainly used in suppositories

18. Animal products Cod and Halibut liver oils Beeswax
mixed triglycerides, mainly unsaturated C16-22 acids and decahexanoic acid
Used for Vitamin A and D content (halibut > cod)
Beeswax
yellow and white from honeycomb
simple esters of 1y alcohols with a high degree of myricyl palmitate (80%) (C15H31OOC30H61)
ester:acid ratio value
Used in paraffin ointment, plasters and enteric coating

19. Carnuba wax Spermaceti an adulterate of beeswax
From the cuticle of the South American palm Copenicia cerifera
Used in tablet coatings
Spermaceti
From the head of sperm (Physeter macrocephalus) and bottle-nosed whales (Hyperodon rostratus) just above right nostril) – 500lb from 1 whale
simple esters of cetyl alcohol CH3(CH2)4CH2OH – cetyl palmitate, cetyl myistate 90-93%
no longer used pharmaceutically, can be replaced by jojoba oil

20. Wool fat From the wool of sheep (Ovis aries) Complex composition:
esters of cholesteryl and isocholesteryl + estolidic 32-33%
esters of normal aliphatic alcohols with fatty acids 48-49%
Used as an emollient base for creams and ointments
major component of most ointments
melting point 30-42oC
readily absorbed through skin
absorbs twice its own weight in water so makes an emulsion

21. Extraction enzymes in cells can break down oils in cells
some oils highly unsaturated and easily oxidized – heat in air –> rapid oxidation
[1] Cold expression
[2] Steam treatment + expression
[3] Solvent extraction

22. [1] Cold method Castor beans Olives roll to break down testa
‘winnow’ to separate seed coat from seed
Olives
put into press
light pressure applied
gives the 1st grade oil used in pharmacy
oil washed to remove pigment
floats to the top and is skimmed off
30-40% oil recovered – not economical

23. [2] Steam treatment + expression
material left over from [1] undergoes steam treatment
repressed to get 2nd fraction of oil
[3] Solvent extraction
to get 100% of oil out
last portion gives a low grade used to industrial paints etc
left with high protein+fibre – fed to animals once ricin removed

24. Cocoa seeds Cod liver and halibut fat is solid so can’t cold express
use hot expression with steam treatment
oil is a byproduct of the cocoa industry
Cod liver and halibut
livers heated by steam process in an inert atmosphere
mixture separated by centrifugation
oil dried in drying towers
gives a clear bright highly refined oil
cooled to 0oC to remove saturated stearic fats
leaves polyunsaturated triglycerides
standardised for vitamin content
stored in airtight containers in the dark

25. Spermacetin Wool fat ensure well separated from normal triglycerides
washed with alkali
Wool fat
has to be cleaned up
acidified to precipitate waxes
free fatty acids removed by forming salts
wax extracted with acetate
product can be bleached to give light yellow colour or left as dark yellow wax

26. Volatile oils different from fixed components of plants that are
highly odiferous
generally occur as they are
secreted in oil cells in specialised structures
ducts, cavities, glandular hairs
frequently associated with other substances
gums, resins (resinify on exposure to air)
mainly terpenoid
some phenol ethers and phenols

27. Terpenoids based on the 5C isoprene unit Monoterpenes
most important, most volatile
di-, tri-, sesquiterpenes also important
contain 2 condensed 5C units head-tail
most formed from geranyl pyrophosphate

28. Monoterpene components
Hydrocarbons
Alcohols

29. Aldehydes
all produced via the terpenoid pathway
Ketones
Citral

30. Esters
Oxides

31. Sesquiterpenes (C15)
Hydrocarbons Phenols Phenolic esters
Anethole

32. Chemical and physical properties
volatile liquids with no colour
keep in amber bottles with minimum air
odour
asymetric centres, isomers with optical activity
only one isomer occurs naturally
refractive index normally high
is a means to characterise the oil
miscible in water and soluble in organic solvents
more soluble if contains –OH fatty acids
reasonably heat stable
can be steam distilled
tend to be used as solvents for resins

