encyclopedia

Grapefruit Seed Extract and Oil

Natural Sources:     

Grapefruit     

Forms:     

Grapefruit juice; grapefruit extracts; and grapefruit oil extract for cosmetics.     

Therapeutic Uses:     

– Antibacterial (seed extract and oil in cosmetics)
– Antifungal (seed extract and oil in cosmetics)
– Anti-inflammatory
– Antimicrobial (seed extract and oil in cosmetics)
– Antioxidant
– Antiviral (seed extract)
– Astringent
– Cancer Prevention
– Cellular Regeneration
– Cholesterol Lowering
– Cleansing
– Detoxification
– Heart Health Maintenance
– High Cholesterol
– Inflammation
– Lupus nephritis
– Parasites (seed extract)
– Preservative (seed extract and oil used in cosmetics)
– Rheumatoid Arthritis
– Weight Loss     

Overview:     

Grapefruit, Citrus paradisi Macfad. [Fam. Rutaceae] is native to Jamaica but is largely cultivated in the United States. The skins of grapefruit may be yellow or pinkish and the pulp of the fruit may be yellow, pinkish, or reddish with a sharp, acidic, sweet taste and fragrance. Grapefruit is rich in vitamin C and potassium and is also a good source of folate, iron, calcium, and other minerals. The pink and red varieties are rich in beta-carotene, a precursor of vitamin A, and lycopene, an anticancer carotenoid also found in tomatoes and watermelon. Grapefruit stimulates the appetite and is used for its digestive, antiseptic, tonic, and diuretic qualities. The fruit provides a good source of dietary fiber, as it is high in fiber and low in calories making it an ideal food to include in a sensible weight-loss diet. Grapefruits are especially high in pectin, a soluble fiber that helps lower blood cholesterol. The fruit also contains many bioflavonoids and other plant chemicals that protect against cancer and heart disease. Pink and red grapefruits are high in lycopene, an antioxidant associated with reduced risk of prostate cancer. A 6-year Harvard study involving 48,000 doctors and other health professionals has linked 10 servings of lycopene-rich foods a week with a 50 percent reduction in prostate cancer.
Other protective plant chemicals found in grapefruits include phenolic acid, which inhibits the formation of cancer-causing nitrosamines; limonoids, terpenes, and monoterpenes, which induce the production of enzymes that help prevent cancer; and bioflavonoids, which inhibit the action of hormones that promote tumor growth. Some people with rheumatoid arthritis, lupus nephritis, and other inflammatory disorders report that eating grapefruit daily seems to alleviate their symptoms, attributed to compounds that block inflammatory prostaglandins. Grapefruit oil and seed extracts are also used in cosmetic formulations as natural preservatives.

Grapefruit Seed Extract as an Excellent Preservative:

Non-published studies and testimonials report grapefruit-seed extract to be effective against more than 800 bacterial and viral strains, 100 strains of fungus, and a large number of single and multicelled parasites. A recent scientific study investigated grapefruit-seed extract for antibacterial activity at varying time intervals and concentration levels and tissue toxicity at varying concentrations in an effort to determine if a concentration existed that was both microbicidal and nontoxic and in what period of time. The tests indicated that from the 1:1 through the 1:128 concentrations, grapefruit-seed extract remained toxic as well as bactericidal. However, test results indicated that at the 1:512 dilution, grapefruit-seed extract remained bactericidal, but completely nontoxic. The initial data shows grapefruit-seed extract to have antimicrobial properties against a wide range of gram-negative and gram-positive bacteria at dilutions found to be safe. The mechanism of grapefruit-seed extract antibacterial activity was revealed using scanning electron microscopy. It was shown that grapefruit-seed extract disrupts the bacterial membrane and liberates the cytoplasmic contents within 15 minutes after contact even at more dilute concentrations.

