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'''Grapefruit seed extract''' (GSE), also known as '''citrus seed extract''', is a liquid derived from the [[seed]]s, [[citrus#Uses|pulp]], and [[juice vesicles|white membranes]] of [[grapefruit]].<ref name=Pharmazie/> 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.<ref name=Pharmazie/> Commercially available GSE sold to consumers are made from the seed, pulp, glycerin, and synthetic preservatives all blended together.<ref name=Pharmazie/> Grapefruit seed extract is sold as a [[dietary supplement|food supplement]] and used in [[cosmetics]] because it is a claimed natural [[antimicrobial]].<ref name=Preservatives/>
'Grapefruit Seed Extract is a liquid substance extracted from the fruit and seeds of grapefruit, a sub-tropical citrus tree that grows in abundance throughout many countries. The extract from grapefruit seed was first documented for its medicinal uses in 1972 by Dr. Jacob Harich, a physicist who noticed its traditional use as a disinfectant in a multitude of countries.¹ Many traditional societies, from South America to Europe, to Asia have used the extract to clean the skin, hair, and home surfaces. These societies also valued the extract as a powerful anti-viral and bacterial.5


An early proponent was Dr. Jacob Harich (1919&ndash;1996).<ref name="E-Book"/> A long time promoter of GSE was Aubrey Hampton, the founder of Aubrey Organics.<ref name="Happi"/> Some marketers of GSE affirm this extract to be a safe, natural, and an effective preservative.<ref name=Contamination/> This [[herbal extract|extract]] has been stated by some practitioners of [[alternative medicine]] to possess [[antiseptic|antibacterial]], [[antiviral drug|antiviral]], and [[antifungal drug|antifungal]] properties.<ref name="E-Book"/> It has been recommended by some [[nutritionist]]s for the treatment of [[candidiasis]], [[otalgia|earache]], throat infections, and [[diarrhea]].<ref name="E-Book"/> GSE is promoted at [[health food store|health food shops]] and on the [[internet]].<ref name=Adulteration/><ref name="preservative_compounds"/>
The Health Benefits of Grapefruit Seed Extract
Grapefruit Seed Extract (GSE) has very high amounts of disease-fighting, free-radical eliminating antioxidants and phytonutrients called bioflavonoids. One of these powerful bioflavanoids (plant antioxidants) include the chemical component hesperidin, a well-known natural immune-system stimulator and booster.4


There are conflicting scientific demonstrations of the efficacy of GSE.<ref name=Pharmazie/> Suspicions about the true nature of the active compounds in GSEs arose when synthetic additives were found in commercial products.<ref name=Preservatives/> Suspected counterfeit grapefruit seed extracts were adulterated with [[chemical synthesis|synthetic]] [[preservative]]s.<ref name="Pharmazie_2007"/><ref name="synthetic_disinfectants"/><ref name="counterfeit_products"/> When preservatives were not present in some of the extracts, laboratory tests found the natural extracts had no natural antimicrobial attributes of their own.<ref name=Contamination/> 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.<ref name=Contamination/>


