Grapefruit Seed Extract a big mistake?

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Pharmazie. 1999 Jun;54(6):452-6.

Aspects of the antimicrobial efficacy of grapefruit seed extract and its

relation to preservative substances contained.

von Woedtke T, Schluter B, Pflegel P, Lindequist U, Julich WD.

Institute of Pharmacy, Ernst Moritz Arndt University, Greifswald, Germany.

The antimicrobial efficacy as well as the content of preservative agents of

six commercially available grapefruit seed extracts were examined. Five of

the six extracts showed a high growth inhibiting activity against the test

germs Bacillus subtilis SBUG 14, Micrococcus flavus SBUG 16, Staphylococcus

aureus SBUG 11, Serratia marcescens SBUG 9, Escherichia coli SBUG 17,

Proteus mirabilis SBUG 47, and Candida maltosa SBUG 700. In all of the

antimicrobial active grapefruit seed extracts, the preservative

benzethonium chloride was detected by thin layer chromatography.

Additionally, three extracts contained the preserving substances triclosan

and methyl parabene. In only one of the grapefruit seed extracts tested no

preservative agent was found. However, with this extract as well as with

several self-made extracts from seed and juiceless pulp of grapefruits

(Citrus paradisi) no antimicrobial activity could be detected (standard

serial broth dilution assay, agar diffusion test). Thus, it is concluded

that the potent as well as nearly universal antimicrobial activity being

attributed to grapefruit seed extract is merely due to the synthetic

preservative agents contained within. Natural products with antimicrobial

activity do not appear to be present.

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