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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.<ref name=BrandStudy>{{cite journal |author=Reagor L, Gusman J, McCoy L, Carino E, Heggers JP |title=The effectiveness of processed grapefruit-seed extract as an antibacterial agent: I. An in vitro agar assay |journal=J Altern Complement Med |volume=8 |issue=3 |pages=325–32 |year=2002 |month=June |pmid=12165190 |doi=10.1089/10755530260128014 }}</ref><ref name=BrandTest>{{cite journal |author=Heggers JP, Cottingham J, Gusman J, ''et al.'' |title=The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity |journal=J Altern Complement Med |volume=8 |issue=3 |pages=333–40 |year=2002 |month=June |pmid=12165191 |doi=10.1089/10755530260128023 }}</ref><ref name=EthanolGSE>{{cite journal |author=Cvetni&#x107; Z, Vladimir-Knezevi&#x107; S |title=Antimicrobial activity of grapefruit seed and pulp ethanolic extract |journal=Acta Pharm |volume=54 |issue=3 |pages=243–50 |year=2004 |month=September |pmid=15610620 }}</ref> The preliminary studies for the antimicrobial effect state that the Citricidal commercial brand of GSE was used for testing.<ref name=BrandStudy/><ref name=BrandTest/> 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.<ref name=Preservatives>{{cite journal |author=Ganzera M, Aberham A, Stuppner H |title=Development and validation of an HPLC/UV/MS method for simultaneous determination of 18 preservatives in grapefruit seed extract |journal=J. Agric. Food Chem. |volume=54 |issue=11 |pages=3768–72 |year=2006 |month=May |pmid=16719494 |doi=10.1021/jf060543d }}</ref> 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.<ref name=Contamination>{{cite journal |author=Takeoka G, Dao L, Wong RY, Lundin R, Mahoney N |title=Identification of benzethonium chloride in commercial grapefruit seed extracts |journal=J. Agric. Food Chem. |volume=49 |issue=7 |pages=3316–20 |year=2001 |month=July |pmid=11453769 |doi=10.1021/jf010222w }}</ref> 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.<ref name=Contamination/> It is inconceivable that the preservative benzethonium chloride is formed during any extraction and/or processing of grapefruit seeds and pulp.<ref name=Contamination/> 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.<ref name=Contamination/> Another in vitro study claimed GSE had antibacterial properties.<ref name=EthanolGSE/> As with the branded in vitro test<ref name=BrandStudy/><ref name=BrandTest/> this extract was contaminated.<ref name=Contamination/> The ethanolic grapefruit seed and pulp extract tested was prepared or contaminated with ethanol, a chemical solvent used in the extraction process.<ref name=EthanolGSE/> [[Ethanol]], also known as ethyl alcohol, is effective in inhibiting bacteria.<ref name="Ethanol_Alcohol_Effectiveness">{{cite journal |author=Kampf G, Kramer A |title=Epidemiologic Background of Hand Hygiene and Evaluation of the Most Important Agents for Scrubs and Rubs |journal=Clin. Microbiol. Rev. |volume=17 |issue=4 |pages=863–93, table of contents |year=2004 |month=October |pmid=15489352 |pmc=523567 |doi=10.1128/CMR.17.4.863-893.2004 }}</ref>
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.<ref name=BrandStudy>{{cite journal |author=Reagor L, Gusman J, McCoy L, Carino E, Heggers JP |title=The effectiveness of processed grapefruit-seed extract as an antibacterial agent: I. An in vitro agar assay |journal=J Altern Complement Med |volume=8 |issue=3 |pages=325–32 |year=2002 |month=June |pmid=12165190 |doi=10.1089/10755530260128014 }}</ref><ref name=BrandTest>{{cite journal |author=Heggers JP, Cottingham J, Gusman J, ''et al.'' |title=The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity |journal=J Altern Complement Med |volume=8 |issue=3 |pages=333–40 |year=2002 |month=June |pmid=12165191 |doi=10.1089/10755530260128023 }}</ref><ref name=EthanolGSE>{{cite journal |author=Cvetni&#x107; Z, Vladimir-Knezevi&#x107; S |title=Antimicrobial activity of grapefruit seed and pulp ethanolic extract |journal=Acta Pharm |volume=54 |issue=3 |pages=243–50 |year=2004 |month=September |pmid=15610620 }}</ref> The preliminary studies for the antimicrobial effect state that the Citricidal commercial brand of GSE was used for testing.<ref name=BrandStudy/><ref name=BrandTest/> 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.<ref name=Preservatives>{{cite journal |author=Ganzera M, Aberham A, Stuppner H |title=Development and validation of an HPLC/UV/MS method for simultaneous determination of 18 preservatives in grapefruit seed extract |journal=J. Agric. Food Chem. |volume=54 |issue=11 |pages=3768–72 |year=2006 |month=May |pmid=16719494 |doi=10.1021/jf060543d }}</ref> 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.<ref name=Contamination>{{cite journal |author=Takeoka G, Dao L, Wong RY, Lundin R, Mahoney N |title=Identification of benzethonium chloride in commercial grapefruit seed extracts |journal=J. Agric. Food Chem. |volume=49 |issue=7 |pages=3316–20 |year=2001 |month=July |pmid=11453769 |doi=10.1021/jf010222w }}</ref> 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.<ref name=Contamination/> It is inconceivable that the preservative benzethonium chloride is formed during any extraction and/or processing of grapefruit seeds and pulp.<ref name=Contamination/> 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.<ref name=Contamination/> Another in vitro study claimed GSE had antibacterial properties.<ref name=EthanolGSE/> As with the branded in vitro test<ref name=BrandStudy/><ref name=BrandTest/> this extract was contaminated.<ref name=Contamination/> The ethanolic grapefruit seed and pulp extract tested was prepared or contaminated with ethanol, a chemical solvent used in the extraction process.<ref name=EthanolGSE/> [[Ethanol]], also known as ethyl alcohol, is effective in inhibiting bacteria.<ref name="Ethanol_Alcohol_Effectiveness">{{cite journal |author=Kampf G, Kramer A |title=Epidemiologic Background of Hand Hygiene and Evaluation of the Most Important Agents for Scrubs and Rubs |journal=Clin. Microbiol. Rev. |volume=17 |issue=4 |pages=863–93, table of contents |year=2004 |month=October |pmid=15489352 |pmc=523567 |doi=10.1128/CMR.17.4.863-893.2004 }}</ref>

