Saw Palmetto Dietary Supplement Standard Reference Materials

Two Standard Reference Materials containing saw palmetto, SRM 3250 Serenoa repens (Fruit) and SRM 3251 Serenoa repens Extract, have been developed as part of the Analytical Chemistry Division’s program to produce SRMs related to botanical dietary supplements. Both materials have assigned values for their phytosterol and fatty acid content, while SRM 3251 also has assigned values for γ-tocopherol and total β-carotene. The assigned values were determined by using two independent techniques at NIST, while the phytosterols in SRM 3251 also incorporated results from collaborating laboratories. These SRMs are intended primarily for use as measurement controls and for use in the development and validation of analytical methods for saw palmetto.  

The development of dietary supplement SRMs containing saw palmetto was part of a collaborative effort between NIST and the National Institutes of Health, Office of Dietary Supplements (NIH-ODS). Saw palmetto is a dietary supplement material that is used to treat symptoms of benign prostatic hyperplasia, the medical term for an enlarged prostate gland. As with many dietary supplements, consumers believe that botanical dietary supplements will improve their health and that these “natural” remedies are both effective and free from the side effects that may occur with other medications. However, there are occasional reports of inaccurate labeling, adulteration, contamination (with pesticides, heavy metals, or toxic botanicals), and drug interactions. To address these issues, reference materials are needed to support Good Manufacturing Practices (GMPs) for many dietary supplements including saw palmetto.

As with other complex-matrix reference materials produced by NIST, value assignment of the saw palmetto SRMs was performed using multiple independent analytical methods with measurements performed by NIST and collaborating laboratories. Determination of phytosterols in both SRMs necessitated the development of a new liquid chromatographic (LC) method with mass spectrometric (MS) detection. Various column technologies and multiple sample preparation and extraction techniques were investigated for method development. Results obtained with the new LC method were combined with those from a more traditional gas chromatographic (GC) method at NIST and at collaborating laboratories. Fatty acids were determined using two GC methods with different columns and detection modes, and results for γ-tocopherol and total β-carotene were obtained with multiple LC methods. For all analytes, data from the different methods and sources were evaluated statistically and combined to yield the assigned values and expanded uncertainty intervals that are reported in the Certificates of Analysis. SRM 3250, the saw palmetto fruit material, was also screened for toxic elements using inductively coupled plasma (ICP)-MS. 

Major Accomplishments:

• Two natural-matrix SRMs have been produced for saw palmetto:
• • SRM 3250 Serenoa repens (Fruit)
  • SRM 3251 Serenoa repens Extract     
    [click on SRM name to be transferred to a page where you can see the Certificate of Analysis for this material]
• Analytical method has been developed for the measurement of phytosterols using LC-MS.