Grapefruit Seed Extract
Grapefruit Seed Extract is commonly reported to have powerful antimicrobial activity. Some manufacturers claim that it is highly effective in a variety of microbial infections, including these organisms:
- Fungi
- Aspargillosis
- Candida albicans
- Trichophyton sp (ringworm)
- Bacteria
- Klebsiella
- Pseudomonas
- Escherichia coli (E. coli)
- Clostridium
- Salmonella
Companies that manufacture grapefruit seed extract products claim to have extensive research proving their beneficial effects. Some companies even publish extensive "scientific" evaluations of their products' effectiveness on their web pages.
However, when carefully analyzed and studied, grapefruit seed extract products appear to have little or no antimicrobial properties. Even more curious is the fact that almost all of the grapefruit seed extract products on the market contain preservatives that are intended to prevent the growth of bacteria and fungi! This would make one wonder why, if these extracts were so powerful, the full strength concentrate (which should be far more effective in preventing microbial growth than the label recommended diluted dose) needs any preservative at all?
Also, when WellVet.com evaluated the claims of one of the companies, the parts per million (ppm) dose needed to control the various organisms in the sensitivity study were actually remarkably high. In reality, it would be impossible to achieve blood levels approaching those needed for the product to work. For example, to achieve control of Pseudomonas, 20,000 PPM was needed to achieve effective control. It is quite impossible to reach such concentrations in the bird's body, let alone consider what toxic damage might occur due to the presence of the preservatives in the product.
It seems to us at WellVet.com that the entire effectiveness of grapefruit seed extract is due totally to the presence of the preservatives, and the grapefruit seed extracts have no antimicrobial effects on their own.
For those who would like to look further into this issue, we offer the following abstracts of scientific studies involving grapefruit seed extracts:
These abstracts are from PubMed.
Von Woedtke T, Schluter B, Pflegel P, Lindequist
U, Julich WD. Institute of Pharmacy, Ernst Moritz Arndt University,
Greifswald, Germany. Aspects of the antimicrobial efficacy of grapefruit
seed extract and its relation to preservative substances contained.
Pharmazie 1999, Jun:54(6):452-6
The antimicrobial efficacy as well as the content of preservative
agents of six commercially available grapefruit seed extracts were
examined. Five of the six extracts showed a high growth inhibiting
activity against the test germs Bacillus subtilis SBUG 14, Micrococcus
flavus SBUG 16, Staphylococcus aureus SBUG 11, Serratia marcescens
SBUG 9, Escherichia coli SBUG 17, Proteus mirabilis SBUG 47, and Candida
maltosa SBUG 700. In all of the antimicrobial active grapefruit seed
extracts, the preservative benzethonium chloride was detected by thin
layer chromatography. Additionally, three extracts contained the preserving
substances triclosan and methyl parabene. In only one of the grapefruit
seed extracts tested no preservative agent was found. However, with
this extract, as well as with several self-made extracts from seed
and juiceless pulp of grapefruits (Citrus paradisi), no antimicrobial
activity could be detected (standard serial broth dilution assay,
agar diffusion test). Thus, it is concluded that the potent as well
as nearly universal antimicrobial activity being attributed to grapefruit
seed extract is merely due to the synthetic preservative agents contained
within. Natural products with antimicrobial activity do not appear
to be present.
Xiong H, Li Y, Slavik MF, Walker JT. Spraying chicken skin with selected
chemicals to reduce attached Salmonella typhimurium.
Department of Biological & Agricultural Engineering, University
of Arkansas, Fayetteville 72701, USA. J Food Prot 1998 Mar;61(3):272-5
Aqueous solutions of 5% and 10% trisodium phosphate (TSP), 0.1% and
0.5% cetylpyridinium chloride (CPC), 1% and 2% lactic acid (LA), and
0.1% and 0.5% grapefruit seed extract (DF-100) were evaluated in prechill
spraying for reducing Salmonella typhimurium attached on chicken skins.
Chicken skins were inoculated with S. typhimurium and then sprayed
with the selected chemical solutions for 30 sec at 206 kPa and 20
degrees C. After chemical spraying, the skins were rinsed by spraying
tap water for 30 sec. Each skin was stomached in buffered peptone
water (BPW) for 1 min. The stomaching water was then diluted serially,
inoculated onto both xylose lysine tergitol (XLT4) agar and Aerobic
Plate Count (APC) Petrifilm, and incubated for 24 hr at 37 degrees
C. The results showed that the numbers of Salmonella on the chicken
skins after the chemical spraying were significantly lower than those
without spray (P < 0.05). The CPC reduced Salmonella by 1.5 to
1.9 log10. TSP resulted in a 2.1 to 2.2 log10 reduction of Salmonella
and DF-100 produced a 1.6 to 1.8 log10 reduction of Salmonella. The
LA had a number of Salmonella with a 2.2 log10 reduction. The 0.5%
CPC resulted a significantly greater reduction in Salmonella than
0.1% CPC. There were no significant differences in Salmonella reduction
between different concentrations of the other three chemicals.