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 [[paraben|methylparaben]].<ref name=Pharmazie>{{cite journal |author=von Woedtke T, Schlüter B, Pflegel P, Lindequist U, Jülich WD |title=Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained |journal=Pharmazie |volume=54 |issue=6 |pages=452–6 |year=1999 |month=June |pmid=10399191 }}</ref><ref name=Adulteration>{{cite journal |author=Takeoka GR, Dao LT, Wong RY, Harden LA |title=Identification of benzalkonium chloride in commercial grapefruit seed extracts |journal=J. Agric. Food Chem. |volume=53 |issue=19 |pages=7630–6 |year=2005 |month=September |pmid=16159196 |doi=10.1021/jf0514064 }}</ref><ref name=Study>{{cite journal |author=Sakamoto S, Sato K, Maitani T, Yamada T |title=[Analysis of components in natural food additive "grapefruit seed extract" by HPLC and LC/MS] |language=Japanese |journal=Eisei Shikenjo Hokoku |volume= |issue=114 |pages=38–42 |year=1996 |pmid=9037863 }}</ref> Some samples were shown to contain up to 22% benzalkonium chloride by weight, despite the known [[allergy|allergenicity]]<ref name=Alergenicity>{{cite journal |author=Chiambaretta F, Pouliquen P, Rigal D |title=[Allergy and preservatives. Apropos of 3 cases of allergy to benzalkonium chloride] |language=French |journal=J Fr Ophtalmol |volume=20 |issue=1 |pages=8–16 |year=1997 |pmid=9099278 }}</ref> and [[toxicity]]<ref name=Toxicity>{{cite journal |author=Liu H, Routley I, Teichmann KD |title=Toxic endothelial cell destruction from intraocular benzalkonium chloride |journal=J Cataract Refract Surg |volume=27 |issue=11 |pages=1746–50 |year=2001 |month=November |pmid=11709246 |doi=10.1016/S0886-3350(01)01067-7 }}
</ref> of the compound at higher doses.<ref name=Adulteration/> 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.<ref name=Pharmazie/> Although citrus seed extract is sold in health food markets,<ref name=Adulteration/> there is no good evidence for any natural antimicrobial activity.<ref name=Pharmazie/><ref name="preservative_compounds"/>

