Efficacy
Anecdotal claims for an antimicrobial effect are based on a few abstract scientific experiments which show some antimicrobial activity for commercial grapefruit seed extracts and an ethanol grapefruit seed extract but not a natural GSE.
[17][18][19] The preliminary studies for the antimicrobial effect state that the Citricidal commercial brand of GSE was used for testing.
[17][18] There is considerable scientific evidence that the anti-microbial activity associated with grapefruit seed extract is attributable to the contamination or adulteration of commercial GSE preparations with synthetic antimicrobials or preservatives.
[2] According to the 2001 GSE study, branded commercial GSE preparations were contaminated with synthetic
benzethonium chloride that was implausible to be made from grapefruit seeds.
[5] Some of the marketers claimed that their product does not contain benzethonium chloride and the error was due to the similarity in molecular weight of the quaternary ammonium compound which was formed through a proprietary manufacturing process.
[5] It is inconceivable that the preservative benzethonium chloride is formed during any extraction and/or processing of grapefruit seeds and pulp.
[5] Researchers conclusively demonstrated the presence of benzethonium chloride in commercial GSE using various analytical methods including HPLC, one- and two-dimensional NMR, PIXE analysis, and electrospray ionization MS.
[5] Another in vitro study claimed GSE had antibacterial properties.
[19] As with the branded in vitro test
[17][18] this extract was contaminated.
[5] The ethanolic grapefruit seed and pulp extract tested was prepared or contaminated with ethanol, a chemical solvent used in the extraction process.
[19] Ethanol, also known as ethyl alcohol, is effective in inhibiting bacteria.
[20]
Independent studies have shown that commercial preparations contain the compound
benzalkonium chloride, which is a synthetic antimicrobial commonly used in disinfectants and cleaning products, the related compound
benzethonium chloride, the antibiotic
triclosan, or the preservative
methylparaben.
[1][6][21] Some samples were shown to contain up to 22% benzalkonium chloride by weight, despite the known
allergenicity[22] and
toxicity[23] of the compound at higher doses.
[6] These chemicals were not present in grapefruit seed extracts prepared in the
laboratory, and GSE preparations without the contaminants were found to possess no detectable antimicrobial effect.
[1] Although citrus seed extract is sold in health food markets,
[6] there is no good evidence for any natural antimicrobial activity.
[1][7]
A study that examined the antiviral properties of GSE found that GSE had no efficacy as a disinfectant for
feline calicivirus and
feline parvovirus.
[24] Grapefruit seed extract has been advocated to be a powerful
antimicrobial with proven activity against
bacteria and
fungi. However, independent studies have shown the efficacy of grapefruit seed extract as an antimicrobial is not demonstrated. Although citrus seed extract is claimed to be a highly effective plant-based preservative by some
natural personal care manufacturers, studies asserted that the universal antimicrobial benefits associated with GSE are merely from the presence of synthetic
preservatives.
Natural GSE has no antimicrobial properties.
[1][2] Newer studies found many commercial grapefruit seed extracts contaminated with synthetic preservatives.
[8][9][10] In a 2007 study the main synthetic antimicrobial agent identified in commercial GSE samples was benzethonium chloride.
[8] In a 2008 study synthetic disinfectants such as benzethonium or benzalkonium chloride were identified in most of the commercial GSE products.
[9] In a 2008 study suspected counterfeit products were determined to contain benzethonium chloride in grapefruit seed extract samples.
[10]
Annoying.
