Citrus paradisi Macfad.

Last updated: 22 August 2016

Scientific Name

Citrus paradisi Macfad.


No synonyms available.  [1]

Vernacular Name

English Grapefruit [2]
Indonesia Limau gedang [2].
Thailand Grapefruit [2]
Laos kièngz s'aangz [2]
Cambodia Krôôch thlông [2]
Vietnam cam, bu'o 'I [2]
France Pomelo [2]
Papua New Guinea Muli (Pidgin) [2]

Geographical Distributions

Citrus paradisi is the only major citrus fruit that originated outside South-East Asia; probably on the island of Barbados (West Indies) around 1750. It is thought to be either an interspecific hybrid of pummelo (Citrus maxima (Burm.) Merr.) and sweet orange (Citrus sinensis (L.) Osbeck) or hybrid/mutant pummelo. Nowadays it is widely grown everywhere in the tropics and the warmer subtropics, with Florida (United States) and Israel as main producers. In South-East Asia, the tree and the fruit are rarely encountered, pummelo dominating throughout the region. [2]

Botanical Description

C. paradisi belongs to the Rutacea family. It is a large spreading evergreen tree, 10—15 m tall, with a round top and dense foliage; twigs angular when young, (sub) glabrous. [2]

The leaves smaller than those of pummelo, larger than sweet orange leaves, nearly glabrous; petioles broadly winged but less than in pummelo, wing oblanceolate to obovate; blade ovate, 7—15 cm x 4—8 cm, often crenulate. [2]

The flowers axillary, singly or in small clusters, 4—5 cm in diameter, pentamerous; calyx 5-lobed; petals white, smaller than those of pummelo, larger than in sweet orange; stamens 20—25; ovary-cells 12—14. [2]

The fruit a berry, mainly borne in clusters, usually globose, 8—15 cm in diameter, greenish-yellow; segments coherent and not easily separable, smaller but containing more juicy pulp-vesicles than in pummelo. The seeds are white, smooth, usually polyembryonic. [2]


In general, culture of grapefruit is similar to that of the orange except that wider spacing is necessary. [3]

Nutritional experiments with grapefruit have shown that excessive nitrogen results in malformed fruit, coarser texture and less juice. Lack of certain minor elements is evident in symptoms often mistaken for disease. The condition called exanthema is caused by copper deficiency; mottle leaf results from zinc deficiency. [3]

Soil Suitability and Climate Requirement

C. paradisi needs a warmer climate than sweet orange: 3000 degree-days or more (one degree-day is the difference between the average temperature and 13°C). It should therefore not be grown at elevations above 800 m. At sea level, near the equator, maturity is reached in 8—9 months. At higher altitudes or latitudes it takes 10 months or more. Most grapefruits grow on sandy soils, but the crop also grows well on heavy clay soils with good drainage.[2]

The grapefruit is grown on a range of soil types. Within USA, in the main growing area of Florida, the soil is mildly acid sand and applications of lime may be beneficial. On the east coast there are coquina shell deposits and, in the extreme southern part of the peninsula, there is little soil mixed with the prevailing oolitic limestone. Where the grapefruit is grown in California, Arizona and Texas, the soils are largely alkaline and frequent irrigation causes undesirable alkaline salts to rise to the surface. In Surinam, grapefruit is grown on clay. Successful grapefruit culture depends mainly on the choice of rootstock best adapted to each type of soil. Salinity of the soil and in irrigation water retards water uptake by the root system and reduces yields. [3]

Field Preparation

No documentation

Field Planting

No documentation

Field maintenance

No documentation

Pest and Disease Control

The grapefruit is subject to most of the same pests that attack the orange, including Caribbean and Mediterranean fruit flies. In addition to the cold treatment referred to above, irradiation has been studied as a method of disinfection, but has not been authorized for citrus fruit treatment. Exposure of early-season fruit to 60 and 90 krad causes scald and rind breakdown after 28 days of storage, and mainly pitting in midseason and late fruits. Minimal injury results from exposure to 7.5, 15, and 30 krad. [3]

The following diseases have been reported for the grapefruit tree and its fruit by the Florida Division of Plant Industry: leaf spot (Alternaria citri, Mycosphaerella horii, Phyllosticta hesperidearum); algal leaf spot (Cephaleuros virescens); greasy spot (Cercospora citri-grisea); tar spot (C. gigantea); anthracnose (Colletotrichum gloeosporioides); thread blight (Corticium koleroga and C. stevensii); gummosis(Diaporthe citri); dieback (Diplodia natalensis); heart rot (Fomes applanatus, Ganoderma sessilis, and Xylaria polymorpha); charcoal root rot (Macrophomina phaseolina); root rot (Fusarium oxysporum);sooty blotch (Gloeodes pomigena); flyspeck (Leptothyrium pomi); mushroom root rot (Clitocybe tabescens); foot rot (Phytophthora megasperma, P. palmivora, and Pparasitica); damping-off (Rhizoctonia solani); seedling blight (Sclerotium rolfsii); felt fungus, (Septobasidium pseudopedi- cellatum); branch knot (Sphaeropsis tumefaciens); leaves may be attacked by Chaetothyricum hawaiiense, and twigs byPhysalospora fusca. Brown rot of fruit is caused by Phytophthora citrophthora and P. terrestris; stem-end rot, Botryosphaeria ribis; dry rot of fruit (Nematospora coryli); green mold (Penicillium digitatum); blue mold, (P. italicum); pink mold (P. roseum); scab (Elsinoe fawcetti). [3]