== History ==


The grapefruit is a subtropical [[citrus]] [[tree]] grown for its [[fruit]] which was originally named the "[[forbidden fruit]]" of [[Barbados]].<ref name="Forbidden_Fruit">{{cite book |author=Dowling, Curtis F.; Morton, Julia Frances |title=Fruits of warm climates |publisher=J.F. Morton |location=Miami, Fla |year=1987 |pages=152–8 |isbn=0-9610184-1-0|url=http://www.hort.purdue.edu/newcrop/morton/grapefruit.html}}</ref> The fruit was first documented in 1750 by Rev. [[Griffith Hughes]] describing specimens from Barbados.<ref name="Q_A:Grapefruit">Michael Quinion. [http://www.worldwidewords.org/qa/qa-gra3.htm World Wide Words: Questions & Answers; Grapefruit]. 2009.</ref> All parts of the fruit have uses. The fruit is mainly consumed for a tangy [[juice]].<ref name="Citrus_Juice">{{cite journal |author=Fellers PJ, Nikdel S, Lee HS |title=Nutrient content and nutrition labeling of several processed Florida citrus juice products |journal=J Am Diet Assoc |volume=90 |issue=8 |pages=1079–84 |year=1990 |month=August |pmid=2380455 }}</ref> The peel is expressed into an [[aromatherapy]] [[essential oil|oil]]<ref name=Valerie>{{cite book |author=Worwood, Valerie Ann |title=The complete book of essential oils and aromatherapy |publisher=New World Library |location=Novato, Calif |year=1991 |isbn=0-931432-82-0 }}</ref> and is also a source of [[dietary fiber]].<ref name="Pectin_Benefits">{{cite journal |author=Cerda JJ, Robbins FL, Burgin CW, Baumgartner TG, Rice RW |title=The effects of grapefruit pectin on patients at risk for coronary heart disease without altering diet or lifestyle |journal=Clin Cardiol |volume=11 |issue=9 |pages=589–94 |year=1988 |month=September |pmid=3229016 |doi=10.1002/clc.4960110902 }}</ref> The seed and pulp as a by-product of the juice industry is sold as cattle feed<ref name="Cattle_Feed">{{cite journal |author=Arthington JD, Kunkle WE, Martin AM |title=Citrus pulp for cattle |journal=Vet. Clin. North Am. Food Anim. Pract. |volume=18 |issue=2 |pages=317–26, vii |year=2002 |month=July |pmid=12235663 |doi=10.1016/S0749-0720(02)00023-3 }}</ref> and is manufactured for use to make an extract.<ref name=Pharmazie/> GSE was originally developed by Dr. Jacob Harich, a nuclear physicist. In 1963, he journeyed to Florida, the [[heart (symbol)|heart]] of grapefruit country in the U.S., and began researching and later [[marketing]] of GSE.<ref name="E-Book"/> Aubrey Hampton, founder of Aubrey Organics, has promoted citrus seed extract, a component in "Aubrey’s Preservative", for more than 25 years.<ref name="Happi">Melissa Meisel. [http://www.happi.com/articles/2007/06/cosmetics-go-green Cosmetics Go Green]. Happi, Rodman Publishing, June 2007.</ref> Today, GSE is mostly promoted at [[health food store|health food shops]] and on the [[internet]].<ref name=Adulteration/><ref name="preservative_compounds"/>
Chemical analysis of grapefruit seed extract shows additional antioxidant constituents including Vitamin C, sterols, tocopherols, citric acid, liminoids, and other trace minerals. Perhaps most exciting in regard to GSE's health benefits is its anti-cancer potentials. Studies done on the compounds in GSE's seed and pulp have found that these bioactive agents may be able to inhibit the occurrence of colon cancer. 6


== Efficacy ==
A recent study done by Microbiologists from the University of Georgia found that GSE was a very effective non-toxic disinfectant. Sadly, commonly-used disinfectant have high levels of toxicity and are harmful to humans, animals and the environment. The same study found that GSE demonstrates a "wide spectrum of activity," including antiviral, antimycotic, and antiprotozoan capacities against many bacteria and viruses, including E.Coli.¹ It was also found to be an effective cleanser as a a pre-surgical soap.¹


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>
Another recent study from The Journal of Alternative and Complementary Medicine found that grapefruit-seed extract was effective in killing over "800 bacterial and viral strains, 100 strains of fungus, and a large number of single and multi-celled parasites."² No other naturally-occuring anti-microbial can come close to these results.


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 }}
Grapefruit Seed Extract is associated with the following potential health benefits:
</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>
Powerful natural antiseptic.
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"/>
Antiviral and anti-fungal agent.
Possible anti-cancer properties.6
Promotes the healing of wounds and scar tissue.
Possible cholesterol-lowering properties due to the presence of the flavanoid naringin (a well-known plasma lipid reducer and plasma antioxidant activator).7
Excellent remedy for toenail fungal infections.4
Treatment for sinus, vaginal and topical skin infections.
Evironmentally-friendly fruit and vegetable wash for removing toxins.³
Effective preventative for Candida and other forms of yeast infection.4
Inhibits the formation of harmful intestinal organisms, including Giardia, without reducing levels of healthy bowel flora.4,5
Acts as a natural preservative for cosmetics.
Can replace chlorine in swimming pools, public baths, water and sewage treatment centers, and it also used as a general water-purifying mechanism.5
May reduce chances of developing coronary heart disease in high-risk patients due to high pectin content in Grapefruit seed extract.8
Possible anti-biotic activity.
Aids to alkalize the body, and is one of the world's most alkaline forming foods, helping to stabilize acidic pH levels, a central component for health rejuvenation.
Great general immune system booster.
Other Home-Friendly Benefits of Grapefruit Seed Extract
An excellent extract to have on hand while traveling into foreign countries, GSE acts as a natural germ-killer and an effective preventative mechanism for food borne illnesses that cause diarrhea and dysentery. It is also useful for our pets, and can be applied in both internal and external infections of the skin, including fleas. It is also highly useful for the modern eco-conscious gardener, and can used to remove fungus and mold from tools and supplies. It is also a great bug and plant spray. Grapefruit seed extract can be used to clean surfaces and even sprinkled into soaps for an added anti-microbial and viral effects.