A study that examined the antiviral properties of GSE found that GSE had no efficacy as a disinfectant for [[feline calicivirus]] and [[feline panleukopenia|feline parvovirus]].<ref name="Virucidal_Efficacy">{{cite journal |author=Eleraky NZ, Potgieter LN, Kennedy MA |title=Virucidal efficacy of four new disinfectants |journal=J Am Anim Hosp Assoc |volume=38 |issue=3 |pages=231–4 |year=2002 |pmid=12022408 }}</ref>
Grapefruit seed extract has been advocated to be a powerful [[antimicrobial]] with proven activity against [[bacteria]] and [[fungus|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 skin care|natural personal care]] manufacturers, studies asserted that the universal antimicrobial benefits associated with GSE are merely from the presence of synthetic [[preservative]]s. [[Nature|Natural]] GSE has no antimicrobial properties.<ref name=Pharmazie/><ref name=Preservatives/> Newer studies found many commercial grapefruit seed extracts contaminated with synthetic preservatives.<ref name="Pharmazie_2007">{{cite journal |author=Avula B, Dentali S, Khan IA |title=Simultaneous identification and quantification by liquid chromatography of benzethonium chloride, methyl paraben and triclosan in commercial products labeled as grapefruit seed extract |journal=Pharmazie |volume=62 |issue=8 |pages=593–6 |year=2007 |month=August |pmid=17867553 }}</ref><ref name="synthetic_disinfectants">{{cite journal |author=Sugimoto N, Tada A, Kuroyanagi M, ''et al.'' |title=[Survey of synthetic disinfectants in grapefruit seed extract and its compounded products] |language=Japanese |journal=Shokuhin Eiseigaku Zasshi |volume=49 |issue=1 |pages=56–62 |year=2008 |month=February |pmid=18344660 |doi=10.3358/shokueishi.49.56 }}</ref><ref name="counterfeit_products">{{cite journal |author=Bekiroglu S, Myrberg O, Ostman K, ''et al.'' |title=Validation of a quantitative NMR method for suspected counterfeit products exemplified on determination of benzethonium chloride in grapefruit seed extracts |journal=J Pharm Biomed Anal |volume=47 |issue=4–5 |pages=958–61 |year=2008 |month=August |pmid=18456447 |doi=10.1016/j.jpba.2008.03.021 }}</ref> In a 2007 study the main synthetic antimicrobial agent identified in commercial GSE samples was benzethonium chloride.<ref name="Pharmazie_2007"/> In a 2008 study synthetic disinfectants such as benzethonium or benzalkonium chloride were identified in most of the commercial GSE products.<ref name="synthetic_disinfectants"/> In a 2008 study suspected counterfeit products were determined to contain benzethonium chloride in grapefruit seed extract samples.<ref name="counterfeit_products"/>


== Methodology ==
== Methodology ==

Revision as of 16:26, 13 November 2012

Grapefruit seed extract (GSE), also known as citrus seed extract, is a liquid derived from the seeds, pulp, and white membranes of grapefruit.[1] Self-made natural GSE processed in the laboratory without solvents or synthetic agents is prepared by grinding the grapefruit seed and juiceless pulp, then mixing with glycerin.[1] Commercially available GSE sold to consumers are made from the seed, pulp, glycerin, and synthetic preservatives all blended together.[1] Grapefruit seed extract is sold as a food supplement and used in cosmetics because it is a claimed natural antimicrobial.[2]

An early proponent was Dr. Jacob Harich (1919–1996).[3] A long time promoter of GSE was Aubrey Hampton, the founder of Aubrey Organics.[4] Some marketers of GSE affirm this extract to be a safe, natural, and an effective preservative.[5] This extract has been stated by some practitioners of alternative medicine to possess antibacterial, antiviral, and antifungal properties.[3] It has been recommended by some nutritionists for the treatment of candidiasis, earache, throat infections, and diarrhea.[3] GSE is promoted at health food shops and on the internet.[6][7]

