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UHPLC-UV/MS Method to Authenticate Grapefruit Seed Extracts
Reviewed: Avula B, Sagi S, Wang YH, et al.
Liquid chromatography-electrospray ionization mass spectrometry analysis of
limonoids and flavonoids in seeds of grapefruits, other Citrus species,
and dietary supplements. Planta Med. 2016;82(11-12):1058-1069.
doi: 10.1055/s-0042-107598.
Keywords: Citrus × paradisi, grapefruit
seed extract, benzethonium chloride, synthetic antiseptic, UHPLC-UV/MS
Extracts of grapefruit (Citrus × paradisi,
Rutaceae) seed are a common ingredient in dietary supplements and cosmetic
products, and are promoted as a “natural antibiotic,” but also to improve circulatory
function, the latter based on the presence of flavonoids. According to
manufacturers, in some instances, not only the seed is used for production of
the extract, but also pulp or rind material. However, past analysis of
commercial products has shown that in many cases, synthetic microbicidal
compounds such as benzalkonium chloride, benzethonium chloride, cetrimonium
bromide, or triclosan were labeled and sold as grapefruit seed extract. The
goal of this research project was to establish a fingerprint for authentic
grapefruit seed and a number of seeds from other Citrus
species, and to determine the authenticity of commercial samples labeled to
contain grapefruit seed extract.
Grapefruit seeds, and seeds from bergamot (C. bergamia), lemon (C. × limon), Cleopatra mandarin (C. reshni),
Key lime (C. aurantifolia), citron (C. medica), and pummelo (C. maxima),
were obtained from authenticated trees from the Florida Division of Plant Industry’s
Citrus Arboretum and the United States Department of Agriculture (USDA) Citrus
Arboretum. The 17 commercial samples were purchased in US retail stores (n=2), from
the Internet (n=9), and from pharmacies in Germany (n=2) and Switzerland (n=4).
The samples were analyzed by ultra-high-performance liquid chromatography
coupled to ultraviolet and mass spectrometric detection (UHPLC-UV/MS). Four
commercial samples (24%) were devoid of limonoids, which are
tetranortriterpenoids typically found in seeds of grapefruit. Two of these
samples contained flavonoids typical for Citrus species,
suggesting that these were made with extracts from plant parts other than the
seeds, while the other two were found to contain only benzethonium chloride
(both of which were manufactured by the same company).
Comment: This research project, which was
initiated after Botanical Adulterants Program staff members noticed the lack of
published data on the composition of commercial grapefruit seed extracts other
than the occurrence of synthetic microbicides, provides the basis to
authenticate grapefruit seed material in whole, powdered, or extract form. The
use of a mass spectrometer in positive ion mode allows the easy detection of
quaternary ammonium compounds, such as benzalkonium chloride or benzethonium
chloride. This should provide manufacturers with an appropriate tool to verify
the identity of their raw materials and finished products. Despite the limited
number of samples, the results suggest that occurrence of adulteration has
decreased compared to previous reports,1 and spiking with
synthetic microbicides may be limited to one manufacturer selling benzethonium
chloride labeled as grapefruit seed extract.
Reference
1. Cardellina
JH. The adulteration of commercial “grapefruit seed extract” with
synthetic antimicrobial and disinfectant compounds. HerbalGram.
2012;(94):62-66.