== Methodology ==
REFERENCES:


Grapefruit seed extracts are added to [[cosmetics]], [[dietary supplement|food supplements]], and [[pesticide#Alternatives|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.<ref name=Preservatives/> Various [[analytical chemistry|analytical methods]] were developed to determine the constituents or compounds in GSE samples which include [[particle-Induced X-ray Emission|particle-induced x-ray emission]] (PIXE),<ref name=Contamination/> [[electrospray ionization|electrospray ionization mass spectrometry]] (ESI-MS),<ref name=Contamination/> [[high performance liquid chromatography]] (HPLC),<ref name=Preservatives/> [[liquid chromatography-mass spectrometry]] (LC-MS),<ref name="synthetic_disinfectants"/> and [[nuclear magnetic resonance]] (NMR) analysis.<ref name="counterfeit_products"/>
HYPERLINK "http://www.nutriteam.com/index2.html" http://www.nutriteam.com/index2.html

The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity. . 2002 Jun;8(3):333-40. J Altern Complement Med 2002 Aug;8(4):521. Reagor Lana [corrected to Reagor Lee]. HYPERLINK "http://www.ncbi.nlm.nih.gov/pubmed/12165191"
== Properties ==
The Best Supplements for Your Health By Donald Goldberg, Arnold Gitomer, Robert Abel. p.185. http://books.google.com/books?id=eLPakvLPpVgC&pg=PA185&dq=grapefruit+seed+extract+uses

