- Grapefruit seed extract
Grapefruit seed extract (GSE), also known as citrus seed extract, is a liquid derived from the seeds, pulp, and white membranes of grapefruit. 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. Commercially available GSE sold to consumers are made from the seed, pulp, glycerin, and synthetic preservatives all blended together. Grapefruit seed extract is sold as a food supplement and used in cosmetics because it is a claimed natural antimicrobial.
An early proponent was Dr. Jacob Harich (1919–1996). A long time promoter of GSE was Aubrey Hampton, the founder of Aubrey Organics. Some marketers of GSE affirm this extract to be a safe, natural, and an effective preservative. This extract has been stated by some practitioners of alternative medicine to possess antibacterial, antiviral, and antifungal properties. It has been recommended by some nutritionists for the treatment of candidiasis, earache, throat infections, and diarrhea. GSE is promoted at health food shops and on the internet.
There are conflicting scientific demonstrations of the efficacy of GSE. Suspicions about the true nature of the active compounds in GSEs arose when synthetic additives were found in commercial products. Suspected counterfeit grapefruit seed extracts were adulterated with synthetic preservatives. When preservatives were not present in some of the extracts, laboratory tests found the natural extracts had no natural antimicrobial attributes of their own. 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.
The grapefruit is a subtropical citrus tree grown for its fruit which was originally named the "forbidden fruit" of Barbados. The fruit was first documented in 1750 by Rev. Griffith Hughes describing specimens from Barbados. All parts of the fruit have uses. The fruit is mainly consumed for a tangy juice. The peel is expressed into an aromatherapy oil and is also a source of dietary fiber. The seed and pulp as a by-product of the juice industry is sold as cattle feed and is manufactured for use to make an extract. 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. Aubrey Hampton, founder of Aubrey Organics, has promoted citrus seed extract, a component in "Aubrey’s Preservative", for more than 25 years. Today, GSE is mostly promoted at health food shops and on the internet.
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. The preliminary studies for the antimicrobial effect state that the Citricidal commercial brand of GSE was used for testing. 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. 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. 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. It is inconceivable that the preservative benzethonium chloride is formed during any extraction and/or processing of grapefruit seeds and pulp. 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. Another in vitro study claimed GSE had antibacterial properties. As with the branded in vitro test this extract was contaminated. The ethanolic grapefruit seed and pulp extract tested was prepared or contaminated with ethanol, a chemical solvent used in the extraction process. Ethanol, also known as ethyl alcohol, is effective in inhibiting bacteria. 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 concluded self-made pure GSE has no natural antimicrobial properties and commercial GSE has been identified with contamination from synthetic preservatives.
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. Some samples were shown to contain up to 22% benzalkonium chloride by weight, despite the known allergenicity and toxicity of the compound at higher doses. 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. Although citrus seed extract is sold in health food markets, there is no good evidence for any natural antimicrobial activity.
A study that examined the antiviral properties of GSE found that GSE had no efficacy as a disinfectant for feline calicivirus and feline parvovirus. 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. Newer studies found many commercial grapefruit seed extracts contaminated with synthetic preservatives. In a 2007 study the main synthetic antimicrobial agent identified in commercial GSE samples was benzethonium chloride. In a 2008 study synthetic disinfectants such as benzethonium or benzalkonium chloride were identified in most of the commercial GSE products. In a 2008 study suspected counterfeit products were determined to contain benzethonium chloride in grapefruit seed extract samples.
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. Various analytical methods were developed to determine the constituents or compounds in GSE samples which include particle-induced x-ray emission (PIXE), electrospray ionization mass spectrometry (ESI-MS), high performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), and nuclear magnetic resonance (NMR) analysis.
There is evidence that the extract of citrus grapefruit seed has antioxidant properties. Analysis shows the constituents of the seed extract and pulp are flavonoids, ascorbic acid (commonly known as vitamin C), tocopherols, citric acid, limonoids, sterols, and minerals. A study suggests the consumption of the bioactive compounds found in grapefruit seed and pulp may help suppress the development of colon cancer. Another study showed the flavonoid naringin is an excellent plasma lipid lowering and plasma antioxidant active elevating flavonone.
Self-made pure GSE processed without solvents is prepared by grinding the grapefruit seed and juiceless pulp, then mixing with glycerin.
Commercially available GSE sold to consumers are made from the seed, pulp, glycerin, and synthetic preservatives all blended together.
Grapefruit can have a number of interactions with certain drugs, increasing the potency of many compounds, including warfarin (coumadin). Grapefruit has components that inhibit the CYP3A4 enzyme in the intestine. Thus, it is this effect that increases the rate of absorption of several drugs. There are concerns about the safety of ingesting synthetic preservatives found in grapefruit seed extract.
GSE usage has been popularized by many companies within the scope of the health food industry. There are books exclusively dedicated to GSE. This extract is promoted by marketers on the internet and some health food stores recommend its use. 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.
“ 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, 
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