The tree is highly susceptible to citrus canker and several viruses: crinkly leaf virus, psoriasis, tristeza, xyloporosis, and infectious variegation. Mesophyll collapse is caused by extreme drought and dehydrating wind. [3]


In Florida, all commercial cultivars reach legal maturity in September or October if sprayed after blooming with lead arsenate to reduce acidity. Even after legal maturity the grapefruit can be "stored" on the tree for months, merely increasing in size, and extending the marketing season. The fruits can be harvested until near the end of May when they begin to fall and seeds start sprouting in the fruit. The only adverse effect of late harvesting is a corresponding reduction in the following year's crop. It has been found that spot-picking of the largest fruits partially counteracts this effect of late harvest. Fruit drop can be retarded by spraying with a combination of gibberellic acid and 2,4-D. Either of these agents or both together will reduce the germination of seeds. Germination may be inhibited for periods up to 11 weeks by cool storage at 50º F (10º C). [3]

Grapefruits were formerly harvested by climbing the trees or using picking hooks which frequently damaged the fruit. Today, the fruits on low branches are picked by hand from the ground; higher fruits are usually harvested by workers on ladders who snap the stems or clip the fruits as required. California began utilizing a modified olive limb-shaker for harvesting grapefruit in 1972. The machines work in pairs to harvest opposite sides of each tree and the trees must be pruned to remove deadwood and to give access to 3-5 main limbs for shaking. Lower branches must be lopped off to leave a clear 2 1/2 ft (75 cm) space for the catching frame. Mechanical harvesting causes some superficial injury. A team of 3 workers with one machine can harvest 150 to 188 field boxes50 lbs (22.7 kg) when filledper hour, as compared with 45 boxes per hour for 3 manual pickers. Stems are removed from the fruits before packing to avoid stem-damage. [3]

Early in the season, when the fruits are mature but not fully colored, they are often degreened by exposure to ethylene gas. The grapefruit is remarkable for its durability, but modern practices of applying fungicide to the harvested fruit are given credit for the great reduction in marketing losses. The cull rate in New York wholesale warehouses in 1983 was found to be 1.4% (mostly fungal), as compared with 13 % estimated in 1960. Retail losses in 1983 were 3.5%, and only a small proportion were the result of physical injury. [3]

Postharvest handling

The grapefruit keeps well at 65º F (18.33º C) or higher for a week or more and for 2 or 3 weeks in the fruit/vegetable compartment of the home refrigerator. The first sign of breakdown is dehydration and collapse of the stem-end. To retard moisture loss, fruits for marketing are washed and waxed as soon as possible after harvest. When kept in prolonged storage, the grapefruit is subject to chilling injury (peel pitting) at temperatures below 50º F (10º C). The degree of injury depends on several factors: the fruits on the outside of the tree are more susceptible than the fruits that have been sheltered by foliage. The use of preharvest growth regulators tends to reduce susceptibility, as does 100% relative humidity during storage. Preconditioning at 60.8º F (16º C) for 7 days before storing at 33.8º F (1º C) prevents injury. Lowering the temperature gradually after preconditioning is also beneficial, as is sealing the fruit in polyethylene shrink-film before refrigerating. [3]

The banning of ethylene dibromide fumigation except for export has made it necessary to resort to cold treatment as an alternative measure against fruit fly infestation for shipment to Texas, Arizona and California. The United States Department of Agriculture now requires that imported citrus fruits be kept at 32º F (0º C) for 10 days or at 36º F (2.2º C) for 16 days after the fruit has been cooled down to the specified temperature. In Israel, investigators have found that waxing with a coating containing fungicide, and holding the packed fruit for 6 days at 62.6º F (17º C) before the cold treatment, gives good protection from chilling injury and decay in storage. Cold treatment costs 5 times as much as fumigation with ethylene dibromide. Methyl bromide has been tested and proposed as an effective fumigant. [3]

Estimated cost of production

No documentation

Chemical Constituent

Grapefruit has been found to contain monoterpene hydro carbons (limonene and myrcene), sesquiterpenes (nootkatone), alcohols, aldehydes, esters, flavonoid glycosides (naringin). [4][5][6][7]