There are conflicting scientific demonstrations of the efficacy of GSE.[1] Suspicions about the true nature of the active compounds in GSEs arose when synthetic additives were found in commercial products.[2] Suspected counterfeit grapefruit seed extracts were adulterated with synthetic preservatives.[8][9][10] When preservatives were not present in some of the extracts, laboratory tests found the natural extracts had no natural antimicrobial attributes of their own.[5] Some manufacturers of GSE have stated that their extract has compounds nearly identical to benzethonium chloride, but a 2001 study supervised by chemist G. Takeoka has documented that commercial GSE preparations contain the synthetic compound benzethonium chloride that could not have been made from GSE.[5]

History

The grapefruit is a subtropical citrus tree grown for its fruit which was originally named the "forbidden fruit" of Barbados.[11] The fruit was first documented in 1750 by Rev. Griffith Hughes describing specimens from Barbados.[12] All parts of the fruit have uses. The fruit is mainly consumed for a tangy juice.[13] The peel is expressed into an aromatherapy oil[14] and is also a source of dietary fiber.[15] The seed and pulp as a by-product of the juice industry is sold as cattle feed[16] and is manufactured for use to make an extract.[1] GSE was originally developed by Dr. Jacob Harich, a nuclear physicist. In 1963, he journeyed to Florida, the heart of grapefruit country in the U.S., and began researching and later marketing of GSE.[3] Aubrey Hampton, founder of Aubrey Organics, has promoted citrus seed extract, a component in "Aubrey’s Preservative", for more than 25 years.[4] Today, GSE is mostly promoted at health food shops and on the internet.[6][7]

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]

Methodology

Grapefruit seed extracts are added to cosmetics, food supplements, and pesticides for their antimicrobial effect, but suspicions about the true nature of the active compounds in GSEs arose when synthetic additives were found in commercial products.[2] Various analytical methods were developed to determine the constituents or compounds in GSE samples which include particle-induced x-ray emission (PIXE),[5] electrospray ionization mass spectrometry (ESI-MS),[5] high performance liquid chromatography (HPLC),[2] liquid chromatography-mass spectrometry (LC-MS),[9] and nuclear magnetic resonance (NMR) analysis.[10]

Properties

There is evidence that the extract of citrus grapefruit seed has antioxidant properties.[21][22] Analysis shows the constituents of the seed extract and pulp are flavonoids,[23][24] ascorbic acid (commonly known as vitamin C[25][26][27]), tocopherols, citric acid,[21] limonoids,[28][29][30] sterols, and minerals.[31] A study suggests the consumption of the bioactive compounds found in grapefruit seed and pulp may help suppress the development of colon cancer.[32] Another study showed the flavonoid naringin is an excellent plasma lipid lowering and plasma antioxidant active elevating flavonone.[33]

Preparations

Self-made pure GSE processed without solvents is prepared by grinding the grapefruit seed and juiceless pulp, then mixing with glycerin.[1]

Commercially available GSE sold to consumers are made from the seed, pulp, glycerin, and synthetic preservatives all blended together.[1]

Precautions

Grapefruit can have a number of interactions with certain drugs, increasing the potency of many compounds,[34] including warfarin (coumadin).[35] Grapefruit has components that inhibit the CYP3A4 enzyme in the intestine.[34] Thus, it is this effect that increases the rate of absorption of several drugs.[36] There are concerns about the safety of ingesting synthetic preservatives found in grapefruit seed extract.[7]

Controversy

GSE usage has been popularized by many companies within the scope of the health food industry.[5] There are books exclusively dedicated to GSE.[3][37][38] This extract is promoted by marketers on the internet, there are health food stores that recommend its use, and proponents maintain its safe.[5][7] 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][2][5][6][39][35]

GSE is marketed as an all-natural and perfectly safe health food product, when it is neither. Various Citrus species have been used as a food and medicine in Chinese and Ayurvedic medicine for thousands of years. While they have many many benefits, neither Chinese nor Ayurvedic medicine has ever advocated the use of Grapefruit seed or any other Citrus seed in acute infectious disease: this alone should provide some clue as to its effects or lack thereof.

