Benzoin
»Benzoin is the balsamic resin obtained from Styrax benzoinDryander or Styrax paralleloneurusPerkins,known in commerce as Sumatra Benzoin,or from Styrax tonkinensis(Pièrre)Craib ex Hartwich,or other species of the Section Anthostyraxof the genus Styrax,known in commerce as Siam Benzoin (Fam.Styraceae).
Sumatra Benzoin yields not less than 75.0percent of alcohol-soluble extractive,and Siam Benzoin yields not less than 90.0percent of alcohol-soluble extractive.
Packaging and storage—
Preserve in well-closed containers.
Labeling—
Label it to indicate whether it is Sumatra Benzoin or Siam Benzoin.
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 and becoming gritty on chewing.
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 and becoming plastic on chewing.
Identification—
A:
Asolution in alcohol becomes milky upon the addition of water,and the mixture is acid to litmus paper.
B:
Heat a few fragments in a test tube: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.
C:
Heat about 500mg in a test tube with 10mLof potassium permanganate TS:only the Sumatra variety develops a faint odor of benzaldehyde.
Acid-insoluble ash á561ñ:
not more than 1.0%in Sumatra Benzoin;not more than 0.5%in Siam Benzoin.
Foreign organic matter á561ñ:
not more than 1.0%in Siam Benzoin.
Content of benzoic acid—
Treat about 1g of powdered Benzoin with 15mLof warm carbon disulfide,filter through a small pledget of cotton,wash the cotton with an additional 5mLof carbon disulfide,and allow the filtrate to evaporate spontaneously:the weight of the residue is not less than 6.0%(Sumatra Benzoin),or not less than 12.0%(Siam Benzoin)of the weight of Benzoin taken.This residue responds to the tests for Benzoate á191ñ.
Assay—
Place about 2g of Benzoin,accurately weighed,in a tared extraction thimble,and insert the thimble in a continuous-extraction apparatus.Place about 100mg of sodium hydroxide in the receiving flask of the apparatus,and extract the Benzoin with alcohol for 5hours,or until completely extracted.Dry the extraction thimble containing the insoluble residue at 105
for 2hours.On a separate portion of Benzoin,determine the water content as directed for Method IIunder Water Determination á921ñ.Calculate the weight of water in the quantity of the Benzoin taken for 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.
for 2hours.On a separate portion of Benzoin,determine the water content as directed for Method IIunder Water Determination á921ñ.Calculate the weight of water in the quantity of the Benzoin taken for 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.
Auxiliary Information—
Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(PA6)Pharmaceutical Analysis 6
USP28–NF23Page 234
Phone Number:1-301-816-8389