Chemistry:     

Grapefruit pulp contains significant levels of vitamin C; potassium, folate, calcium, and iron. The pink and red varieties also contain beta-carotene and lycopene, antioxidants that the body can convert to vitamin A. Other protective plant chemicals found in grapefruits include phenolic acid, limonoids, terpenes, monoterpenes, D-glucaric acid and flavonoids including hesperetin and naringenin. Grapefruit oil contains: nonanal, nootkatone, beta-Pinene, alpha-phellandrene, 3-carene, ocimene, octanol, trans-linalool oxide, cis-p-mentha-2,8-dien-1-ol, alpha-pinene, limonene, linalool, citronellal, alpha-terpineol, neral, dodecanal, and alpha-humulene. Compounds that are toxic to the Caribbean fruit fly (alpha-pinene, limonene, alpha-terpineol, and some aldehydes) decrease with time in storage, thus suggesting grapefruit becomes increasingly susceptible to the fly during storage. The Nutrition Information for whole grapefruits (Nutritional information per 100 g) is as follows: Water, 91%; Protein, 0.6g; Fat, 0.1g; Carbohydrates, 8g; Fiber, 0.6g and calories, 30 to 33.     

Suggested Amount:     

Half a grapefruit provides more than 50 percent of the adult Recommended Dietary Allowance (RDA) of vitamin C; it also has 325mg of potassium, 25mcg (micrograms) of folate, 40mg of calcium, and l mg of iron. The pink and red varieties are high in beta-carotene, an antioxidant that the body converts to vitamin A. A cup of unsweetened grapefruit juice has 95mg of vitamin C, more than 150 percent of the RDA, and most of the other nutrients found in the fresh fruit. Grapefruit is an ideal food to include in a sensible weight-loss diet as a serving contains less than 100 calories and its high-fiber content satisfies hunger. Grapefruit oil and grapefruit seed extract are used in cream formulations as natural preservatives.     

Drug Interactions:     

Grapefruit has serious interactions with many commonly prescribed medications and can lead to unpredictable and hazardous levels of certain important drugs. Grapefruit juice inhibits a special enzyme in the intestines that is responsible for the natural breakdown and absorption of many medications and when the action of this enzyme is blocked, the blood levels of these medications increase, which can lead to toxic side effects from the medications. Grapefruit juice research suggests that flavonoids and furanocoumarins are responsible for this effect. The following medications (and possibly others) should not be consumed with grapefruit juice unless advised by a doctor: Statins (Cholesterol Lowering Drugs): Baycol (Cerivastatin); Mevacor (Lovastatin); Lipitor (Atorvastatin); Zocor (Simvastatin). Antihistamines: Ebastine; Seldane (Terfenadine, taken off the U.S. market). Calcium Channel Blockers (Blood Pressure Drugs): Nimotop (Nimodipine); Nitrendipine; Plendil (Felodipine); Pranidipine; Sular (Nisoldipine); Psychiatric Medications: Buspar (Buspirone); Halcion (Triazolam); Tegretol (Carbamazepine); Valium (Diazepam); Versed (Midazolam). Intestinal Medications: Propulsid (Cisapride, taken off the U.S. market). Immune Suppressants: Neoral (Cyclosporine); Prograf (Tacrolimus). Pain Medications: Methadone. Impotence Drug: Viagra (Sildenafil). Other drugs may have potential interactions with grapefruit including: Amiodarone (Cordarone-₯); Cilostazol (Pletal-₯); Donepezil (Aricept-₯); Losartan (Cozaar-₯); Montelukast (Singulair-₯); Pimozide (Orap-₯); Quetiapine (Seroquel-₯); Tamoxifen (Nolvadex-₯) and Tamsulosin (Flomax-₯).     

Contraindications:     

Grapefruits are contraindicated for people who are allergic to citrus fruits as they are likely to react to grapefruits as well. The sensitivity may be to the fruit itself or to oil in the peel.     

Side Effects:     

Toxic blood levels of many medications can occur when patients taking them consume grapefruit or grapefruit juice. The high blood levels of the medications can cause damage to organs or impair their normal function, which can be dangerous. Do not consume grapefruit or grapefruit juice while taking medications or consult with your doctor before doing so.     

References:     

Cerda JJ, Robbins FL, Burgin CW, Baumgartner TG, Rice RW. 1988. The effects of grapefruit pectin on patients at risk for coronary heart disease without altering diet or lifestyle. Clin Cardiol 1988 Sep; 11(9): 589-94.
 
Hakim IA, Harris RB, Ritenbaugh C. 2000. Citrus peel use is associated with reduced risk of squamous cell carcinoma of the skin. Nutr Cancer 2000; 37(2): 161-8.
 