— Todd Caldecott, [7]

See also

References

  1. ^ a b c d e f g h Cite error: The named reference Pharmazie was invoked but never defined (see the help page).
  2. ^ a b c d e f Ganzera M, Aberham A, Stuppner H (2006). "Development and validation of an HPLC/UV/MS method for simultaneous determination of 18 preservatives in grapefruit seed extract". J. Agric. Food Chem. 54 (11): 3768–72. doi:10.1021/jf060543d. PMID 16719494. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  3. ^ a b c d e Sims, Judith. Gale Encyclopedia of Alternative Medicine. Available in e-book format. Thomson Gale. 2001.
  4. ^ a b Melissa Meisel. Cosmetics Go Green. Happi, Rodman Publishing, June 2007.
  5. ^ a b c d e f g h i j k l m Takeoka G, Dao L, Wong RY, Lundin R, Mahoney N (2001). "Identification of benzethonium chloride in commercial grapefruit seed extracts". J. Agric. Food Chem. 49 (7): 3316–20. doi:10.1021/jf010222w. PMID 11453769. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  6. ^ a b c Cite error: The named reference Adulteration was invoked but never defined (see the help page).
  7. ^ a b c d e Todd Caldecott. Grapefruit seed extract antibiotic activity is due to preservative compounds. Townsend Letter for Doctors and Patients. 2005.
  8. ^ Cite error: The named reference Pharmazie_2007 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference synthetic_disinfectants was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference counterfeit_products was invoked but never defined (see the help page).
  11. ^ Dowling, Curtis F.; Morton, Julia Frances (1987). Fruits of warm climates. Miami, Fla: J.F. Morton. pp. 152–8. ISBN 0-9610184-1-0.{{cite book}}: CS1 maint: multiple names: authors list (link)
  12. ^ Michael Quinion. World Wide Words: Questions & Answers; Grapefruit. 2009.
  13. ^ Fellers PJ, Nikdel S, Lee HS (1990). "Nutrient content and nutrition labeling of several processed Florida citrus juice products". J Am Diet Assoc. 90 (8): 1079–84. PMID 2380455. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  14. ^ Worwood, Valerie Ann (1991). The complete book of essential oils and aromatherapy. Novato, Calif: New World Library. ISBN 0-931432-82-0.
  15. ^ Cerda JJ, Robbins FL, Burgin CW, Baumgartner TG, Rice RW (1988). "The effects of grapefruit pectin on patients at risk for coronary heart disease without altering diet or lifestyle". Clin Cardiol. 11 (9): 589–94. doi:10.1002/clc.4960110902. PMID 3229016. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  16. ^ Arthington JD, Kunkle WE, Martin AM (2002). "Citrus pulp for cattle". Vet. Clin. North Am. Food Anim. Pract. 18 (2): 317–26, vii. doi:10.1016/S0749-0720(02)00023-3. PMID 12235663. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  17. ^ a b c Reagor L, Gusman J, McCoy L, Carino E, Heggers JP (2002). "The effectiveness of processed grapefruit-seed extract as an antibacterial agent: I. An in vitro agar assay". J Altern Complement Med. 8 (3): 325–32. doi:10.1089/10755530260128014. PMID 12165190. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  18. ^ a b c Heggers JP, Cottingham J, Gusman J; et al. (2002). "The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity". J Altern Complement Med. 8 (3): 333–40. doi:10.1089/10755530260128023. PMID 12165191. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  19. ^ a b c Cvetnić Z, Vladimir-Knezević S (2004). "Antimicrobial activity of grapefruit seed and pulp ethanolic extract". Acta Pharm. 54 (3): 243–50. PMID 15610620. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  20. ^ Kampf G, Kramer A (2004). "Epidemiologic Background of Hand Hygiene and Evaluation of the Most Important Agents for Scrubs and Rubs". Clin. Microbiol. Rev. 17 (4): 863–93, table of contents. doi:10.1128/CMR.17.4.863-893.2004. PMC 523567. PMID 15489352. {{cite journal}}: Unknown parameter |month= ignored (help)
