I am not a fan of grapefruit seed extract, because as a natural antibiotic it is a scam, a drug basically. But grapefruit seeds themselves do have antimicrobial effects and apparently, like many herbs, can reverse antibiotic resistance.
First the extract: Chemical manufacturers take leftover grapefruit pulp, a waste by-product from grapefruit juice production, and in an intensive, multi-step industrial chemical process, change the natural phenolic compounds into synthetic quaternary ammonium compounds. Typically, in chemical synthesis of this type, chemical reagents and catalysts are used under extreme high heat and pressure or vacuum. Synthetic ammonium chloride is one of the chemical catalysts used in this process. The products either contained the preserving substances benzethonium chloride, triclosan and methyl paraben or they didn’t work. GSE is not an essential oil, tincture or glycerite. Wikipedia’s article gives a significant discussion with sources on why you shouldn’t consider GSE a natural product.
However grapefruit or pomelo seeds themselves are potentially botanically useful antimicrobial agents.
This is not a widespread traditional herbal use. According to Todd Caldecott, Registered Herbalist (AHG) “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.” However the seeds of Citrus paradisi are reputed for the local management of array of human diseases including, anemia, diabetes mellitus and obesity by some Yoruba herbalists in Southwest, Nigeria.
It is possible to find new uses for plant constituents- indeed the pharmaceutical and supplement companies are working overtime to find uses. Ginkgo leaf was not used traditionally, at least to a significant extent, but the standardized extract has been found useful as a cerebral circulatory stimulant. But we may need to look at potential toxicity issues with herbs that lack significant traditional uses.
In the research based upon the Yoruba uses of the seeds, an alcoholic decoction of the seeds was fed to diabetic Wistar rats. It gave results comparable to Metformin, the control, in lowered triglycerides, fasting blood glucose, total cholesterol, LDL, VLDL and a rise in HDL.
Research on grapefruit seed tends to involve the adulterated grapefruit seed extract rather than the seeds themselves and I have found questionable sources of actions and constituents. For instance one study looks at the effects of essential oils and Citricidal, a brand name for GSE on MRSA. The commercial extract was effective, as it appears to be for a number of conditions including MRSA, parrot’s chlamydia, feline distemper (contraversial), Bordetella and various skin conditions. So although I consider GSE a synthetic drug of combined natural and synthetic origin, there is at least the possibility that there are useful products in the seeds or common herbal preparations thereof.
According to Duke’s Phytochemical Data Base the seeds have been tested to contain at least some concentration of these compounds with known activities below, although this only lists constituents for which there is research on the seed. The database does not indicate whether there is enough of the constituent to have a given overall effect, For instance, oxalic acid can be fatal, but not in this concentration. The recent diabetes study not cited by Duke, using a methanolic decoction of the seeds found the presence of alkaloids, flavonoids, cardiac glycosides, tannins and saponins in varying concentrations. Other constituents like the essential oil and fats are not listed below, probably because they have not been tested for this part of the plant:
OBACUNONE (Anticataleptic; Antifeedant; Pesticide)
OXALIC ACID (Acaricide; Antiseptic; CNS-Paralytic; Hemostatic; Irritant; Pesticide; Renotoxic; Varroacide)
PANTOTHENIC-ACID (Antiallergic; Antiarthritic; Anticephalagic; Anticlaudificant?; Antidermatitic; Antifatigue; Antihypercholesterolemic; Antiielus? ; Antiinsomniac?; Antirheumatitic? ; Cancer-Preventive)
LIMONIN (Anticataleptic; Antifeedant; Antileukemic; Antimalarial; Pesticide)
NARINGIN (Aldose-Reductase-Inhibito; Antidermatitic; Antiinflammatory; Antimutagenic; Antineuropathic; Antioxidant; Antiviral; Cancer-Preventive; FLavor; Myorelaxant; Oviposition-Stimulant; Pesticide)
The essential oil of grapefruit seed is sold as being antibacterial, antifungal, antiviral and astringent although direct research is difficult to find on the essential oil. There is research showing that the furanocoumarins in the essential oil my inhibit cytochrome P450 which interferes with liver detoxification. A shampoo made from constituents of the grapefruit (part not specified) has been tested to kill lice.
