Sorbic acid

• BPSorbic Acid
• Ph. Eur.Sorbic Acid
• USP–NFSorbic Acid

Acidum sorbicum; (E,E)-hexa-2,4-dienoic acid; 2-propenylacrylic acid; 2,4-hexadienoic acid; E200

(2E,4E)-Hexa-2,4-dienoic acid · [110-44-1]

UNII X045WJ989B · PubChem CID 643460

C6H8O2 · 112.13

Antimicrobial preservative

Typical concentrations: 0.05–0.2% · Dosage forms: Liquid, Semi-solid

Sorbic acid is an antimicrobial preservative, with antibacterial and particularly antifungal activity, used in oral and topical pharmaceuticals and in cosmetics and foods, at concentrations of about 0.05–0.2%. Its activity depends on the undissociated acid, so it is effective up to about pH 6 and best below pH 5. It is often combined with other preservatives or glycols, which have a synergistic effect.

A free-flowing, white crystalline powder with a faint characteristic odour.

pKa

4.76 at 25 °C

Melting point

132–135 °C

Boiling point

about 228 °C, with decomposition

Solubility

slightly soluble in water; freely soluble in ethanol; soluble in propylene glycol and in fixed oils to a limited extent

Sensitive to oxidation, especially in aqueous solution and in the presence of light; oxidation causes discoloration and loss of activity, and is accelerated by heat and by some metal ions. Antioxidants and protection from light improve stability. Store the solid in a well-closed container, protected from light, at a temperature not exceeding about 40 °C.

Incompatible with bases, oxidising agents and reducing agents. Some loss of antimicrobial activity occurs with nonionic surfactants and through sorption into plastics,.

Produced commercially by condensation of crotonaldehyde with ketene to give a polyester, which is then hydrolysed to sorbic acid. It occurs naturally in rowan (mountain ash) berries.

Sorbic acid is metabolised like other fatty acids and has low systemic toxicity. It may cause skin irritation and, occasionally, allergic or non-immunological contact urticaria and dermatitis when applied topically. JECFA has set a group ADI of 0–25 mg/kg body-weight for sorbic acid and its salts.

Observe normal precautions for the quantity handled. The dust is irritant to the eyes, skin and respiratory tract; wear eye protection, gloves and a dust mask.

GRAS listed. Accepted as a food additive in Europe (E200). Included in the FDA Inactive Ingredient Database (oral capsules, solutions, syrups and tablets; topical and vaginal preparations) and in non-parenteral medicines licensed in Europe.

Potassium sorbate; calcium sorbate; benzoic acid; sodium benzoate.

Because sorbic acid dissolves slowly and poorly in water, the more soluble potassium sorbate is often used and the pH then adjusted to form the active acid in situ. Check preservative content during stability studies, since oxidative loss can be significant.