Chemical Properties
white to light beige crystalline powder
Uses
Propyl Gallate is a known inhibitor of Tyrosinase, a polyphenol oxidase, which is an important enzyme in pigment biosynthesis in various organisms. It has also recently been seen to boost biodiesel li
pid biosynthesis in cultures.
Uses
Antioxidant for cosmetics, foods, fats, oils, ethers, emulsions, waxes, transformer oils.
General Description
Fine white to creamy-white crystalline powder. Odorless or with a faint odor. Melting point 150°C. Insoluble in water. Slightly bitter taste.
Reactivity Profile
PROPYL GALLATE(121-79-9) can react with oxidizing agents. Incompatible with strong acids, strong bases and strong reducing agents. Darkens in the presence of iron and iron salts. Contact with metals should be avoided .
Air & Water Reactions
Insoluble in water.
Hazard
Use in foods restricted to 0.02% of fat con-
tent.
Fire Hazard
This chemical is combustible.
Definition
ChEBI: N-propyl gallate is a trihydroxybenzoic acid.
Preparation
Produced commercially by the esterification of gallic acid with propyl alcohol followed by distillation to remove the
excess alcohol.
Production Methods
Propyl gallate is prepared by the esterification of 3,4,5-trihydroxybenzoic
acid (gallic acid) with n-propanol. Other alkyl gallates are
prepared similarly using an appropriate alcohol of the desired alkyl
chain length.
Flammability and Explosibility
Notclassified
Pharmaceutical Applications
Propyl gallate has become widely used as an antioxidant in
cosmetics, perfumes, foods, and pharmaceuticals since its use in
preventing autoxidation of oils was first described in 1943.It is
primarily used, in concentrations up to 0.1% w/v, to prevent the
rancidity of oils and fats;it may also be used at concentrations of
0.002% w/v to prevent peroxide formation in ether, and at 0.01%
w/v to prevent the oxidation of paraldehyde. Synergistic effects with
other antioxidants such as butylated hydroxyanisole and butylated hydroxytoluene have been reported. Propyl gallate is also said to
possess some antimicrobial properties;
Studies have shown that, when added to powder blends
containing ketorolac, propyl gallate significantly increases the
drug stability in the preparation.
Other alkyl gallates are also used as antioxidants and have
approximately equivalent antioxidant properties when used in
equimolar concentration; however, solubilities vary;
Propyl gallate has also been investigated for its therapeutic
properties, mainly in animal studies.
Biochem/physiol Actions
An antioxidant that exhibits antimicrobial activity. Propyl gallate has been reported to be an effective antioxidant-based hepatoprotector, both in vitro and in vivo. It has also been shown to prevent neuronal apoptosis and block the death of neurons exposed to FeSO4/GA as well as partially protect endothelial cells against TNF-induced apoptosis.
Toxicology
Propyl gallate (n-propyl-3,4,5-trihydroxybenzoate) is used in vegetable oils and butter. When 1.2 or 2.3% propyl gallate was added to feed for rats, loss of weight was observed. This may be due to the rats reluctance to eat food that was contaminated with the bitter taste of propyl gallate. When it was given for 10 to 16 months at the 2 to 3% level, 40% of the rats died within the first month and the remainder showed severe growth inhibition. Autopsies of rats indicated kidney damage resulting from the ingestion of propyl gallate. However, no other animal studies show serious problems and further studies indicated that propyl gallate does not cause serious chronic toxicities.
Safety
It has been reported, following animal studies, that propyl gallate
has a strong contact sensitization potential.Propyl gallate has
also produced cytogenic effects in CHO-K1 cells.However,
despite this, there have been few reports of adverse reactions to
propyl gallate.Those that have been described include contact
dermatitis, allergic contact dermatitis,and methemoglobinemia
in neonates.
The WHO has set an estimated acceptable daily intake for
propyl gallate at up to 1.4 mg/kg body-weight.
(cat, oral): 0.4 g/kg
(mouse, oral): 1.7 g/kg
(rat, oral): 2.1 g/kg
(rat, IP): 0.38 g/kg
storage
Propyl gallate is unstable at high temperatures and is rapidly
destroyed in oils that are used for frying purposes.
The bulk material should be stored in a well-closed, nonmetallic
container, protected from light, in a cool, dry place.
Purification Methods
Crystallise the ester from aqueous EtOH or *C6H6 (m 146-146.5o). [Beilstein 10 III 2078, 10 IV 2003.]
Incompatibilities
The alkyl gallates are incompatible with metals, e.g. sodium,
potassium, and iron, forming intensely colored complexes. Complex
formation may be prevented, under some circumstances, by the
addition of a sequestering agent, typically citric acid. Propyl gallate
may also react with oxidizing materials.
Regulatory Status
GRAS listed. Accepted for use as a food additive in Europe.
Included in the FDA Inactive Ingredients Database (IM injections;
oral, and topical preparations). Included in nonparenteral medicines
licensed in the UK. Included in the Canadian List of
Acceptable Non-medicinal Ingredients.
