Metabolomic Profiling of Saw
Palmetto Extracts Allows Distinguishing among Materials Produced Using
Different Extraction Methods and to Detect Adulteration with Other Vegetable
Oils
Reviewed: Booker A, Suter A, Krnjic A, et al. A
phytochemical comparison of saw palmetto products using gas chromatography and 1H
nuclear magnetic resonance spectroscopy metabolomic profiling. J Pharm
Pharmacol. 2014;66(6):811-822.
This is another example of collaboration between a
dietary supplement manufacturer (Bioforce AG; Roggwil, Switzerland) and an
academic institution (University of London; London, UK). The research team
analyzed 57
commercial samples (soft gel or hard gel capsules, tablets, or tinctures)
obtained from retail outlets or pharmacies from nine countries in Asia, Europe,
and North America. Of these products, 29 contained only saw palmetto (Serenoa repens syn. Sabal serrulata,
Arecaceae), while the other 28 were labelled as saw palmetto combined with
other constituents such as vitamins, herbal extracts, or minerals. Nine fatty
acids were quantified in 46 products using an established gas
chromatography-flame ionization detector (GC-FID) method. The metabolomic
profiles (metabolomics is the term used for the study of unique chemical
fingerprints produced by cellular processes, such as those seen in plants) of
34 saw palmetto extracts were recorded using 1H NMR spectroscopy,
and analyzed statistically by principal component analysis (PCA).
According
to the results from the GC-FID analysis, the fatty acid composition of the
majority of the saw palmetto mono-preparations was comparable, while products
containing additional ingredients were predictably much more heterogeneous. The
actual contents of fatty acids in the mono-preparations varied between 0.1 and
4.6 times the levels indicated on the label. As expected, products containing
saw palmetto and additional vegetable oils showed a different fatty acid
composition from the 29 mono-preparations.
In
one of the products labeled to contain additional ingredients, 1H
NMR spectroscopy analysis was able to confirm the identity of the added
ingredients as soy (Glycine max,
Fabaceae) bean oil and glycerin. The analysis by 1H NMR spectroscopy
also allowed looking at a wider range of chemical compounds (for example, β-sitosterol,
γ-tocopherol and δ-tocopherols,
or β-carotene) and comparing each of the
products based on their total extractable metabolite content. The metabolic
pattern found in ethanolic preparations showed that the majority of the extract
manufacturers used the same mixture of immature and mature fruits obtained from
a variety of harvesting regions in Florida. The authors conclude that both
methods provide valuable information, and suggest that PCA-based models for saw
palmetto products could be used in product development and quality control, in
particular for the detection of adulterated material.
Comment: Substitution or thinning of saw palmetto
berry extract with other vegetable oils is unfortunately documented as being
relatively common, especially in years where saw palmetto harvests are not
robust enough to meet market demands. A story published in “Natural Products
Insider” in 2009 revealed that palm, canola (Brassica napus,
Brassicaceae), olive (Olea europaea,
Oleaceae), and coconut (Cocos nucifera,
Arecaceae) oils have been found as adulterants, and that the occurrence tends
to escalate after a supply shortage.1 The rather comprehensive
overview on the situation in the marketplace by Booker et al. seems to indicate
a possible improvement of the situation, since all 57 commercial products
actually contained saw palmetto and the presence of additional vegetable oils
was declared on the labels. There are a number of methods (e.g., in the
monographs in the European Pharmacopoeia, the United States Pharmacopeia, or by AOAC International)2-4
to authenticate saw palmetto extracts but detection of adulteration in products
where saw palmetto is mixed with other vegetable oils is still challenging.
Using an analytical fingerprinting technique like GC-FID or 1H NMR
combined with an appropriate statistical analysis is a good way to ensure that
the ingredient has the required composition.
References
1.
Myers S. Saw palmetto quality issues. Natural Products
Insider. September 11, 2009. Available at: http://www.naturalproductsinsider.com/articles/2009/09/saw-palmetto-quality-issues.aspx. Accessed October 29, 2014.
2. European Directorate for the
Quality of Medicines & Healthcare. European Pharmacopoeia (EP 7.4). Strasbourg, France: Council of
Europe; 2011.
3.
United States
Pharmacopeial Convention. Saw palmetto. In: USP
37-NF 32. Rockville, MD: United States
Pharmacopeial Convention; 2014.
4.
Sorenson WR, Sullivan D. Determination of campesterol, stigmasterol, and
beta-sitosterol in saw palmetto raw materials and dietary supplements by gas
chromatography: single-laboratory validation. J
AOAC Int. 2006;89(1):22-34.