  21. ^ a b Armando C, Maythe S, Beatriz NP (1997). "Antioxidant activity of grapefruit seed extract on vegetable oils". Journal of the Science of Food and Agriculture. 77 (4): 463–7. doi:10.1002/(SICI)1097-0010(199808)77:4<463::AID-JSFA62>3.0.CO;2-1. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  22. ^ Giamperi L, Fraternale D, Bucchini A, Ricci D (2004). "Antioxidant activity of Citrus paradisi seeds glyceric extract". Fitoterapia. 75 (2): 221–4. doi:10.1016/j.fitote.2003.12.010. PMID 15030930. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  23. ^ Drewnowski A, Gomez-Carneors C (2000). "Bitter taste, phytonutrients, and consumer: a review". Am. J. Clin. Nutr. 72 (6): 1424–35. PMID 11101467.
  24. ^ Tirillini B (2000). "Grapefruit: the last decade acquisitions". Fitoterapia. 71: 29–37. doi:10.1016/S0367-326X(00)00176-3. PMID 10930710.
  25. ^ Andrew W. Saul, Ph.D. Vitamin C Has Been Known To Fight 30 Major Diseases... For Over 50 Years. Orthomolecular Medicine News Service. March 15, 2006.
  26. ^ Vitamin C. American Cancer Society. 2009.
  27. ^ The World's Healthiest Foods; Grapefruit. The George Mateljan Foundation. 2009.
  28. ^ Bennett RD, Hasegava S, Herman Z (1989). "Glucosides of acidic limonoids in citrus". Phytochemistry. 28 (10): 2777–81. doi:10.1016/S0031-9422(00)98087-7.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  29. ^ Ohta H, Fong CH, Berhow M, Hesegawa (1993). "Thin-layer and high-performance liquid chromatographic analyses of limonoids and limonoid glucosides in citrus seeds". J. Chromatogr. 639 (2): 295–302. doi:10.1016/0021-9673(93)80266-B.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  30. ^ Braddock RJ, Bryan CR (2001). "Extraction parameters and capillary electrophorisis analysis of limonin glucoside and phlorin in citrus products". J. Agric. Food Chem. 49 (12): 5982–8. doi:10.1021/jf010737n. PMID 11743796.
  31. ^ Tushiswili LS, Durmishidze SV, Sulaberidze KV (1983). "Sterols of grapefruit, orange, mandarin pulps (Citrus paradisi, Citrus sinensis, Citrus unshiu)". Chem. Nat. Comp. 18: 445–7.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  32. ^ Vanamala J, Leonardi T, Patil BS; et al. (2006). "Suppression of colon carcinogenesis by bioactive compounds in grapefruit". Carcinogenesis. 27 (6): 1257–65. doi:10.1093/carcin/bgi318. PMID 16387741. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  33. ^ Gorinstein S, Leontowicz H, Leontowicz M; et al. (2005). "Changes in plasma lipid and antioxidant activity in rats as a result of naringin and red grapefruit supplementation". J. Agric. Food Chem. 53 (8): 3223–8. doi:10.1021/jf058014h. PMID 15826081. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  34. ^ a b Bakalar, Nicholas. Experts Reveal the Secret Powers of Grapefruit Juice. The New York Times. March 21, 2006.
  35. ^ a b Brandin H, Myrberg O, Rundlöf T, Arvidsson AK, Brenning G (2007). "Adverse effects by artificial grapefruit seed extract products in patients on warfarin therapy". Eur. J. Clin. Pharmacol. 63 (6): 565–70. doi:10.1007/s00228-007-0289-1. PMID 17468864. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  36. ^ He K, Iyer KR, Hayes RN, Sinz MW, Woolf TF, Hollenberg PF (1998). "Inactivation of cytochrome P450 3A4 by bergamottin, a component of grapefruit juice". Chem. Res. Toxicol. 11 (4): 252–9. doi:10.1021/tx970192k. PMID 9548795. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  37. ^ Sharamon, S., Baginski, B.J. The Healing Power of Grapefruit Seed. Lotus Press, Wisconsin. 1996. ISBN 0-914955-27-6
  38. ^ Allan Sachs (1997). The authoritative guide to grapefruit seed extract. Mendocino, CA: LifeRhythm. ISBN 0-940795-17-5.
  39. ^ Cite error: The named reference Study was invoked but never defined (see the help page).
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