GRAPEFRUIT SEED EXTRACT (GSE): Let the buyer beware

Grapefruit seed extract (GSE), sometimes referred to as citrus seed extract or Citricidal [INCI name: Citrus grandis (grapefruit) seed extract], is promoted and used as a natural broad-spectrum, but non-toxic, antimicrobial and preservative. It is used in a wide range of ‘natural’ cosmetics as a preservative, and in personal care products because of its claimed bactericide, fungicide, antiviral, and anti-parasitic action.

However, much of the GSE on the market is not a simple extract (as the name would imply), but in fact is a highly processed and chemically modified product. Indeed a lot of controversy surrounds the use of GSE, both in terms of how natural it is and also how effective it is. A substantial number of overseas studies have reported it to be adulterated with the synthetic quaternary ammonium anti-bacterials benzethonium chloride and benzalkonium chloride (see


In 2007 I purchased five samples of GSE from NZ shops or from internet suppliers and analysed them for the presence of benzethonium chloride or benzalkonium chloride.   The sample extraction and analysis was based on that of Takeoka et al. (2001).

By thin layer chromatography (TLC) and high pressure liquid chromatography/mass spectrometry (HPLC/MS) four of the five samples contained benzethonium chloride, the remaining sample contained benzalkonium chloride.

HPLC/MS of one typical sample showing the presence of benzethonium chloride.

These results are consistent with the numerous overseas findings that GSE is adulterated with synthetic quaternary ammonium compounds.  A sample of Citricidal I obtained directly from the American manufacturer tested positive for benzethonium chloride.  It essentially was benzethonium chloride dissolved in glycerin. Many companies sell this product under their own label which explains why so many ‘different’ grapefruit seed extracts contain exactly the same adulterant. 

As grapefruit seed extract is frequently used as a ‘natural preservative’ in cosmetics I also tested a popular natural NZ cosmetic lotion that had grapefruit seed extract as a declared ingredient. The lotion tested positive for benzethonium chloride.  A great many cosmetic products that claim on their label to be free of synthetic preservatives are not as they use GSE as part of their preservative system.  

Points to note:
1)    Benzethonium chloride and benzalkonium chloride do not exist naturally in grapefruit seeds, or in a truly natural extract of grapefruit seeds.

2)    It is not plausible that the benzethonium chloride or benzalkonium chloride could be formed during the manufacturing process in the high concentrations found in commercial GSE.  The logical conclusion is that they are added.  

3)   The manufacturers of Citricidal have claimed that the researchers that have identified benzethonium chloride in their product are mistaken.  If you believe that multiple independent universities using a variety of sophisticated analyses can all be wrong, and all mistakenly identify exactly the same chemical, then I have a bridge in Brooklyn I can sell you :)  

4)    The Material Safety Data Sheet (MSDS) for Citricidal lists it as “Diphenol hydroxybenzene”. This is completely misleading (and a potential safety hazard) as neither benzethonium chloride nor benzalkonium chloride can be described this way. Neither is it an accurate or informative description of the components of grapefruit seed.     

5)    In addition, people with chemistry training will recognise that the description "diphenol hydroxybenzene" is not the correct way to name a chemical compound. 'Hydroxybenzene' is a benzene ring with a hydroxy group attached, 'phenol' is also a benzene ring with a hydroxy group attached.   So "diphenol hydroxybenzene" just loosely says that we have some benzene rings with hydroxy groups stuck on them somewhere!  All a completely untrue description of GSE. How this can be acceptable on an MSDS sheet, and can get through Customs, beats me.     

6)   The numerous studies that have found GSE to be effective as an antimicrobial or preservative are impossible to interpret given the high level of adulteration of commercial GSE. Given that truly natural extracts of grapefruit seed have been found to have much lower antimicrobial activity it would appear that the effectiveness reported for commercial GSE is due predominantly to the synthetic quaternary ammonium compounds in the product.  

7)    Producers of ‘natural’ GSE warn consumers to keep the product out of the eyes. Quaternary ammonium compounds (such as benzethonium chloride) are particularly harmful to the eyes.

The public have a right to informed consent when using a health product.  In particular, people should not be lead to believe that a product is natural when, in fact, it contains synthetic chemicals. If you are purchasing a product that contains GSE ask if it has been independently tested for the presence of benzethonium chloride or benzalkonium chloride.  If not then it would be unwise to trust the product – let the buyer beware.

Dr Steve Humphries
Hebe Botanicals Ltd

Copyright Hebe Botanicals Ltd 2008

Takeoka, G.R., Dao, L.T., Rosalind, Y., Wong, R..Y., Lundin, R., & Mahoney, N. (2001). Identification of benzethonium chloride in commercial grapefruit seed extracts. Journal of Agriculture and Food Chemistry, 49, 3316-3320.