Earl Mindell's Supplement Bible. Earl Mindell. p. 69. http://books.google.com/books?id=5lnV9G30MIUC&pg=PA68&dq=grapefruit+seed+extract+benefits
There is evidence that the extract of citrus grapefruit seed has [[antioxidant]] properties.<ref name=Extract>{{cite journal |author=Armando C, Maythe S, Beatriz NP |title=Antioxidant activity of grapefruit seed extract on vegetable oils |journal=Journal of the Science of Food and Agriculture |volume=77 |issue=4 |pages=463–7 |year=1997 |month=December |url=http://www3.interscience.wiley.com/cgi-bin/abstract/10007270/ABSTRACT |doi=10.1002/(SICI)1097-0010(199808)77:4<463::AID-JSFA62>3.0.CO;2-1}}</ref><ref name="Antioxidant_Activity">{{cite journal |author=Giamperi L, Fraternale D, Bucchini A, Ricci D |title=Antioxidant activity of Citrus paradisi seeds glyceric extract |journal=Fitoterapia |volume=75 |issue=2 |pages=221–4 |year=2004 |month=March |pmid=15030930 |doi=10.1016/j.fitote.2003.12.010 }}</ref> Analysis shows the constituents of the seed extract and pulp are [[flavonoids]],<ref name=Drewnowski>{{cite journal |author=Drewnowski A, Gomez-Carneors C |title=Bitter taste, phytonutrients, and consumer: a review |journal=Am. J. Clin. Nutr. |volume=72 |pages=1424–35 |year=2000 |pmid=11101467 |issue=6 }}</ref><ref name=Tirillini>{{cite journal |author=Tirillini B |title= Grapefruit: the last decade acquisitions |journal=Fitoterapia |volume=71 |pages=29–37 |year=2000 |doi=10.1016/S0367-326X(00)00176-3 |pmid=10930710}}</ref> [[ascorbic acid]] (commonly known as [[vitamin C]]<ref name="Vitamin_C">Andrew W. Saul, Ph.D. [http://www.orthomolecular.org/resources/omns/v02n02.shtml Vitamin C Has Been Known To Fight 30 Major Diseases... For Over 50 Years]. ''Orthomolecular Medicine News Service.'' March 15, 2006.</ref><ref name="ACS_C">[http://www.cancer.org/docroot/ETO/content/ETO_5_3X_Vitamin_C.asp?sitearea=ETO Vitamin C]. ''American Cancer Society.'' 2009.</ref><ref name=WHF>[http://www.whfoods.com/genpage.php?tname=foodspice&dbid=25 The World's Healthiest Foods; Grapefruit]. ''The George Mateljan Foundation.'' 2009.</ref>), [[tocopherol]]s, [[citric acid]],<ref name=Extract/> [[limonoid]]s,<ref name="Glucosides_Of_Acidic_Limonoids">{{cite journal |author=Bennett RD, Hasegava S, Herman Z |title=Glucosides of acidic limonoids in citrus |journal=Phytochemistry |volume=28 |pages=2777–81 |year=1989 |doi=10.1016/S0031-9422(00)98087-7 |issue=10 }}</ref><ref name="Limonoide_Glucosides">{{cite journal |author=Ohta H, Fong CH, Berhow M, Hesegawa |title=Thin-layer and high-performance liquid chromatographic analyses of limonoids and limonoid glucosides in citrus seeds |journal=J. Chromatogr. |volume=639 |pages=295–302 |year=1993 |doi=10.1016/0021-9673(93)80266-B |issue=2 }}</ref><ref name=Braddock>{{cite journal |author=Braddock RJ, Bryan CR |title=Extraction parameters and capillary electrophorisis analysis of limonin glucoside and phlorin in citrus products |journal=J. Agric. Food Chem. |volume=49 |pages=5982–8 |year=2001 |doi=10.1021/jf010737n |pmid=11743796 |issue=12 }}</ref> [[sterols]], and [[minerals]].<ref name=Tushiswilli>{{cite journal |author=Tushiswili LS, Durmishidze SV, Sulaberidze KV |title=Sterols of grapefruit, orange, mandarin pulps (''Citrus paradisi, Citrus sinensis, Citrus unshiu'') |journal=Chem. Nat. Comp. |volume=18 |pages=445–7 |year=1983 }}</ref> A study suggests the consumption of the bioactive compounds found in grapefruit seed and pulp may help suppress the development of colon cancer.<ref name=Vanamala>{{cite journal |author=Vanamala J, Leonardi T, Patil BS, ''et al.'' |title=Suppression of colon carcinogenesis by bioactive compounds in grapefruit |journal=Carcinogenesis |volume=27 |issue=6 |pages=1257–65 |year=2006 |month=June |pmid=16387741 |doi=10.1093/carcin/bgi318 }}</ref> Another study showed the [[flavonoid]] naringin is an excellent plasma lipid lowering and plasma antioxidant active elevating flavonone.<ref name=Naringin>{{cite journal |author=Gorinstein S, Leontowicz H, Leontowicz M, ''et al.'' |title=Changes in plasma lipid and antioxidant activity in rats as a result of naringin and red grapefruit supplementation |journal=J. Agric. Food Chem. |volume=53 |issue=8 |pages=3223–8 |year=2005 |month=April |pmid=15826081 |doi=10.1021/jf058014h }}</ref>
The Parasite Menace. Skye Weintraub. p.160. http://books.google.com/books?id=lU3D6g3H3sUC&pg=PA160&dq=grapefruit+seed+extract

Vanamala J, Leonardi T, Patil BS, et al. (June 2006). "Suppression of colon carcinogenesis by bioactive compounds in grapefruit". Carcinogenesis 27 (6): 1257–65. http://www.ncbi.nlm.nih.gov/pubmed/16387741" 16387741
== Preparations ==
Gorinstein S, Leontowicz H, Leontowicz M, et al. (April 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. "http://www.ncbi.nlm.nih.gov/pubmed/15826081" 15826081.

Cerda JJ, Robbins FL, Burgin CW, Baumgartner TG, Rice RW (September 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. "http://www.ncbi.nlm.nih.gov/pubmed/3229016" 3229016.
Self-made pure GSE processed without solvents is prepared by grinding the grapefruit seed and juiceless pulp, then mixing with glycerin.<ref name=Pharmazie/>
Heggers JP, Cottingham J, Gusman J, et al. (June 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. PMID HYPERLINK "http://www.ncbi.nlm.nih.gov/pubmed/12165191" 12165191.

