U.S. PHARMACOPEIA

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Milk Thistle Capsules
» Milk Thistle Capsules are prepared from Powdered Milk Thistle Extract. They contain not less than 90.0 percent and not more than 110.0 percent of the labeled amount of silymarin as silybin (C25H22O10), calculated as the sum of silydianin, silychristin, silybin A, silybin B, isosilybin A, and isosilybin B.
Packaging and storage— Preserve in tight, light-resistant containers.
Labeling— The label states the Latin binomial and, following the official name, the article from which the Capsules were prepared. The label also indicates the content of silymarin, in mg per Capsule.
Identification—
A: Thin-Layer Chromatographic Identification Test 201—
Standard solution, Developing solvent system, and Procedure— Proceed as directed for the Identification test under Milk Thistle.
Test solution— Weigh and finely powder the contents of not fewer than 20 Capsules. Transfer a portion of the powder, equivalent to about 50 mg of silymarin, to a suitable container, add 10 mL of methanol, shake for 1 minute, and sonicate for 10 minutes. 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 cfu per g, the total combined molds and yeasts count does not exceed 103 cfu per g, and the enterobacterial count does not exceed 102 per g. It meets the requirements of the tests for absence of Salmonella species and Escherichia coli.
Disintegration and dissolution 2040: meet the requirements for Dissolution.
pH 7.5 Phosphate buffer— Dissolve 27.6 g of monobasic sodium phosphate and 6.08 g of sodium hydroxide in water, and dilute with water to 4000 mL.
Medium: pH 7.5 Phosphate buffer containing 2% lauryl sulfate; 900 mL.
Apparatus 2: 100 rpm.
Time: 45 minutes.
Determine the amount of silymarin as silybin (C25 H20O10) dissolved by employing the method in the test for Content of silymarin, making any necessary modifications.
Tolerances— Not less than 75% of the labeled amount of silymarin as silybin (C25H22O10) is dissolved in 45 minutes.
Weight variation 2091: meet the requirements.
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— Weigh and finely powder the contents of not fewer than 20 Capsules. Transfer an accurately weighed amount of the powder, equivalent to about 100 mg of silymarin, to a 100-mL volumetric flask, add 90 mL of methanol, and sonicate for 20 minutes with occasional shaking. Cool to 20, and dilute with methanol to volume. Filter through a membrane having a 0.45-µm or finer porosity.
Procedure— Proceed as directed in the test for Content of silymarin under Milk Thistle, except to separately calculate the amount, in mg, of each relevant component of silymarin as silybin (C25H22O10) in the portion of Capsules taken by the formula:
100C,
in which the term, C, is as defined therein. Calculate the content of silymarin, in mg, in the portion of Capsules taken by adding the individual amounts.
Residual solvents 467: meet the requirements.
(Official January 1, 2007)
Auxiliary Information— Staff Liaison : Maged H. Sharaf, Ph.D., Senior Scientist
Expert Committee : (DSB05) Dietary Supplements - Botanicals
USP29–NF24 Page 2364
Pharmacopeial Forum : Volume No. 29(2) Page 479
Phone Number : 1-301-816-8318