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Sakamoto S, Sato K, Maitani T, Yamada T. [Analysis
of components in natural food additive "grapefruit seed extract"
by HPLC and LC/MS] [Article in Japanese] Eisei Shikenjo Hokoku 1996;(114):38-42
The components in a commercial natural food additive, "Grapefruit
seed extract", and the ethanol extract of grapefruit seeds were
analyzed by HPLC and LC/MS. The HPLC chromatogram of the commercial
grapefruit seed extract was quite different from that of the ethanol
extract of grapefruit seeds. Three main peaks were observed in the
chromatogram of the commercial grapefruit seed extract. By comparison
of the retention times and the absorption spectra with those of authentic
samples, two peaks were ascribed to methyl-p-hydroxybenzoate and 2,4,4'-trichloro-2'-hydroxydiphenylether
(triclosan). Triclosan was also identified by LC/MS by using the negative
electrospray ionization method.
Calori-Domingues MA, Fonseca H. Laboratory
evaluation of chemical control of aflatoxin production in unshelled
peanuts (Arachis hypogaea L.).
Departamento
de Ciencia e Tecnologia Agroindustrial, Escola Superior de Agricultura,
Universidade de Sao Paulo, Piracicaba, Brazil. Food Addit Contam 1995
May-Jun;12(3):347-50
Propionic acid (ammonium salt) at 3000 mg/kg (PA1) and 5000 mg/kg
(PA2) of unshelled peanuts (UP); grapefruit seed extract at 5000 mg/kg
(GF1) and 10,000 mg/kg (GF2); sodium orthophenylphenate at 2500 mg/kg
(SOP1) and 5000 mg/kg (SOP2); thiabendazole 1000 mg/kg (TBZ1) and
5000 mg/kg (TBZ2) were studied in the laboratory, to verify their
efficiency in controlling fungal growth and aflatoxin (AF) production
on moist UP (16-18% moisture content). Moist UP were put into polyethylene
bags with cotton plugs and incubated at 30 +/- 2 degrees C for 28
days. Treatments were considered efficient when the AF content (B1
+ G1) remained under 30 micrograms/kg. PA1 treatment was efficient
until 14 days of incubation and PA2 during the whole incubation period
(28 days). All other treatments were not efficient, showing AF contents
from 150 to 108,333 micrograms/kg during the incubation periods. Propionic
acid, used as ammonium propionate, at 5000 mg/kg shows promise in
controlling aflatoxin production when applied to moist unshelled peanuts.
Ranzani MR, Fonseca H. Mycological evaluation of chemically-treated
unshelled peanuts. Departamento de Ciencia e Tecnologia Agroindustrial,
Universidade de Sao Paulo, Piracicaba, Brazil. Food Addit Contam 1995
May-Jun;12(3):343-6
In the present work, the effect of propionic acid (ammonium salt) at
3000 mg/kg of unshelled peanuts (PA1) and at 5000 mg/kg (PA2), grapefruit
seed extract at 5000 mg/kg (GF1) and 10,000 mg/kg (GF2), sodium orthophenylphenate
at 2500 mg/kg (SOP1) and at 5000 mg/kg (SOP2) and thiabendazole at 1000
mg/kg (TBZ1) and at 5000 mg/kg (TBZ2) was studied for controlling total
and potentially aflatoxigenic fungi in unshelled peanuts (UP). Samples
of sound mature UP were moistened by adding water and kept refrigerated
till they reached 16% moisture. The samples were then sprayed with the
chemical solutions and incubated at 30 +/- 2 degrees C for 28 days.
Control samples were sprayed with water. An evaluation of total and
aflatoxigenic fungi was made, in pods of UP and in kernels obtained
aseptically, before and at 7, 14, 21 and 28 days of incubation, by serial
dilution in culture media Dichloran Rose Bengal Chloramphenicol (total
fungi count) and in Aspergillus flavus parasiticus Agar (potentially
aflatoxigenic count). In relation to the period and conditions of this
experiment the overall best treatment was PA2, when the lowest average
value of total and aflatoxigenic fungi were obtained in UP and were
maintained in its kernels. Although SOP2 treatment could control fungal
contamination in pods, it was not effective in controlling contamination
through the kernels. The other treatments were ineffective.