Armando C, Maythe S, Beatriz NP (December 1997). Antioxidant activity of grapefruit seed extract on vegetable oils". Journal of the Science of Food and Agriculture 77 (4): 463–7. 10.1002/(SICI)1097-0010(199808)77:4<463::AID-JSFA62>3.0.CO;2-1.
Commercially available GSE sold to consumers are made from the seed, pulp, glycerin, and synthetic preservatives all blended together.<ref name=Pharmazie/>

== Precautions ==

Grapefruit can have a [[List of drugs affected by grapefruit|number of interactions]] with certain [[drug]]s, increasing the potency of many compounds,<ref name=NYTimes/> including [[warfarin]] (coumadin).<ref name="artificial_grapefruit_seed_extract"/> Grapefruit has components that inhibit the [[CYP3A4]] enzyme in the intestine.<ref name=NYTimes>Bakalar, Nicholas. [http://www.nytimes.com/2006/03/21/health/21grap.html?ex=1300597200&en=61e834f36b9afac9&ei=5090&partner=rssuserland&emc=rss Experts Reveal the Secret Powers of Grapefruit Juice]. ''The New York Times.'' March 21, 2006.</ref> Thus, it is this effect that increases the rate of absorption of several drugs.<ref name="GSE_Drug_Effect">{{cite journal |author=He K, Iyer KR, Hayes RN, Sinz MW, Woolf TF, Hollenberg PF |title=Inactivation of cytochrome P450 3A4 by bergamottin, a component of grapefruit juice |journal=Chem. Res. Toxicol. |volume=11 |issue=4 |pages=252–9 |year=1998 |month=April |pmid=9548795 |doi=10.1021/tx970192k }}</ref> There are concerns about the [[safety]] of ingesting synthetic preservatives found in grapefruit seed extract.<ref name="preservative_compounds"/>

== Controversy ==

GSE usage has been popularized by many companies within the scope of the health food industry.<ref name=Contamination/> There are books exclusively dedicated to GSE.<ref name="E-Book">Sims, Judith. Gale Encyclopedia of Alternative Medicine. Available in e-book format. ''Thomson Gale.'' 2001.</ref><ref name="Healing_Powers">Sharamon, S., Baginski, B.J. The Healing Power of Grapefruit Seed. ''Lotus Press, Wisconsin.'' 1996. ISBN 0-914955-27-6</ref><ref name="GSE_Guide">{{cite book |author=Allan Sachs |title=The authoritative guide to grapefruit seed extract |publisher=LifeRhythm |location=Mendocino, CA |year=1997 |isbn=0-940795-17-5 }}</ref> This extract is promoted by marketers on the internet, there are health food stores that recommend its use, and proponents maintain its safe.<ref name=Contamination/><ref name="preservative_compounds">Todd Caldecott. [http://findarticles.com/p/articles/mi_m0ISW/is_259-260/ai_n13628960 Grapefruit seed extract antibiotic activity is due to preservative compounds]. Townsend Letter for Doctors and Patients. 2005.</ref> 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.<ref name=Pharmazie/><ref name=Preservatives/><ref name=Contamination/><ref name=Adulteration/><ref name=Study/><ref name="artificial_grapefruit_seed_extract">{{cite journal |author=Brandin H, Myrberg O, Rundlöf T, Arvidsson AK, Brenning G |title=Adverse effects by artificial grapefruit seed extract products in patients on warfarin therapy |journal=Eur. J. Clin. Pharmacol. |volume=63 |issue=6 |pages=565–70 |year=2007 |month=June |pmid=17468864 |doi=10.1007/s00228-007-0289-1 }}</ref>

{{cquote|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.|4=Todd Caldecott|5=<ref name="preservative_compounds"/>}}

== See also ==

* [[Extract]]

== References ==
{{reflist}}

== External links ==
*[http://www.denvernaturopathic.com/news/GSE.html Grapefruit seed extract may owe its antimicrobial action to toxic chemical additives.]
*[http://www.wellvet.com/grapefruitseedextracts.html WellVet Company — Grapefruit Seed Extract: Articles, Conclusions, and References.]
*[http://www.spectroscopynow.com/coi/cda/detail.cda?chId=4&id=13654&type=Feature&page=1 Ecofriendly Pesticides Are Not What They Seem — Article by Steve Down; June 1, 2006.]

