Isotopic Fingerprinting and NMR
Analysis Detects Designer Blends Made with Animal Fats Marketed as Saw Palmetto
Extracts
Reviewed: Perini M, Paolini M, Camin F, Appendino G, Vitulo F, De
Combarieu E, Sardone N, Martinelli EM, Pace R. Combined use of isotopic
fingerprint and metabolomics analysis for the authentication of saw palmetto (Serenoa repens) extracts. Fitoterapia.
2018;127:15-19.
Keywords: Adulteration, animal fats, GC-FID, 1H NMR,
isotopic fingerprint, metabolomics, Serenoa repens
Saw palmetto (Serenoa repens, Arecaceae) berry extracts are widely used in
dietary supplement products for urinary problems related to benign prostatatic
hyperplasia. The geographic area where the saw palmetto tree naturally occurs is
limited to the southeastern United States, and due to a limited supply, growing
demand, and increasing prices, the appearance of vegetable oils, or mixtures of
vegetable oils (e.g., canola, coconut, olive, palm, sunflower oils) with saw
palmetto extracts marketed as authentic saw palmetto oil has been observed.1
The problem of saw palmetto adulteration is exacerbated in years when the
harvest volume is low due to inclement weather conditions.
Over the past years,
suppliers have noticed the sale of saw palmetto extracts that appeared to
comply with the pharmacopeial fatty acid ratio requirements,2,3 one
of the main tests to detect saw palmetto extract adulteration. However, these
ingredients sometimes failed other tests, such as color specifications, or
limits on fatty alcohol and sterols.
The approach taken by the
researchers from Indena, SpA (Milan, Italy), the Fondazione Edmund Mach (San
Michele all’Adige, Italy), and the University of Eastern Piedmont (Novara,
Italy), was to evaluate nine commercial extracts (from suppliers outside Europe
and North America) and 30 authentic saw palmetto extracts by the fatty acid
method of the United States Pharmacopeia (USP),2 and by orthogonal
methods, such as 1H NMR and isotopic fingerprinting analysis with a subsequent
statistical assessment by principal component analysis (PCA).
For the isotopic fingerprint
analysis, the 14C concentration, and the ratios of 87Sr/86Sr,
13C/12C, 18O/16O, and 2H/1H
were determined. The amount of 14C in a sample is indicative of its
being derived from plants or from fossil-fuel (i.e., made by chemical
synthesis). The strontium (87Sr/86Sr) ratio provides
information about the nature of the soil and the climatic conditions from where
the sample is obtained. The carbon (13C/12C) ratio can be
used to distinguish among certain plant-derived materials, since not all plants
use the same photosynthetic pathways. As such, materials derived from corn or
sugar cane have higher 13C/12C ratios than most of the
plants used medicinally. The oxygen (18O/16O) and
hydrogen (2H/1H) ratios are based on the local water
composition, mainly influenced by precipitation in form of snow and rain in the
area.
No differences were observed
in the 14C concentrations, and the 87Sr/86Sr
ratio among authentic saw palmetto extracts and the commercial samples.
However, the 13C/12C ratio was slightly, but
significantly lower in the commercial samples, suggesting adulteration. This
was confirmed by the 18O/16O, and 2H/1H
ratios, which differed substantially from those of the authentic material.
Comparison with 18O/16O, and 2H/1H
ratios from various fats and oils suggested that six out of the nine commercial
samples were derived from animal fats.
The GC-FID analysis of the fatty acids with subsequent
PCA led to a clustering of the six animal-derived ingredients with the
authentic saw palmetto, suggesting that these ingredients were blended with the
fatty acid composition of authentic saw palmetto in mind. Two of the three
remaining commercial saw palmetto extracts clustered with coconut (Cocos nucifera, Arecaceae) and babaçu (Attalea speciosa, Arecaceae) oil, while one sample
neither clustered with authentic saw palmetto extract nor with any of the
vegetable oils.
A clear separation between
adulterated and genuine saw palmetto extracts based on differences in the 1H
NMR metabolomics was also obtained for seven of the ten samples analyzed
(apparently one additional commercial sample was evaluated by 1H
NMR). The remaining three commercial samples clustered closely to the authentic
materials. It is not clear if the 1H NMR approach would have been
sufficient to detect the adulteration in these three cases, although a
refinement of the statistical model may have provided more clarity on this.
Comment: This paper provides the first evidence for the use of
animal fats to adulterate saw palmetto extracts. It also shows the
sophistication with which fraudulent suppliers are able to create extracts that
are so similar in the composition to the authentic extracts that the
adulteration most likely will go unnoticed when using standard analytical
methods. For some of these materials, differences in color and smell (as saw
palmetto smells very foul) may provide the first indication of a quality issue.
For other commercial extracts, only additional tests, such as the isotopic
fingerprinting described here, may provide sufficient evidence of adulteration.
In order to ensure authentic saw palmetto extract, a tight control of the
supply chain, including assurance that the berries were grown in the United
States and processed by a reputable company, are necessary in addition to a
sound quality control regimen. Extra caution needs to be taken when considering
the purchase of saw palmetto extracts from countries in Asia.
References
- Gafner
S, Baggett S. Adulteration of Saw
Palmetto (Serenoa repens) – Botanical Adulterants Bulletin. Austin, TX: ABC-AHP-NCNPR
Botanical Adulterants Prevention Program. 2017;1-6. http://cms.herbalgram.org/BAP/BAB/SawPalmettoBulletin.html. Accessed June 25, 2018.
- United
States Pharmacopeial Convention. Saw Palmetto Extract. In: United
States Pharmacopeia and National Formulary (USP 41-NF 36). Rockville, MD:
United States Pharmacopeial Convention. 2018.
- The European Directorate for
the Quality of Medicines & HealthCare. European Pharmacopoeia (EP
9.1). Sabalis serrulatae extractum. Strasbourg, France: Council of Europe;
2016:1509-1512.