Heggers JP, Cottingham J, Gusman J, Reagor L, McCoy L, Carino E, Cox R, Zhao JG, Reagor L. 2002. The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity. J Altern Complement Med 2002 Jun; 8(3): 333-40.
 
International Cyber Business Services, Inc. (ICBS) 2002. Holisticonline.com Grapefruit Monograph. http://www.holistic-online.com/Herbal-Med/_Herbs/h_grapefruit.htm.
 
So FV, Guthrie N, Chambers AF, Moussa M, Carroll KK. 1996. Inhibition of human breast cancer cell proliferation and delay of mammary tumorigenesis by flavonoids and citrus juices. Nutr Cancer 1996; 26(2): 167-81.
 
Sun J, Chu YF, Wu X, Liu RH. 2002. Antioxidant and antiproliferative activities of common fruits. J Agric Food Chem 2002 Dec 4; 50(25): 7449-54.

Additional Information:     

Grapefruit Research:
 
Cerda JJ, Robbins FL, Burgin CW, Baumgartner TG, Rice RW. 1988. The effects of grapefruit pectin on patients at risk for coronary heart disease without altering diet or lifestyle. Clin Cardiol 1988 Sep; 11(9): 589-94.
 
Department of Medicine, University of Florida College of Medicine, Gainesville 32610.
 
Dietary intake of cholesterol has been linked to coronary heart disease. The effect of grapefruit pectin (Citrus paradisi) on plasma cholesterol, triglycerides, very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and the low-density lipoprotein:high-density lipoprotein cholesterol ratio was studied. The study design was a 16-week double-blind, crossover (placebo or pectin) using 27 human volunteers screened to be at medium to high risk for coronary heart disease due to hypercholesterolemia. The study did not interfere with the subjects' current diet or lifestyle. Grapefruit pectin supplementation decreased plasma cholesterol 7.6%, low-density lipoprotein cholesterol 10.8%, and the low-density lipoprotein:high-density lipoprotein cholesterol ratio 9.8%. The other plasma lipid fractions studied showed no significant differences. We conclude that a grapefruit pectin-supplemented diet, without change in lifestyle, can significantly reduce plasma cholesterol.
 

Sun J, Chu YF, Wu X, Liu RH. 2002. Antioxidant and antiproliferative activities of common fruits. J Agric Food Chem 2002 Dec 4; 50(25): 7449-54.
 
Department of Food Science, Cornell University, Ithaca, New York 14853-7201, USA.
 
Consumption of fruits and vegetables has been associated with reduced risk of chronic diseases such as cardiovascular disease and cancer. Phytochemicals, especially phenolics, in fruits and vegetables are suggested to be the major bioactive compounds for the health benefits. However, the phenolic contents and their antioxidant activities in fruits and vegetables were underestimated in the literature, because bound phenolics were not included. This study was designed to investigate the profiles of total phenolics, including both soluble free and bound forms in common fruits, by applying solvent extraction, base digestion, and solid-phase extraction methods. Cranberry had the highest total phenolic content, followed by apple, red grape, strawberry, pineapple, banana, peach, lemon, orange, pear, and grapefruit. Total antioxidant activity was measured using the TOSC assay. Cranberry had the highest total antioxidant activity (177.0 +/- 4.3 micromol of vitamin C equiv/g of fruit), followed by apple, red grape, strawberry, peach, lemon, pear, banana, orange, grapefruit, and pineapple. Antiproliferation activities were also studied in vitro using HepG(2) human liver-cancer cells, and cranberry showed the highest inhibitory effect with an EC(50) of 14.5 +/- 0.5 mg/mL, followed by lemon, apple, strawberry, red grape, banana, grapefruit, and peach. A bioactivity index (BI) for dietary cancer prevention is proposed to provide a new alternative biomarker for future epidemiological studies in dietary cancer prevention and health promotion.
 

So FV, Guthrie N, Chambers AF, Moussa M, Carroll KK. 1996. Inhibition of human breast cancer cell proliferation and delay of mammary tumorigenesis by flavonoids and citrus juices. Nutr Cancer 1996; 26(2): 167-81.
 
Department of Pharmacology and Toxicology, University of Western Ontario, London, Canada.
 
