Powdered Milk Thistle Extract
»Powdered Milk Thistle Extract is prepared from Milk Thistle fruits or seeds by fat removal and subsequent extraction with suitable solvents.It contains not less than 90.0percent and not more than 110.0percent of the labeled amount of silymarin calculated as silybin (C25H22O10),on the dried basis,consisting of not less than 20.0percent and not more than 45.0percent for the sum of silydianin and silychristin,not less than 40.0percent and not more than 65.0percent for the sum of silybin Aand silybin B,and not less than 10.0percent and not more than 20.0percent for the sum of isosilybin Aand isosilybin B.
Packaging and storage— Preserve in tight,light-resistant containers,in a cool place.
Labeling— The label states the Latin binomial and,following the official name,the part of the plant from which the article was prepared.It meets the requirements for Labelingunder Botanical Extracts á565ñ.
Identification—
A:Thin-Layer Chromatographic Identification Test á201ñ—
Standard solution,Developing solvent system,and Procedure— Proceed as directed for Identification test Aunder Milk Thistle.
Test solution— Dissolve 100mg of Powdered Extract in 10mLof methanol,and allow to stand for 15minutes before use.
B: The retention times of the peaks for silydianin,silychristin,silybin A,silybin B,isosilybin A,and isosilybin Bin the chromatogram of the Test solutioncorrespond to those in the chromatogram of Milk thistle standard solution,as obtained in the test for Content of silymarin.
Microbial enumeration á2021ñ— The total bacterial count does not exceed 104per g,the total combined molds and yeasts count does not exceed 103cfu per g,and the enterobacterial count does not exceed 103cfu per g.It meets the requirements of the tests for absence of Salmonellaspecies,and Escherichia coli.
Loss on drying á731ñ— Dry it at 105for 2hours:it loses not more than 5.0%of its weight.
Content of silymarin—
Solution A,Solution B,Mobile phase,Silybin standard solutions,and Chromatographic system— Proceed as directed in the test for Content of silymarinunder Milk Thistle.
Milk thistle standard solution— Dissolve an accurately weighed quantity of USP Powdered Milk Thistle Extract RSin methanol,sonicate for 20minutes,and dilute with methanol to obtain a solution having a known concentration of about 0.7mg of extract per mL.
Test solution— Transfer an accurately weighed amount of Powdered Extract,equivalent to about 40mg of silymarin,to a 100-mLvolumetric flask.Add 70mLof methanol,and sonicate for 20minutes.Cool at 20,and dilute with methanol to volume.Pass through a membrane filter having a 0.45-µm or finer porosity.
Procedure— Separately inject equal volumes (about 10µL)of the Milk thistle standard solution,each of the Silybin standard solutions,and the Test solutioninto the chromatograph,and record the chromatograms.Identify the peaks due to silychristin,silydianin,silybin A,silybin B,isosilybin A,and isolybin Bby comparison with the chromatogram of the Milk thistle standard solution,and measure the peak areas of the relevant peaks.Plot the areas of the sum of silybin Aand silybin Bpeaks versus the concentration of USP Silybin RSin the Silybin standard solutions,and obtain a regression line for calibration.Separately calculate the percentage of each relevant component of silymarin as silybin (C25H22O10)in the portion of Powdered Extract taken by the formula:
10,000(C/W),
in which Cis the concentration,in mg per mL,of the relevant component in the Test solutionas interpolated from the calibration graph;and Wis the weight,in mg,of the portion of Powdered Extract taken.Calculate the content of silymarin,in percentage,in the portion of Powdered Extract taken by adding the individual percentages.
Other requirements— It meets the requirements in the tests for Residual Solventsand Pesticide Residuesunder Botanical Extracts á565ñ.
Auxiliary Information— Staff Liaison:Gabriel I.Giancaspro,Ph.D.,Senior Scientist and Latin American Specialist
Expert Committee:(DSB)Dietary Supplements:Botanicals
USP28–NF23Page 2117
Pharmacopeial Forum:Volume No.28(2)Page 417
Phone Number:1-301-816-8343