Lipids Flashcards
what are lipids (3)
- organic polar, hydrophobic compunds
- esters of fatty acids and an alcohol
- simple or complex types
simple lipids include (3)
- glycerol fixed oils (fats)
- long chain monohydric waxes
- sterol based waxes
complex lipids are associated with these organs (5)
- heart muscle
- myelin sheath
- brain tissue
- cell membranes
- skin
complex lipids are classified as (3)
- phosphoglycerides
- glycolipids
- sphingolipids
the majority of pharmaceutically important lipds are simple or complex?
simple
fixed oils/fats differ from alkaloids, glycosides, and terpenes as they are
primary metabolites
why are fats necessary (3)
- great nutritional value
- concentrated reserve of energy
- dietary source of essential fatty acids which are precursors for prostaglandins
sources of fixed oils (2)/fats(1) include
Fixed Oils
- oil seeds
- animal sources
- cod
- halibut
- shark
Fats
- animals
- pig (lard)
- beef (tallow)
- sheep (suet)
isolation of oils from vegetable sources includes these 2 processes
- hot and cold expression
- cold expression yields purer oils e.g. virgin olive oil
hot expression process involves
- screening of seeds to remove debris
- magenet removes iron
- pass through steel rollers, cook meal 70-100C to rupture cells
- force through archimedian screw press
- high pressure yields low quality oil but higher extraction yield
- low pressure higher quality oil, less yield
- seed cake from low pressure can be further extracted using solvent extraction
which oils require further refinement
hot pressed
which type of extraction low or high pressure are used in pharma
low pressure because purer
oils/fats from animal sources are isolated by
wet rendering
describe the wet rendering process
- chunks of animal material into SS tank
- jacketed cyclinders in tank release steam under pressure through biomass
- oil cells break open, liquid/fat floats to surface, water/waste settles below
- draw off supernatant periodically
why is it important that fresh livers free of gall bladder are used for cod liver oil
because lipases in old livers would cause decomposition of the oils
why is refinement of hot pressed oils required to remove (7)
- free fatty acids
- reduce triglycerides
- remove pigments,
- oxidation products
- waxes,
- odors
- proteins
what are 4 methods of refinement
- neutralization with alkali
- removes free fatty acids
- bleaching
- removes pigments
- deoderizing
- remove odors
- winterizing
- chilling to 0C to remove solid fats or waxes
true fats are_________at normal room temp, while fats are _________at room temp
- liquid
- also known as fixed oils
- solid or semi-solid
all fats and fixed oils are chemically classified as ________and when combined with varying amounts of glycerol are known as_______
- glycerides of fatty acids
- monoglycerides, diglycerides or triglycerides
what is the major constituent of undecomposed true fats
triglycerides
for triglycerides when the three functional groups are the same they are considered simple or complex lipids, is this common?
- simple
- no most are mixed triglycerides
triglycerides of short chained saturated or unsaturated fatty acids are liquid or solid at room temp and predominate in fixed oils or fats
triglycerides of short chained saturated or unsaturated fatty acids are liquid at room temp and predominate in fixed oils
triglycerides of long chained fatty acids are liquid or solid at room temp and predominate in fixed oils or fats
triglycerides of long chained fatty acids are solid at room temp and predominate in fats
what is the controlling factor of triglyceride levels in plants and animals
- Plants - temperature
- Animals - diet
fatty acids that are common in plants and animals contain (4)
- even number of carbons
- straight chain
- terminal COOH
- fully saturated or up to 6 dble bonds
saturated fatty acids
have no double bonds
unsaturated fatty acids
- have varying degrees of double bonds up to 6
- generally cis configuration
- those in trans may be damaging to biological system
saturated fatty acids contain this at the end of the name
“OIC”
naming convention includes these two elements
- trivial name
- source
- systematic name
- number of saturated hydrocarbons with same number of carbon atoms
what does the shorthand designation relate to for saturated fatty acids e.g. 4:0
- number of carbon atoms: number of double bonds
the systematic naming convention for unstaturated fatty acids includes adding the following endings before the terminal “oic”. what do these relate to
- en
- dien
- trien
- number of double bonds
what are the pharmaceutical uses of fixed oils and fats (6)
- nutritive/dietary supplement - Almond, cod liver, coconut
- emollient - almond, olive
- solvent for injections - sesame, almond
- purgative - castor oil
- ointment base - coconut
- suppository base - theobroma oil
why are polyunsaturated fatty acids (liquid fixed oils) included in the diet, and what are they are treatment for?