Two citrus flavonoids, hesperetin and naringenin, found in oranges and grapefruit, respectively, and four noncitrus flavonoids, baicalein, galangin, genistein, and quercetin, were tested singly and in one-to-one combinations for their effects on proliferation and growth of a human breast carcinoma cell line, MDA-MB-435. The concentration at which cell proliferation was inhibited by 50% (IC50), based on incorporation of [3H]thymidine, varied from 5.9 to 140 micrograms/ml for the single flavonoids, with the most potent being baicalein. IC50 values for the one-to-one combinations ranged from 4.7 micrograms/ml (quercetin + hesperetin, quercetin + naringenin) to 22.5 micrograms/ml (naringenin + hesperetin). All the flavonoids showed low cytotoxicity (> 500 micrograms/ml for 50% cell death). Naringenin is present in grapefruit mainly as its glycosylated form, naringin. These compounds, as well as grapefruit and orange juice concentrates, were tested for their ability to inhibit development of mammary tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) in female Sprague-Dawley rats. Two experiments were conducted in which groups of 21 rats were fed a semipurified diet containing 5% corn oil and were given a 5-mg dose of DMBA intragastrically at approximately 50 days of age while in diestrus. One week later, individual groups were given double-strength grapefruit juice or orange juice or fed naringin or naringenin at levels comparable to that provided by the grapefruit juice; in the second experiment, the rats were fed a semipurified diet containing 20% corn oil at that time. As expected, rats fed the high-fat diet developed more tumors than rats fed the low-fat diet, but in both experiments tumor development was delayed in the groups given orange juice or fed the naringin-supplemented diet compared with the other three groups. Although tumor incidence and tumor burden (grams of tumor/rat) were somewhat variable in the different groups, rats given orange juice had a smaller tumor burden than controls, although they grew better than any of the other groups. These experiments provide evidence of anticancer properties of orange juice and indicate that citrus flavonoids are effective inhibitors of human breast cancer cell proliferation in vitro, especially when paired with quercetin, which is widely distributed in other foods.
 

Hakim IA, Harris RB, Ritenbaugh C. 2000. Citrus peel use is associated with reduced risk of squamous cell carcinoma of the skin. Nutr Cancer 2000; 37(2): 161-8.

Cancer Prevention and Control, Arizona Cancer Center, College of Medicine, University of Arizona, Tucson, AZ 85724, USA. ihakim@azcc.arizona.edu
 
Limonene has demonstrated efficacy in preclinical models of breast and colon cancers. The principal sources of d-limonene are the oils of orange, grapefruit, and lemon. The present case-control study was designed to determine the usual citrus consumption patterns of an older Southwestern population and to then evaluate how this citrus consumption varied with history of squamous cell carcinoma (SCC) of the skin. In this Arizona population, 64.3% and 74.5% of the respondents reported weekly consumption of citrus fruits and citrus juices, respectively. Orange juice (78.5%), orange (74.3%), and grapefruit (65.3%) were the predominant varieties of citrus consumed. Peel consumption was not uncommon, with 34.7% of all subjects reporting citrus peel use. We found no association between the overall consumption of citrus fruits [odds ratio (OR) = 0.99, 95% confidence interval (CI) = 0.73-1.32] or citrus juices (OR = 0.97, 95% CI = 0.71-1.31) and skin SCC. However, the most striking feature was the protection purported by citrus peel consumption (OR = 0.66, 95% CI = 0.45-0.95). Moreover, there was a dose-response relationship between higher citrus peel in the diet and degree of risk lowering. This is the first study to explore the relationship between citrus peel consumption and human cancers. Our results show that peel consumption, the major source of dietary d-limonene, is not uncommon and may have a potential protective effect in relation to skin SCC. Further studies with large sample sizes are needed to more completely evaluate the interrelationships between peel intake, bioavailability of d-limonene, and other lifestyle factors.
 

Altern Med Rev 2002 Aug;7(4):336-9

Calcium-D-glucarate.
 
Calcium-D-glucarate is the calcium salt of D-glucaric acid, a substance produced naturally in small amounts by mammals, including humans. Glucaric acid is also found in many fruits and vegetables with the highest concentrations to be found in oranges, apples, grapefruit, and cruciferous vegetables. Oral supplementation of calcium-D-glucarate has been shown to inhibit beta-glucuronidase, an enzyme produced by colonic microflora and involved in Phase II liver detoxification. Elevated beta-glucuronidase activity is associated with an increased risk for various cancers, particularly hormone-dependent cancers such as breast, prostate, and colon cancers. Other potential clinical applications of oral calcium-D-glucarate include regulation of estrogen metabolism and as a lipid-lowering agent.

