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.[15][16][17] 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.[18] The preliminary studies for the antimicrobial effect state that the Citricidal brand of GSE was used for testing.[15][16] According to the 2001 GSE study, the Citricidal brand as well as the Nutribiotic brand were both contaminated with synthetic benzethonium chloride that was implausible to be made from grapefruit seeds.[3] Another in vitro study claimed GSE had antibacterial properties.[17] As with the branded in vitro test[15][16] this extract was contaminated.[3] The ethanolic extract tested had become contaminated with ethanol, a chemical used in the extraction process.[17] Ethanol, also known as ethyl alcohol, is effective in inhibiting bacteria.[19] Nevertheless, as a result of marketing by manufacturers in the health food arena and a few misinterpreted studies conducted in vitro that tested contaminated extracts which were not pure GSE processed without solvents or brands which are known to contain preservatives, the controversy over the effectiveness of GSE continues even when studies conclude – self-made pure GSE has no natural antimicrobial properties and commercial GSE has been identified with contamination from synthetic preservatives.[1][3][13][18][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][13][20] Some samples were shown to contain up to 22% benzalkonium chloride by weight, despite the known allergenicity[21] and toxicity[22] of the compound at higher doses.[13] These chemicals were not present in grapefruit seed extracts prepared in the laboratory, and GSE preparations without the contaminants were found to possess no significant antimicrobial effect.[1] Although citrus seed extract is sold in health food markets,[13] there is no good evidence for any natural antimicrobial activity.[1][14]
A study that examined the antiviral properties of GSE found that GSE had no efficacy as a disinfectant for feline calicivirus and feline parvovirus.[23] 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][18] Newer studies found commercial grapefruit seed extracts contaminated with synthetic preservatives such as benzethonium chloride.[4][5][6]
....Some consumers believe this extract is an effective natural preservative even though multiple scientific studies have concluded that the universal antimicrobial activity is merely from contamination with synthetic antimicrobials.[1][3][13][18][20][38]
References
1. von Woedtke T, Schluter B, Pflegel P, Lindequist U, Julich WD. Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained. Pharmazie 1999 54:452–456. Abstract
3. Takeoka G, Dao L, Wong RY, Lundin R, Mahoney N. Identification of benzethonium chloride in commercial grapefruit seed extracts. J Agric Food Chem. 2001 49(7):3316–20. Abstract
4. Avula B, Dentali S, Khan IA, M.A., Simultaneous identification and quantification by liquid chromatography of benzethonium chloride, methyl paraben and triclosan in commercial products labeled as grapefruit seed extract. Pharmazie. 2007 62(8):593–6. Abstract
5. Sugimoto N, Tada A, Kuroyanagi M, Yoneda Y, Yun YS, Kunugi A, Sato K, Yamazaki T, Tanamoto K, Survey of synthetic disinfectants in grapefruit seed extract and its compounded products. Shokuhin Eiseigaku Zasshi. 2008 49(1):56–62. Abstract
6. Bekiroglu S, Myrberg O, Ostman K, Ek M, Arvidsson T, Rundlöf T, Hakkarainen B, Validation of a quantitative NMR method for suspected counterfeit products exemplified on determination of benzethonium chloride in grapefruit seed extracts. J Pharm Biomed Anal. 2008 47(4-5):958–961. Abstract
13. Takeoka GR, Dao LT, Wong RY, Harden LA. Identification of benzalkonium chloride in commercial grapefruit seed extracts. J Agric Food Chem. 2005 53(19):7630–6. Abstract
14. Todd Caldecott. Grapefruit seed extract antibiotic activity is due to preservative compounds. Townsend Letter for Doctors and Patients. 2005. Article
15. Reagor L, Gusman J, McCoy L, Carino E, Heggers JP. The effectiveness of processed grapefruit-seed extract as an antibacterial agent: I. An in vitro agar assay. J Altern Complement Med. 2002 Jun;8(3):325-32. Abstract
16. Heggers JP, Cottingham J, Gusman J, Reagor L, McCoy L, Carino E, Cox R, Zhao JG. The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity. J Altern Complement Med. 2002 Aug;8(4):521. Reagor Lana, corrected to Reagor Lee. Abstract
17. Cvetnic Z, Vladimir-Knezevic S. Antimicrobial activity of grapefruit seed and pulp ethanolic extract. Acta Pharm. 2004 Sep;54(3):243-5. Abstract
18. Ganzera M, Aberham A, Stuppner H. Development and validation of an HPLC/UV/MS method for simultaneous determination of 18 preservatives in grapefruit seed extract. Institute of Pharmacy, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria. J Agric Food Chem. 2006 May 31;54(11):3768-72. Abstract
19. Kampf G, Kramer A. Epidemiologic background of hand hygiene and evaluation of the most important agents for scrubs and rubs. Bode Chemie GmbH & Co., Scientific Affairs, Melanchthonstrasse 27, 22525 Hamburg, Germany. Clin Microbiol Rev. 2004 Oct;17(4):863-93. Abstract
20. Sakamoto S, Sato K, Maitani T, Yamada T. Analysis of components in natural food additive “grapefruit seed extract” by HPLC and LC/MS. Bull. Natl. Inst. Health Sci. 1996, 114:38–42. Abstract
21. Chiambaretta F, Pouliquen P, Rigal D. Allergy and preservatives. Apropos of 3 cases of allergy to benzalkonium chloride. J Fr Ophtalmol. 1997;20(1):8-16. Abstract
22. Liu H, Routley I, Teichmann KD. Toxic endothelial cell destruction from intraocular benzalkonium chloride. J Cataract Refract Surg. 2001 Nov;27(11):1746-50. Comment in: J Cataract Refract Surg. 2003 Feb;29(2):233. Abstract
23. Eleraky, N.Z., Potgieter, L.N., Kennedy, M.A. Virucidal efficacy of four new disinfectants. J Am Anim Hosp Assoc. 2002 38(3):231–4. Abstract
38. Brandin H, Myrberg O, Rundlöf T, Arvidsson AK, Brenning G. Adverse effects by artificial grapefruit seed extract products in patients on warfarin therapy. Eur J Clin Pharmacol. 2007 Jun;63(6):565-70. Abstract