Benzoin

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Benzoin is the balsamic resin obtained from Styrax benzoin Dryand. or Styrax paralleloneurus Perkins, known in commerce as Sumatra Benzoin, or from Styrax tonkinensis (Pierre) Craib ex Hartwich, or other species of the Section Anthostyrax of the genus Styrax, known in commerce as Siam Benzoin (Fam. Styraceae).

Sumatra Benzoin yields NLT 75.0% of alcohol-soluble extractive, and Siam Benzoin yields NLT 90.0% of alcohol-soluble extractive.

2 IDENTIFICATION

A. A solution in alcohol becomes milky upon the addition of water, and the mixture is acid to litmus paper.

B. Identification of articles of botanical origin 〈563〉

Analysis: Heat a few fragments in a test tube.

Acceptance criteria: Sumatra Benzoin evolves a sublimate consisting of plates and small, rod-like crystals of cinnamic acid and its esters that strongly polarize light. Siam Benzoin evolves a sublimate directly above the melted mass, consisting of numerous long, rod-shaped crystals of benzoic acid that do not strongly polarize light.

3 ASSAY

Procedure

Sample: Place 2 g of Benzoin in a tared extraction thimble, and insert the thimble in a continuous-extraction apparatus. Place 100 mg of sodium hydroxide in the receiving flask of the apparatus, and extract the Benzoin with alcohol for 5 h, or until completely extracted. Dry the extraction thimble containing the insoluble residue at 105° for 2 h.

Analysis: On a separate portion of Benzoin, determine the water content as directed for Water Determination 〈921〉, Method II. Calculate the weight of water in the quantity of the Benzoin taken for the Assay, and subtract it from the original weight of the Benzoin taken. The difference between this result and the weight of the residue in the extraction thimble represents the alcohol-soluble extractive.

Acceptance criteria: The alcohol-soluble extractive is NLT 75.0% for Sumatra Benzoin and NLT 90.0% for Siam Benzoin.

4 OTHER COMPONENTS

Content of Benzoic Acid

Analysis: Treat 1 g of powdered Benzoin with 15 mL of warm carbon disulfide. Filter through a small pledget of cotton, wash the cotton with an additional 5 mL of carbon disulfide, and allow the filtrate to evaporate spontaneously.

Acceptance criteria: The weight of the residue is NLT 6.0% of the weight of Benzoin taken for Sumatra Benzoin and NLT 12.0% for Siam Benzoin. This residue meets the requirements for Identification Tests—General 〈191〉, Benzoate.

5 IMPURITIES

Inorganic Impurities

Articles of Botanical Origin, Acid-Insoluble Ash 〈561〉: NMT 1.0% in Sumatra Benzoin; NMT 0.5% in Siam Benzoin

Organic Impurities

Procedure: Articles of Botanical Origin, Foreign Organic Matter 〈561〉: NMT 1.0% in Siam Benzoin

6 SPECIFIC TESTS

Botanic Characteristics

Sumatra Benzoin: Blocks or lumps of varying size, made up of tears, compacted together, with a reddish brown, reddish gray, or grayish brown resinous mass; the tears are externally yellowish or rusty brown, milky white on fresh fracture; hard and brittle at ordinary temperatures, but softened by heat.

Siam Benzoin: Pebble-like tears of variable size and shape, compressed, yellowish brown to rusty brown externally, milky white on fracture, separate or very slightly agglutinated; hard and brittle at ordinary temperatures, but softened by heat.

7 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.

Labeling: Label it to indicate whether it is Sumatra Benzoin or Siam Benzoin.