 
Adv Exp Med Biol 2002;505:95-111

Potential health benefits from the flavonoids in grape products on vascular disease.
 
Folts JD.
 
Coronary Thrombosis Research Laboratory, University of Wisconsin Medical School, Madison 53792-3248, USA. jdf@medicine.wisc.edu
 
In the dog, monkey, a nd human we have shown that 5 ml/kg of red wine or 5-10 ml/kg of purple grape juice but not orange or grapefruit juice inhibits platelet activity, and protects against epinephrine activation of platelets. Red wine and purple grape juice enhances platelet and endothelial production of nitric oxide (Fitzpatrick et al., 1993, Parker et al., 2000). This is thought to be one of the mechanisms whereby purple grape juice significantly improved endothelial function in 15 patients with coronary artery disease. The consumption of purple grape juice by the patients also offered increased protection against LDL cholesterol oxidation, even though all the patients were also taking another antioxidant vitamin E, 400 IU/day. The number of people and animals in these studies was small; however, each one acted as their own control as measurements were made in each before, and then after consumption of red wine or purple grape juice. Thus these studies are thought to be significant. We feel that the results of these studies are encouraging and justify further research on larger numbers of subjects. This suggests that the flavonoids in purple grape juice and red wine may inhibit the initiation of atherosclerosis by one or more of the mechanisms described above. It will take years to fully characterize the potential benefits of daily consumption of red wine or purple grape juice for maintaining a healthy heart. Based on the existing evidence of antiplatelet and antioxidant benefits and improved endothelial function from red wine and purple grape juice, it seems reasonable to suggest that moderate amounts of red wine or purple grape juice be included among the 5-7 daily servings of fruits and vegetables per day as recommended by the American Heart Association to help reduce the risk of developing cardiovascular disease.

 
Adv Exp Med Biol 2002;505:113-22

Polyphenol antioxidants in citrus juices: in vitro and in vivo studies relevant to heart disease.
 
Vinson JA, Liang X, Proch J, Hontz BA, Dancel J, Sandone N.
 
Department of Chemistry, University of Scranton, PA 18510-4626, USA. vinson@UofS.edu
 
It is well known that eating fruits and vegetables lowers the risk of chronic diseases such as heart disease and cancer. The question of what is/are the active ingredient(s) is still unresolved. The initial hypothesis was that the antioxidant vitamins were responsible. However, recently the polyphenols have been investigated since they have been found to have beneficial properties such as being strong antioxidants. We measured the polyphenol content of citrus juices by an oxidation-reduction colorimetric method (Folin) using catechin as the standard. The order was tangerine juice > grapefruit juice > orange juice. The antioxidant contribution of ascorbic acid was measured by the difference in Folin reactive content following removal by ascorbate oxidase. Ascorbate contributed 56 to 77% of the antioxidant content of orange juice, 46% of the single tangerine juice measured, and 66 to 77% of grapefruit juices. Polyphenol quality in the juices was analyzed by using the inhibition of lower density lipoprotein oxidation promoted by cupric ion, an in vitro model of heart disease. Quality decreased in the following order: orange juice > grapefruit juice > tangerinejuice. In orange juice polyphenols accounted for 84-85% of antioxidant quality. The pure polyphenol hesperidin, which is common in juices, ascorbic acid, and the citrus juices, were not able to bind with LDL+VLDL and protect it from oxidation. In a hamster model of atherosclerosis, the juices were able to significantly inhibit atherosclerosis and lowered cholesterol and triglycerides. Ascorbic acid alone in the dose provided by the juices was found to have the same effect on atherosclerosis. However, the polyphenols in the citrus

 
Circulation 1994 Mar;89(3):1247-53

Inhibition of atherosclerosis by dietary pectin in microswine with sustained hypercholesterolemia.
 
Cerda JJ, Normann SJ, Sullivan MP, Burgin CW, Robbins FL, Vathada S, Leelachaikul P.
 
Department of Medicine, University of Florida College of Medicine, Gainesville.
 
