Propylparaben (Propyl hydroxybenzoate) CAS 94-13-3

Propylparaben (Propyl hydroxybenzoate) – Broad-Spectrum Preservative for Pharmaceuticals, Cosmetics, and Food

Basic Information

• CAS Number: 94-13-3

• Molecular Formula: C₁₀H₁₂O₃

• Molecular Weight: 180.20 g/mol

• Synonyms: Propyl 4-hydroxybenzoate, Propyl parahydroxybenzoate, E216

• Appearance: White crystalline powder

• Melting Point: 95–98°C

• Solubility: Slightly soluble in water; freely soluble in ethanol, propylene glycol, and other organic solvents

• Storage: Store in a cool, dry place, protected from light and moisture

Overview
Propylparaben (propyl hydroxybenzoate) is a widely used preservative belonging to the paraben family. It is the propyl ester of p‑hydroxybenzoic acid and is valued for its broad‑spectrum antimicrobial activity against bacteria, yeasts, and molds. It is commonly employed in pharmaceuticals, cosmetics, and food products to extend shelf life and prevent microbial contamination. At approved concentrations, propylparaben is considered safe and effective.

Mechanism of Action
Propylparaben inhibits microbial growth by disrupting cell membrane integrity and interfering with enzyme systems essential for microbial metabolism. Its effectiveness is enhanced at acidic to neutral pH (optimal range 4–8) and is often combined with other parabens (e.g., methylparaben) for synergistic protection against a wider range of microorganisms.

Applications

• Pharmaceuticals: Used as a preservative in topical creams, ointments, ophthalmic solutions, syrups, and injectable formulations.

• Cosmetics and personal care: Incorporated into lotions, creams, shampoos, makeup, sunscreens, and wet wipes to prevent microbial contamination.

• Food industry: Used as a preservative (E216) in sauces, dressings, baked goods, beverages, and other processed foods (subject to regional regulations).

• Other: Occasionally used in industrial products such as adhesives and paints.

Pharmacokinetics and Metabolism
Upon absorption, propylparaben is rapidly hydrolyzed to p‑hydroxybenzoic acid, which is conjugated and excreted primarily in urine. Its metabolism and elimination are well‑characterized, making it one of the most studied preservatives in terms of safety profile.

Key Benefits

• Effective at low concentrations (typically 0.01–0.3%).

• Broad‑spectrum activity – controls bacteria, yeasts, and molds.

• Good compatibility with most formulation ingredients.

• Stable over a wide pH range (4–8).

• Cost‑effective and well‑established in regulatory frameworks.

Handling and Storage

• Store in a cool, dry place, protected from light and moisture.

• Keep containers tightly sealed to prevent contamination.

• Use appropriate personal protective equipment (gloves, safety goggles, dust mask) when handling.

• Avoid inhalation of dust and contact with skin and eyes.

Quality Assurance
Each batch is tested for purity (by HPLC), melting point, heavy metals, and microbial quality to ensure compliance with pharmaceutical, cosmetic, and food-grade standards.