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Plant Part Used

Seed and pulp extract.

Active Constituents

Diphenol hydroxybenzene complex (triclosan),(1)mono and sesquiterpenes(9),polymethoxyflavones, nobiletin, heptamethoxyflavone and tangeretin(10),imonoids and naringin, (11) phenolic acids. (12)[span class=alert]

This section is a list of chemical entities identified in this dietary supplement to possess pharmacological activity. This list does not imply that other, yet unidentified, constituents do not influence the pharmacological activity of this dietary supplement nor does it imply that any one constituent possesses greater influence on the overall pharmacological effect of this dietary supplement.[/span]


Uses of grapefruit seed extract in various industries include: agriculture (bactericide in both pre-harvest and post-harvest treatment); fish and poultry industry (disinfectant for fresh fish and poultry); also preservative for these processed foods; animal feed industry (mold inhibitor and antiparasitic); food industry (preservative and antioxidant); cosmetic industry (preservative and antimicrobial); water treatment (disinfectant for contaminated water); as a disinfectant in hospitals and healthcare facilities; and in the dietary supplement industry (as antifungal, antibacterial, helps restore bowel health).

Dosage Info

Dosage Range

100mg, 1-3 times a day with meals.

Liquid: 5-10 drops, 2-3 times a day with meals.

Oral rinse: 5-10 drops in water, 2-3 times a day, swish and expectorate.

Most Common Dosage

100mg, 3 times a day with meals.

Liquid: 5 drops, 3 times a day with meals.

Oral rinse: 5 drops in water, 3 times a day, swish and expectorate.


[span class=doc]Standardization represents the complete body of information and controls that serve to enhance the batch to batch consistency of a botanical product, including but not limited to the presence of a marker compound at a defined level or within a defined range.[/span]

Not applicable.


Frequently Reported Uses

  • Antiviral.
  • Disinfectant
Other Reported Uses
  • Antibacterial
  • Antifungal
  • Antiparasitic

Toxicities & Precautions


Grapefruit seed extract is safe in recommended dosages.


If allergy develops, discontinue use.

Side Effects

If diarrhea develops, discontinue use.

Pregnancy/ Breast Feeding

Use in pregnancy has not yet been determined.


Grapefruit seed extract has been reported to be a broad-spectrum antimicrobial both in vitro and in vivo. Studies indicate that the antimicrobial activity of grapefruit seed extract exists in the cytoplasmic membrane of the invading bacteria, where the uptake of amino acids is prevented. There is disorganization of the cytoplasmic membrane and leakage of low molecular weight cellular contents, ultimately resulting in inhibition of cellular respiration and death. (2)

Grapefruit seed extract also inhibits the growth of H. pylori and C. jejuni, both causative agents in gastrointestinal ulcers. (3) Not only does grapefruit seed extract aid in decreasing gastrointestinal ulceration, it also inhibits Candida overgrowth, which is a major concern in bowel health and maintaining normal bacterial flora of the GIT. (4) In one human study in individuals with gastrointestinal permeability due to bowel flora imbalance, an improvement in constipation, flatulence, abdominal distress, and night rest were noticed after four weeks of therapy. Most clinicians now agree on the importance of maintaining homeostasis of the microflora in health and disease. (5)

A recent study was performed to determine the antimicrobial efficacy as well as the content of preservative agents of six commercially available grapefruit seed extracts in Europe. (6) Synthetic preservative agents were found to be contained within the effective products. The product with no synthetic preservative did not appear to have any antimicrobial activity.

The polymethoxyflavones content in grapefruit seed extract was reported to be effective as an antifungal against Penicillium digitatum. (10)

Grapefruit seed extract is not reported to contain naringin, the constituent in grapefruit juice that may alter the metabolism of certain medications. (7) However, until further research is performed, use grapefruit seed extract with caution in individuals on medications metabolized by the CYP34A pathway, including terfenadine, astemizole, cisapride, “statin" hypocholesterolemics, saquinavir, cyclosporin, midazolam, triazolam, verapamil, and warfarin among others. (8)


  1. Unpublished literature. BioChem Research. Lakeport, CA. 1994.
  2. Ionescu G, et al. Oral Citrus seed extract. J Orthomolecula Med. 1990;5(3):72-74.
  3. View Abstract: Arimi SM. Campylobacter infection in humans.East Afr Med J. Dec1989;66(12):851-5.
  4. Ionescu G, et al. Oral Citrus seed extract. J Orthomolecula Med. 1990;5(3):72-74.
  5. View Abstract: Fitzgerald JF. Colonization of the gastrointestinal tract. Mead Johnson Symp Perinat Dev Med. 1977;(11):35-8.
  6. View Abstract: Von Woedtke T, Schluter B, Pflegel P, et al. Aspects of the Antimicrobial Efficacy of Grapefruit Seed Extract and Its Relation to Preservative Substances Contained. Pharmazie. Jun1999;54(6):452-6.
  7. View Abstract: Bailey DG, et al. Grapefruit juice-drug interactions.Br J Clin Pharmacol. Aug1998;46(2):101-10.
  8. View Abstract: Martin J, Krum H. Cytochrome P450 drug interactions within the HMG-CoA reductase inhibitor class: are they clinically relevant? Drug Saf. 2003;26(1):13-21.
  9. F. Guido, L.C Pier. Odour gradients and patterns in volatile emission of different plant parts and developing fruits of grapefruit (Citrus paradisi L.). Food Chemistry, Volume 120, Issue 4, 15 June 2010, Pages 984-992
  10. A. Ortuño, A. Báidez, P. Gómez, M.C. Arcas, I. Porras, A. García-Lidón, J.A. Del Río. Citrus paradisi and Citrus sinensis flavonoids: Their influence in the defence mechanism against Penicillium digitatum. Food Chemistry, Volume 98, Issue 2, 2006, Pages 351-358
  11. Y. Jun, V.D Deepak, T.T Romeo, K.S Rakesh, S.P Bhimanagouda. Supercritical fluid extraction of limonoids and naringin from grapefruit (Citrus paradisi Macf.) seeds. Food Chemistry, Volume 105, Issue 3, 2007, Pages 1026-1031
  12. X. Guihua, Y. Xingqian, L. Donghong, M. Yaqin, C. Jianchu. Composition and distribution of phenolic acids in Ponkan (Citrus poonensis Hort. ex Tanaka) and Huyou (Citrus paradisi Macf. Changshanhuyou) during maturity. Journal of Food Composition and Analysis, Volume 21, Issue 5, August 2008, Pages 382-389

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