Sustained hypercholesterolemia is a known risk factor for development of atherosclerosis. In animal studies, grapefruit pectin fed concurrently with a high-lipid diet inhibits hypercholesterolemia and atherogenesis. The purpose of the present study was to determine if grapefruit pectin affects cholesterol levels and atherogenesis of animals with established hypercholesterolemia. Microswine were fed an atherogenic diet to establish hypercholesterolemia. Plasma cholesterol levels rose rapidly and for 360 days were sustained at levels 6- to 12-fold the normal level. Then, half the microswine, selected at random, were fed a diet in which 3% grapefruit pectin was substituted for cellulose, and the remaining animals received the original diet. Animals were killed 270 days later, and the extent of atherosclerosis was determined. In animals with established hypercholesterolemia, pectin did not lower their cholesterol levels. However, pectin reduced the extent of atherosclerosis in both the aorta and coronary arteries. The mean surface area covered by atherosclerosis in the aorta was 13.6% in the group that did not receive pectin compared with 5.3% in the group that did receive pectin. The mean coronary artery narrowing was 45% without pectin and 24% with pectin. We conclude that pectin may have a direct beneficial effect on atherosclerosis by a mechanism independent of cholesterol levels.
 

Jpn J Pharmacol 2002 Nov;90(3):247-53

Effects of fragrance inhalation on sympathetic activity in normal adults.
 
Haze S, Sakai K, Gozu Y.
 
Product Development Center, Shiseido Co., Ltd.
 
We investigated the effects of fragrance inhalation on sympathetic activity in normal adult subjects using both power spectral analysis of blood pressure fluctuations and measurement of plasma catecholamine levels. Fragrance inhalation of essential oils, such as pepper oil, estragon oil, fennel oil or grapefruit oil, resulted in 1.5- to 2.5-fold increase in relative sympathetic activity, representing low frequency amplitude of systolic blood pressure (SBP-LF amplitude), compared with inhalation of an odorless solvent, triethyl citrate (P<0.05, each). In contrast, fragrance inhalation of rose oil or patchouli oil caused a 40% decrease in relative sympathetic activity (P<0.01, each). Fragrance inhalation of pepper oil induced a 1.7-fold increase in plasma adrenaline concentration compared with the resting state (P = 0.06), while fragrance inhalation of rose oil caused a 30% decrease in adrenaline concentration (P<0.01). Our results indicate that fragrance inhalation of essential oils may modulate sympathetic activity in normal adults.
 

Nat Prod Lett 2001;15(3):205-10
 
Inhibition of acetylcholinesterase activity by essential oil from Citrus paradisi.
 
Miyazawa M, Tougo H, Ishihara M.
 
Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, Higashiosaka-shi, Osaka, Japan.
 
Inhibition of acetylcholinesterase (AChE) activity by essential oils of Citrus paradisi (grapefruit pink in USA) was studied. Inhibition of AChE was measured by the colorimetric method. Nootkatone and auraptene were isolated from C. paradisi oil and showed 17-24% inhibition of AChE activity at the concentration of 1.62 microg/mL.

 
: J Agric Food Chem 1999 May;47(5):2067-9

Grapefruit gland oil composition is affected by wax application, storage temperature, and storage time.
 
Sun D, Petracek PD.
 
Florida Department of Citrus, Citrus Research and Education Center, Lake Alfred 33850-2299, USA. dsun@icon.lal.ufl.edu
 
The effect of wax application, storage temperature (4 or 21 degrees C), and storage time (14 or 28 days after wax application) on grapefruit gland oil composition was examined by capillary gas chromatography. Wax application decreases nonanal and nootkatone levels. beta-Pinene, alpha-phellandrene, 3-carene, ocimene, octanol, trans-linalool oxide, and cis-p-mentha-2,8-dien-1-ol levels increase, but limonene levels decrease, with temperature. Levels of alpha-pinene, limonene, linalool, citronellal, alpha-terpineol, neral, dodecanal, and alpha-humulene decrease with time. Levels of alpha-phellandrene, 3-carene, ocimene, and trans-linalool oxide increase with time. No compound level was affected by the interactive action of temperature and wax application, suggesting that these two factors cause grapefruit oil gland collapse (postharvest pitting) through means other than changing gland oil composition. Compounds that are toxic to the Caribbean fruit fly (alpha-pinene, limonene, alpha-terpineol, and some aldehydes) decrease with time, thus suggesting grapefruit becomes increasingly susceptible to the fly during storage.