33. Families Economically only a few family groups are commercially useful
[1] Labiatae
Lavender, Mentha Sp.
large number, tend to hybridise
oil occurs in special organs
synthesized in glandular trichomes (mint)
burst easily releasing oil
[2] Umbelliferae
Fruits (best if ripe): anise, caraway, fennel, coriander
found in “vittae” in the outer layer is characteristic
steam distill to remove oils

34. [3] Pinaceae [4] Rutaceae [5] Lauraceae Pine, juniper Citrus fruits
found in resin ducts in outer old xylem or bark
released when bark removed
[4] Rutaceae
Citrus fruits
typical ductless sacs in outer part of fruit – rind
found at various depths before albino layer (white bitter pithy part)
oil is there under pressure and will burst open when ‘rasped’
less stable, need more care
[5] Lauraceae
Cinnamon, camphor
from region immediately below bark

35. Method of extraction depends where oils lies and its stability
Steam distillation
gentle, herb + water heated and oil distilled over
Water distillation
wood chips in chamber and heated until water distills over
crushed sample must be stable
Cold expression
citrus fruit oil (lemon, orange, bergamot)
rasping process breaks oil sacs in rind
pour cold water over and then separate oil and water

36. Destructive distillation
Enfleurage
petals (rose) placed between glass sheets covered in sheep or pig fat
oil seeps into fat and can be extracted with methanol
Destructive distillation
produces a different product from the one started with
pine and juniper heated to exclude air over
aqueous part - wood naphtha (ethanol and crude acetic acid) to attract juniper oil
non-aqueous part – resin (pine tar) to attract C5-C20 molecules including monoterpenes
like a fractional distillation
Menthol and camphor
nearly solid at room temperature
can isolate by freezing oils out
cheaper to synthesize camphor but generally extracted from plants
camphor

37. Uses [1] Flavours & carminatives Labiatae
as inhalations, orally, gargles, mouthwashes, trans-dermally
[1] Flavours & carminatives
Labiatae
Mentha piperita (peppermint oil)
50-75% menthol, also contains menthone etc
used mainly in toothpastes
Mentha spicata (spearmint oil)
50-75% L-carvone
some minor components similar to peppermint but major components differ giving different smell and taste
Lavendura officinalis (lavender oil)
35-45% linalyl acetate, also geraniol, limonene, cineole
some varieties have a lower % so other compound characteristics dominate
growing environment will affect quality

38. Rutaceae Umbelliferae Citrus oils Citrus flower oils
D-limonene 90%, citral 4% + esters, pinene, d-limonene (small amount)
high proportion of limonene desirable
but a lot is removed after isolation by distillation under reduced pressure
leaves oil high in citral which deteriorates on storage giving a turpentine odour
Citrus flower oils
no citral, other constituents that give a different odour and flavour of orange flower oil
used in confectionary
Umbelliferae
Pimpinella anisum (anise), Foeniculum vulgare (fennel)
90% anethole
some fennel variaties contain fenchone giving a bitter taste
Carum carvi (carraway)
carvone
Coriandum sativum (coriander)
60-80% linalool

39. [2] Local stimulants and antiseptics
(containing phenols)
Pinaceae
Pinus paulastrus
destructive distillation
phenol p-cresol
Juniperus oxycedrus
cadenine
Clove
Syzygium aromaticum
eugenol 82%
used on sore teeth to deaden pain
Eucalyptus oil
1,8-cineole 70%
(sesquiterpene)

40. [4] Insect repellant, antimating device
[3] Perfumes
Rose oil
Rosa gallica, R. damescena
trans-geraneol
and isomer cis-nerol
Lavender oil
Citrus oil
[4] Insect repellant, antimating device
Citronella oil
from grass
doesn’t work well
[5] Starting materials
Turpentine
(for synthesis of other compounds)