Sodium propylparaben
[CAS# 35285-69-9]

Identification

• Classification: Organic raw materials >> Organometallic salt
• Name: Sodium propylparaben
• Synonyms: Propyl 4-hydroxybenzoate sodium salt; Propyl p-hydroxybenzoate sodium salt; Propylparaben sodium; Sodium propyl p-hydroxybenzoate; 4-Hydroxybenzoic acid propyl ester sodium salt
• Molecular Formula: C₁₀H₁₁NaO₃
• Molecular Weight: 202.18
• CAS Registry Number: 35285-69-9
• EC Number: 252-488-1
• SMILES: CCCOC(=O)C1=CC=C(C=C1)[O-].[Na+]

Properties

• Density: 1.24 g/mL (25 ºC) (Expl.)
• Melting point: 302 ºC (Expl.)

Safety Data

• Hazard Symbols: GHS05 Danger
• Hazard Statements: H318-H412
• Precautionary Statements: P264+P265-P273-P280-P305+P354+P338-P317-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Serious eye damage	Eye Dam.	1	H318
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H312

Discovory and Applicatios

Sodium propylparaben, the sodium salt of propyl p-hydroxybenzoate, is a widely used antimicrobial preservative in pharmaceuticals, cosmetics, and personal care products. It belongs to the class of parabens, a group of esters of p-hydroxybenzoic acid known for their effective broad-spectrum antimicrobial activity. The compound has the molecular formula C₁₀H₁₁NaO₃ and appears as a white to off-white powder that is freely soluble in water, making it particularly suitable for use in aqueous formulations.

The use of parabens as preservatives dates back to the early 20th century when their efficacy against mold and yeast was first recognized. Sodium propylparaben was introduced as a more water-soluble form of propylparaben, which itself is only sparingly soluble in water. By converting the ester to its sodium salt, formulators are able to incorporate it into water-based systems more effectively, particularly in emulsions, suspensions, and solutions where even distribution of the preservative is critical to maintaining product stability and safety.

In the pharmaceutical industry, sodium propylparaben is commonly included in liquid dosage forms such as oral syrups, topical creams, ophthalmic solutions, and injectables. It is used alone or in combination with other preservatives, especially methyl and ethylparabens, to achieve synergistic antimicrobial activity and cover a broader range of microorganisms. The typical concentration used in formulations ranges from 0.01% to 0.2%, depending on the nature of the product and the regulatory limits in place in specific jurisdictions.

The cosmetic and personal care industry also makes extensive use of sodium propylparaben. It is included in a wide range of products such as lotions, shampoos, conditioners, deodorants, and make-up. In these applications, it protects the formulations from microbial contamination during manufacturing and consumer use. Its solubility and chemical stability over a range of pH values, generally between pH 4 and 8, allow for flexible formulation in various product types. Sodium propylparaben helps to extend the shelf life of products and maintain their quality, texture, and safety.

Sodium propylparaben is also used in some food-related applications, although this usage is subject to stricter regulation. When permitted, it may be found in processed foods and beverages to inhibit the growth of spoilage organisms. However, methylparaben and ethylparaben are more commonly employed in food systems due to their smaller alkyl groups and more favorable solubility characteristics.

Toxicological studies have shown that sodium propylparaben, like other parabens, is rapidly absorbed and metabolized in the body. It is hydrolyzed to p-hydroxybenzoic acid, which is conjugated and excreted in the urine. The compound exhibits low acute and chronic toxicity, and numerous evaluations by international regulatory agencies have supported its safety when used within established limits. Regulatory organizations such as the U.S. Food and Drug Administration and the European Commission have allowed the use of sodium propylparaben in pharmaceuticals and cosmetics within specific concentration thresholds.

Although parabens have been scrutinized for their potential estrogenic activity, the weight of scientific evidence indicates that the weak endocrine activity observed in some in vitro studies does not translate into significant health risks at the exposure levels found in regulated products. Therefore, sodium propylparaben continues to be approved for use under current safety assessments and is subject to ongoing review.

Chemically, sodium propylparaben is stable under normal storage conditions and is compatible with a wide range of formulation ingredients, including emulsifiers, surfactants, and solvents. It is generally added to formulations during the aqueous phase processing stage to ensure proper dispersion. Its stability in formulation is supported by its resistance to hydrolysis and oxidation under typical manufacturing and storage conditions.

Sodium propylparaben remains a valuable preservative in modern product development due to its efficacy, solubility, and favorable safety profile. Its broad-spectrum activity and regulatory acceptance make it a reliable component in the preservation of many types of formulations.

References

2014. Antifungal activity of sodium propylparaben alone or in combination with low doses of imazalil against Penicillium decay on citrus fruit. European Journal of Plant Pathology, 140(2).
DOI: 10.1007/s10658-014-0450-5

2018. The Chemical and Products Database, a resource for exposure-relevant data on chemicals in consumer products. Scientific Data, 5, Article number: 180125.
DOI: 10.1038/sdata.2018.125

2006. Combined Inventory of Ingredients Employed in Cosmetic Products (2000) and Revised Inventory (2006).
DOI: 10.5281/zenodo.2624118