U.S. PHARMACOPEIA

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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 90.0 percent and not more than 110.0 percent of the labeled amount of silymarin calculated as silybin (C25H22O10), on the dried basis, consisting of not less than 20.0 percent and not more than 45.0 percent for the sum of silydianin and silychristin, not less than 40.0 percent and not more than 65.0 percent for the sum of silybin A and silybin B, and not less than 10.0 percent and not more than 20.0 percent for the sum of isosilybin A and 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 Labeling under Botanical Extracts 565.
Identification—
A: Thin-Layer Chromatographic Identification Test 201—
Standard solution, Developing solvent system, and Procedure— Proceed as directed for Identification test A under Milk Thistle.
Test solution— Dissolve 100 mg of Powdered Extract in 10 mL of methanol, and allow to stand for 15 minutes before use.
B: The retention times of the peaks for silydianin, silychristin, silybin A, silybin B, isosilybin A, and isosilybin B in the chromatogram of the Test solution correspond to those in the chromatogram of Milk thistle standard solution, as obtained in the test for Content of silymarin.
Microbial enumeration 2021— The total bacterial count does not exceed 104 per g, the total combined molds and yeasts count does not exceed 103 cfu per g, and the enterobacterial count does not exceed 103 cfu per g. It meets the requirements of the tests for absence of Salmonella species, and Escherichia coli.
Loss on drying 731— Dry it at 105 for 2 hours: 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 silymarin under Milk Thistle.
Milk thistle standard solution— Dissolve an accurately weighed quantity of USP Powdered Milk Thistle Extract RS in methanol, sonicate for 20 minutes, and dilute with methanol to obtain a solution having a known concentration of about 0.7 mg of extract per mL.
Test solution— Transfer an accurately weighed amount of Powdered Extract, equivalent to about 40 mg of silymarin, to a 100-mL volumetric flask. Add 70 mL of methanol, and sonicate for 20 minutes. 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 10 µL) of the Milk thistle standard solution, each of the Silybin standard solutions, and the Test solution into the chromatograph, and record the chromatograms. Identify the peaks due to silychristin, silydianin, silybin A, silybin B, isosilybin A, and isolybin B by 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 A and silybin B peaks versus the concentration of USP Silybin RS in 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 C is the concentration, in mg per mL, of the relevant component in the Test solution as interpolated from the calibration graph; and W is 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.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Other requirements— It meets the requirements in the tests for Residual Solvents and Pesticide Residues under Botanical Extracts 565.
Auxiliary Information— Staff Liaison : Maged H. Sharaf, Ph.D., Senior Scientist
Expert Committee : (DSB05) Dietary Supplements - Botanicals
USP29–NF24 Page 2363
Pharmacopeial Forum : Volume No. 28(2) Page 417
Phone Number : 1-301-816-8318