Propylparaben

Preparation

Produced by esterfying p-hydroxybenzoic acid with n-propanol, using an acid catalyst such as sulfuric acid and an excess of propanol. The materials are heated in a glass-lined reactor under reflux. The acid is then neutralized with caustic soda and the product is crystallized by cooling. The crystallized product is centrifuged, washed, dried under vacuum, milled and blended, all in corrosion-resistant equipment to avoid metallic contamination.

Pharmaceutical Applications

Propylparaben is widely used as an antimicrobial preservative in cosmetics, food products, and pharmaceutical formulations.
It may be used alone, in combination with other paraben esters, or with other antimicrobial agents. It is one of the most frequently used preservatives in cosmetics.
The parabens are effective over a wide pH range and have a broad spectrum of antimicrobial activity, although they are most effective against yeasts and molds.
Owing to the poor solubility of the parabens, the paraben salts, particularly the sodium salt, are frequently used in formulations. This may cause the pH of poorly buffered formulations to become more alkaline.
Propylparaben (0.02% w/v) together with methylparaben (0.18% w/v) has been used for the preservation of various parenteral pharmaceutical formulations.

The Uses of Propylparaben

Propylparaben is in the paraben family of preservatives used by the food, pharmaceutical, and personal care product industries. Parabens mimic estrogen and can act as potential hormone (endocrine) system disruptors.

storage

Aqueous propylparaben solutions at pH 3–6 can be sterilized by autoclaving, without decomposition.At pH 3–6, aqueous solutions are stable (less than 10% decomposition) for up to about 4 years at room temperature, while solutions at pH 8 or above are subject to rapid hydrolysis (10% or more after about 60 days at room temperature).

Safety

Propylparaben has been used as an antimicrobial preservative in the food, cosmetic, and pharmaceutical industries for over 50 years. The chemical formula for propylparaben is C10H12O3.

Propylparaben is easily absorbed through the gastrointestinal tract and skin, and metabolites are rapidly excreted in the urine. It does not appear to accumulate in the body. It is on the FDA generally regarded as safe list.

Regulatory Status

Propylparaben and methylparaben are affirmed GRAS direct food substances in the USA at levels up to 0.1%. All esters except the benzyl ester are allowed for injection in Japan. In cosmetics, the EU and Brazil allow use of each paraben at 0.4%, but the total of all parabens may not exceed 0.8%. The upper limit in Japan is 1.0%.
Accepted as a food additive in Europe. Included in the FDA Inactive Ingredients Database (IM, IV, and SC injections; inhalations; ophthalmic preparations; oral capsules, solutions, suspensions, and tablets; otic, rectal, topical, and vaginal preparations).
Included in parenteral and nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.