- rich source of linoleic, linolenic and arahidonic essential fatty acids
- precursors for prostaglandins
- treatment of coronary heart disease, high cholesterol, atherosclerosis
what are two differences between fixed oils and volatile oils
- cannot be distilled without decomposition
- volatile oils predominantly separated using distillation
- leave a permanent greasy stain on paper
- volatile oils evaporate
what are general properties of fixed oils/fats (5)
- can’t be distilled without decomposition
- leave permanent greasy stain on paper
- insoluble in water, but soluble in most organic solvents except alcohol
- relative density <1
- sticky and greasy to touch
what are 3 challenges with the standardization of fixed oils and fats
- wide natural variation
- expesive oils susceptible to adulteration with cheaper oils
- estimation of single constituent does not indicate quality or purity
what should standardization of fixed oils focus on (4)
- physical measurements
- melting point
- relative density
- refractive index
- solubility
- qualitative or limit tests for oils likely to be used as adulterants
- chemical constants
- acid, iodine values
- chromatography
- TLC, GC
what is acid value a measure of
- the amount of free fatty acids present in the oil
- indicative of whether hydrolysis or decompostion of the oil has occurred
what is iodine value a measure of
- indication of amount of unsaturation where drying oils have large iodine values
- classifies the oil as a
- wax
- solid fat
- non-drying oil - mainly monounsat
- semi-drying oil - mixture
- drying oil - mainly polyunsat
what is the saponification value a measure of
- differentiates true fats (fatty acid esters of glycerol) from waxes (fatty acid esters of monhydric alcohols)
- true fats have high saponification values
hydroxyl value is a measure of
the number of OH groups in the sample
peroxide value is indicative of
- oxidation or rancidity
- a high peroxide value indicates degradation by oxidative processes has occurred
unsaponifiable matter is a measure of
- the extent of non-glyceride matter
- indicative of adulteration
- high value indicates adulteration
commercially processed true fats consist of 99.5% triglycerides, the remaining 0.5% is made up of these 5 things
- sterols (cholesterol)
- unsaturated hydrocarbons
- complex lipids
- pigments
- oil soluble vitamins
decomposition of oils occurs by these 3 primary reactions
- hydrolysis
- methyl ketones
- oxidation
hydrolysis of oils occurs as a result of __3 things__and produces this_____. this can be prevented by
- moisture, bacteria or lipases
- free fatty acids
- undesirable odors or taste
- prevent by keeping moisture below 0.01%
formed when fungi convert free fatty acids or triglycerides to this
methyl ketones
methyl ketones will impac the oil by
how can methyl ketone formation be prevented
- changing flavour or taste making offensive
- not using cork which could be source of fungi, keeping moisture level low, and storing in cool temp
which oil/fat types are most susceptible to oxidative decomposition
- semi-drying and drying oils
- because of the greater degree of unsaturation in the fatty acids makes the molecule more unstable
what is autoxidation
- is spontaneous oxidation which occurs at room temp in the pesence of light and air
hydrogen peroxidases are responsbile for the development of off flavours which on decomposition produce objectionable compounds such as
aldehydes
oxidative changes in simple fats/oils include these two things
- oxidative rancidity
- flavour reversion
oxidative rancidity of fats/oils is caused by
- autoxidation of all unstaturated fatty acids
flavour reversion is the result of autoxidation of this and mainly affects these oils
- unsaturated fatty acids with 3 or more double bonds
- semi-drying or drying oils only
autoxidative decomposition of fats/oils can be prevented by
- storing in air tight container, no light, cool temperature, adding antioxidants
- minimization of air maintained by filling the container full
antioxidants used in preservation of fixed oils/fats fall into 3 categories. which are commonly used with lipids
- reducing agents*
- antioxidant synergists*
- true or primary antioxidants
antioxidant synergists
- chelating agents
- enhance the action of primary or true antioxidants by reactinv with heavy metal ions which catalyze in stage 1 of autoxidation
- e.g. citric acid, lecithin, tartaric acid
what are some challenges with the use of antioxidant synergists (2)
- they need to be added early in the extraction process
- can increase acid values if used at too high a level
true or primary antioxidants inhibit oxidation by
- reacting with free radicals blocking the chain reaction in catalytic autoxidation
- e.g. tocopherol (vitamin E), BHA and BHT (butylated hydroxyanisole/butylated hydroxytoluene)
waxes are materials which are
solid, non-greasy and melt at low temp
e.g. carbowax
these waxes are esters of HMW monohydric alcohols and HMW straight chain fatty acids
true waxes
what are sources of wax and uses
animals and plants
- carnuba wax - leaves of wax palm
- tablet polishing
- beeswax - honeycomb
- ointments
- woolfat - anyhydrous lanolin from sheep wool
- emollient creams
- wool alcohols - alcoholic fraction of wool fat
- ointments
how are waxes obtained
typically mechanical dislodgement followed by solvent extraction
natural waxes are made up of complex mixtures of (3)
- fatty acids and fatty alcohols
- as free or combined esters
- generally < C16
properties of waxes that distinguish them from true fats (5)
- difficult to saponify
- low saponification values
- low idodine values
- higher acid values
- higher unsaponifiable matter
how are waxes standardized (10)
- acid value
- iodine value
- saponification value
- selective solubility
- melting point
- ester value
- ratio number
- sulfated ash
- acid/alkaline substances
- weight of parrafins