The number of insecticidal and parasiticidal compounds in the constituents indicates to me that grapefruit seeds are likely a short term herb, useful for acute infections and parasite conditions. It is meaningful to me that while grapefruit and similar citrus like pomelo are found all over the world, the seeds are only consumed in tropical regions of Africa where their ability to clear excess parasites might justify exposure to low levels of potential toxins. The rat study was not long term, and wasn’t done on humans.
Nonetheless there may be potential for short term use or for longer term use of a modified natural compound. The small (4 person) study below is a human study, where consuming 5-6 seeds every four hours had a demonstrated effect in treating UTIs.
1: J Altern Complement Med. 2005 Apr;11(2):369-71. PMID: 15865506
Three middle-aged males and one female were diagnosed as having urinary tract infections (UTIs) between 2001 and 2003 in the Wesley Guild Hospital, Ilesa, a unit of Obafemi Awolowo University Teaching Hospitals Complex, Ile Ife, Osun State, Nigeria. Of the 4 patients, only the female was asymptomatic. The 3 males had Pseudomonas aeruginosa, Klebsiella species, and Staphylococcus aureus, respectively, in their urine samples, while the female had Escherichia coli. All 4 patients were treated with grapefruit seeds (Citrus paradisi) orally for 2 weeks and they all responded satisfactorily to the treatment except the man with P. aeruginosa isolate. However, the initial profuse growth of Pseudomonas isolate in the patient that was resistant to gentamicin, tarivid, and augmentin later subsided to mild growth with reversal of the antibiotic resistance pattern after 2 weeks’ treatment with grapefruit seeds. These preliminary data thus suggest an antibacterial characteristic of dried or fresh grapefruit seeds (C. paradisi) when taken at a dosage of 5 to 6 seeds every 8 hours, that is comparable to that of proven antibacterial drugs.
Oyelami OA, Agbakwuru EA, Adeyemi LA, Adedeji GB. The effectiveness of grapefruit (Citrus paradisi) seeds in treating urinary tract infections. J Altern Complement Med. 2005 Apr;11(2):369-71.
Takeoka G, Dao L, Wong RY, Lundin R, Mahoney N (July 2001). “Identification of benzethonium chloride in commercial grapefruit seed extracts”. J. Agric. Food Chem. 49 (7): 3316–20. doi:10.1021/jf010222w. PMID 11453769
Edwards-Jones V, Buck R, Shawcross SG, Dawson MM, Dunn K.The effect of essential oils on methicillin-resistant Staphylococcus aureus using a dressing model. Burns. 2004 Dec;30(8):772-7.PMID: 15555788
Warnke PH, Becker ST, Podschun R, Sivananthan S, Springer IN, Russo PA, Wiltfang J, Fickenscher H, Sherry E.The battle against multi-resistant strains: Renaissance of antimicrobial essential oils as a promising force to fight hospital-acquired infections.J Craniomaxillofac Surg. 2009 Oct;37(7):392-7. Epub 2009 May 26.PMID: 19473851
Adeneye AA.Hypoglycemic and hypolipidemic effects of methanol seed extract of Citrus paradisi Macfad (Rutaceae) in alloxan-induced diabetic Wistar rats. Nig Q J Hosp Med. 2008 Oct-Dec;18(4):211-5.PMID: 19391322
Abdel-Ghaffar F, Semmler M, Al-Rasheid K, Klimpel S, Mehlhorn H.
Efficacy of a grapefruit extract on head lice: a clinical trial. Parasitol Res. 2010 Jan;106(2):445-9. Epub 2009 Nov 27.PMID: 19943066
Todd Caldecott. Grapefruit Seed Extract. Medical Herbalism. 2005:14(3);1
GreenMedicineInfo Grapefruit seed extract is effect in treating urinary tract infections.
Photo Credit: Sprouting grapefruit seed. Wonders of Nature, The Grapefruit Tree Has Been Born http://myonlyphoto.blogspot.com/2009/05/wonders-of-nature-grapefruit-tree-has.html