 
: Int J Food Microbiol 1998 Aug 18;43(1-2):73-9

Relationship between volatile components of citrus fruit essential oils and antimicrobial action on Penicillium digitatum and penicillium italicum.
 
Caccioni DR, Guizzardi M, Biondi DM, Renda A, Ruberto G.
 
CRIOF-University of Bologna, Italy.
 
This study examined the effect of volatile components of citrus fruit essential oils on P. digitatum and P. italicum growth. The hydrodistilled essential oils of orange (Citrus sinensis cvv. “Washington navel”, “Sanguinello”, “Tarocco”, “Moro”, “Valencia late”, and “Ovale”), bitter (sour) orange (C. aurantium), mandarin (C. deliciosa cv. “Avana”), grapefruit (C. paradisi cvv. “Marsh seedless” and “Red Blush”), citrange (C. sinensis x Poncirus trifoliata cvv. “Carrizo” and “Troyer”), and lemon (C. limon cv. “Femminello”, collected in three periods), were characterized by a combination of GC and GC/MS analyses. The antifungal efficacy of the oils was then examined at progressively reduced rates. Findings showed a positive correlation between monoterpenes other than limonene and sesquiterpene content of the oils and the pathogen fungi inhibition. The best results were shown by the citrange oils, whose chemical composition is reported for the first time, and lemon. Furthermore P. digitatum was found to be more sensitive to the inhibitory action of the oils.

 
J Egypt Soc Parasitol 1998 Aug;28(2):595-606

Insecticidal properties of citrus oils against Culex pipiens and Musca domestica.
 
Shalaby AA, Allam KA, Mostafa AA, Fahmy SM.
 
Research Institute of Medical Entomology, Dokki, Cairo, Egypt.
 
Peel oils of lemon, grapefruit and navel orange were tested for insecticidal activities against larvae and adults of Culex pipiens and Musca domestica. Lemon peel oil was the most effective against larvae and adults of C. pipiens. Grapefruit peel oil was more toxic to adults of M. domestica while lemon oil, was more toxic Musca larvae. On the other hand, the orange peel oil was the least effective against larvae and adults of both species. The toxicity of oils applied to larval stages was extended to pupal and adult stages. C. pipiens adults appeared with paralyzed legs, while M domestica adults appeared normal. The weights of pupae treated as larvae were generally less than that of the control. All oils produced deleterious effects on fecundity of survivors of sublethal doses. The effect was obviously recorded in treated adults. Treatment of Culex & Musca with oils caused serious latent effect.
 

J Altern Complement Med 2002 Jun;8(3):333-40
Erratum in:
‘P J Altern Complement Med 2002 Aug;8(4):521. Reagor Lana [corrected to Reagor Lee]

The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity.
 
Heggers JP, Cottingham J, Gusman J, Reagor L, McCoy L, Carino E, Cox R, Zhao JG, Reagor L.
 
Department of Surgery (Plastic), School of Medicine, University of Texas Medical Branch, Galveston, USA. jphegger@utmb.edu
 
OBJECTIVES: Recent testimonials report grapefruit-seed extract, or GSE (Citricidal) to be effective against more than 800 bacterial and viral strains, 100 strains of fungus, and a large number of single and multicelled parasites. This study investigated GSE for antibacterial activity at varying time intervals and concentration levels and tissue toxicity at varying concentrations in an effort to determine if a concentration existed that was both microbicidal and nontoxic and in what period of time. DESIGN: Gram-negative and gram-positive isolates were introduced into graduated dilutions of GSE (twofold concentrations ranging from 1:1, through 1:512) for determination of bacterial activity. In vitro assays with human skin fibroblast cells were also performed at the same dilutions to determine toxicity. RESULTS: These tests indicated that from the 1:1 through the 1:128 concentrations, GSE remained toxic as well as bactericidal. However, test results indicated that at the 1:512 dilution, GSE remained bactericidal, but completely nontoxic. CONCLUSIONS: The initial data shows GSE to have antimicrobial properties against a wide range of gram-negative and gram-positive organisms at dilutions found to be safe. With the aid of scanning transmission electron microscopy (STEM), the mechanism of GSE's antibacterial activity was revealed. It was evident that GSE disrupts the bacterial membrane and liberates the cytoplasmic contents within 15 minutes after contact even at more dilute concentrations.