[[Category:Antioxidants]]
[[Category:Dietary supplements]]
[[Category:Grapefruit]]

[[fa:عصاره هسته دارابی]]
[[fr:Extrait de pépin de pamplemousse]]

Revision as of 16:35, 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]

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]

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.[25][26] Analysis shows the constituents of the seed extract and pulp are flavonoids,[27][28] ascorbic acid (commonly known as vitamin C[29][30][31]), tocopherols, citric acid,[25] limonoids,[32][33][34] sterols, and minerals.[35] A study suggests the consumption of the bioactive compounds found in grapefruit seed and pulp may help suppress the development of colon cancer.[36] Another study showed the flavonoid naringin is an excellent plasma lipid lowering and plasma antioxidant active elevating flavonone.[37]

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,[38] including warfarin (coumadin).[39] Grapefruit has components that inhibit the CYP3A4 enzyme in the intestine.[38] Thus, it is this effect that increases the rate of absorption of several drugs.[40] 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][41][42] 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][21][39]

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 i j k l von Woedtke T, Schlüter B, Pflegel P, Lindequist U, Jülich WD (1999). "Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained". Pharmazie. 54 (6): 452–6. PMID 10399191. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  2. ^ a b c d e f g 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 d e f Takeoka GR, Dao LT, Wong RY, Harden LA (2005). "Identification of benzalkonium chloride in commercial grapefruit seed extracts". J. Agric. Food Chem. 53 (19): 7630–6. doi:10.1021/jf0514064. PMID 16159196. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  7. ^ a b c d e f Todd Caldecott. Grapefruit seed extract antibiotic activity is due to preservative compounds. Townsend Letter for Doctors and Patients. 2005.
  8. ^ a b c Avula B, Dentali S, Khan IA (2007). "Simultaneous identification and quantification by liquid chromatography of benzethonium chloride, methyl paraben and triclosan in commercial products labeled as grapefruit seed extract". Pharmazie. 62 (8): 593–6. PMID 17867553. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  9. ^ a b c d Sugimoto N, Tada A, Kuroyanagi M; et al. (2008). "[Survey of synthetic disinfectants in grapefruit seed extract and its compounded products]". Shokuhin Eiseigaku Zasshi (in Japanese). 49 (1): 56–62. doi:10.3358/shokueishi.49.56. PMID 18344660. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  10. ^ a b c d Bekiroglu S, Myrberg O, Ostman K; et al. (2008). "Validation of a quantitative NMR method for suspected counterfeit products exemplified on determination of benzethonium chloride in grapefruit seed extracts". J Pharm Biomed Anal. 47 (4–5): 958–61. doi:10.1016/j.jpba.2008.03.021. PMID 18456447. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  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 Sakamoto S, Sato K, Maitani T, Yamada T (1996). "[Analysis of components in natural food additive "grapefruit seed extract" by HPLC and LC/MS]". Eisei Shikenjo Hokoku (in Japanese) (114): 38–42. PMID 9037863.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  22. ^ Chiambaretta F, Pouliquen P, Rigal D (1997). "[Allergy and preservatives. Apropos of 3 cases of allergy to benzalkonium chloride]". J Fr Ophtalmol (in French). 20 (1): 8–16. PMID 9099278.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  23. ^ Liu H, Routley I, Teichmann KD (2001). "Toxic endothelial cell destruction from intraocular benzalkonium chloride". J Cataract Refract Surg. 27 (11): 1746–50. doi:10.1016/S0886-3350(01)01067-7. PMID 11709246. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  24. ^ Eleraky NZ, Potgieter LN, Kennedy MA (2002). "Virucidal efficacy of four new disinfectants". J Am Anim Hosp Assoc. 38 (3): 231–4. PMID 12022408.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  25. ^ 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)
  26. ^ 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)
  27. ^ Drewnowski A, Gomez-Carneors C (2000). "Bitter taste, phytonutrients, and consumer: a review". Am. J. Clin. Nutr. 72 (6): 1424–35. PMID 11101467.
  28. ^ Tirillini B (2000). "Grapefruit: the last decade acquisitions". Fitoterapia. 71: 29–37. doi:10.1016/S0367-326X(00)00176-3. PMID 10930710.
  29. ^ 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.
  30. ^ Vitamin C. American Cancer Society. 2009.
  31. ^ The World's Healthiest Foods; Grapefruit. The George Mateljan Foundation. 2009.
  32. ^ 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)
  33. ^ 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)
  34. ^ 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.
  35. ^ 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)
  36. ^ 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)
  37. ^ 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)
  38. ^ a b Bakalar, Nicholas. Experts Reveal the Secret Powers of Grapefruit Juice. The New York Times. March 21, 2006.
  39. ^ 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)
  40. ^ 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)
  41. ^ Sharamon, S., Baginski, B.J. The Healing Power of Grapefruit Seed. Lotus Press, Wisconsin. 1996. ISBN 0-914955-27-6
  42. ^ Allan Sachs (1997). The authoritative guide to grapefruit seed extract. Mendocino, CA: LifeRhythm. ISBN 0-940795-17-5.
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