Plant Part Used

No documentation

Traditional Use

Grapefruit oil and/or its constituents can be found in the food and beverage industry as flavouring for soft drinks, ice cream and chocolates. [1] It is commonly used in fruit cups or fruit salads, in gelatins or puddings and tarts. They are commercially canned in syrup. In Australia, grapefruit is commercially processed as marmalade. It may also be made into jelly. [2]

The juice is marketed as a beverage fresh, canned, or dehydrated as powder, or concentrated and frozen. It can be made into an excellent vinegar or carefully fermented as wine. [2]

Grapefruit peel is candied and is an important source of pectin for the preservation of other fruits. The peel oil, expressed or distilled, is commonly employed in soft-drink flavor, after the removal of 50% of the monoterpenes. [3]

Old grapefruit trees can be salvaged for their wood. The sapwood is pale-yellow or nearly white, the heartwood yellow to brownish, hard, fine-grained, and useful for domestic purposes. Mainly, pruned branches and felled trees are cut up for firewood. [3]

An essence prepared from the flowers is taken to overcome insomnia, also as a stomachic, and cardiac tonic. The pulp is considered an effective aid in the treatment of urinary disorders. Leaf extractions have shown antibiotic activity. [3]

After oil extraction, the seed hulls can be used for soil conditioning, or, combined with the dried pulp, as cattlefeed. A detoxification process must precede the feeding of this product to pigs or poultry. The waste from grapefruit packing plants has long been converted into molasses for cattle. [3]

Preclinical Data


Olfactory Stimulant activity

Animal studies have indicated that inhalation of grapefruit oil can have a strong stimulant effect, increasing sympathetic activity as well as blood pressure. [8] This olfactory stimulation with grapefruit oil also exhibited decreases in appetite and increases body temperature in rats. The limonene content is thought to be responsible for this action. [9]

Appetite Suppressant activity

The appetite suppressant activity has been further supported in an additional animal model whereby use of the oil resulted in lipolysis which then decreased body weight and suppressed the appetite. This action is attributed to limonene. [4]

Antioxidant activity

Grapefruit and its oils have been shown to inhibit the Cytochrome P450 enzyme thereby increasing the oral metabolism of several prescription and OTC drugs. In laboratory analysis, chemical constituents were identified (furocoumarins: bergaptol and geranylcoumarin) that inhibited P450 and also demonstrated radical scavenging activity. [10]

Antimicrobial Activity 

Methicillin-resistant Staphylococcus aureus (MRSA) bacterial strains are usually resistant to antibacterial drugs such as ethidium bromide and norfloxacin. However, in a laboratory setting, the addition of constituents of C. paradisi oil resulted in the action of these drugs against MRSA greatly being greatly improved. [11][12]

In vitro screening of a grapefruit seed extract found bactericidal activity against gram negative and positive bacteria to dilutions up to 1:512. [13][14] In a series of case reports, chewing and swallowing 5 to 6 grapefruit seeds every 8 hours was effective against Klebsiella , Staphylococcus aureus , and Escherichia coli urinary tract infections, but not against Pseudomonas aeruginosa -resistant strains. [15]

Grapefruit seed may also inhibit the growth of two bacteria specie that can cause gastrointestinal ulcers, H. pylori and C. jejuni. Studies suggest that inhibition of these bacteria can prevent such ulcers. [16] Grapefruit seed may also inhibit the growth of Candida, a fungus that can affect bowel health and destroy the normal, helpful bacteria that reside in the gastrointestinal system. [17] The polymethoxyflavones content in grapefruit seed extract was reported to be effective as an antifungal against Penicillium digitatum. [18]

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. [19]

Apoptotic acitivity

Several citrus essential oils were studied for potential induction of apoptosis in human leukemic (HL-60) cells. All oils including grapefruit demonstrated apoptotic activity. Researchers determined that constituents other than limonene may be responsible for this action. [6]


No documentation

Clinical Data

Clinical findings

Limited clinical trials have been undertaken, possibly due to the potential for drug interactions. Two trials conducted in post-coronary bypass patients with atherosclerosis demonstrated improved lipid profiles following whole grapefruit and grapefruit juice consumption. [19][20] Antioxidant-carrying capacity also improved. Systolic and diastolic blood pressure were unchanged throughout the 30-day study, contrary to results of another study that showed a hypotensive effect for consumption of a hybrid grapefruit/pummelo juice, possibly due to the flavonoid component. [21][22] Prolongation of the QTc interval has also been demonstrated in healthy volunteers, as well as in patients with cardiomyopathy, possibly due to the naringenin glycoside content. [23][24]

Side effects

No documentation

Pregnancy/Breast Feeding

No documentation

Adverse reaction

Reports of adverse reactions to grapefruit consumption are limited. Grapefruit juice has been associated with hypotension [21]and deep vein thrombosis (presumed to be due to an interaction with ethinyl estradiol). [25] Prolongation of the QTc interval has been demonstrated in healthy volunteers and patients with cardiomyopathy. [23][24] Case reports exist of allergy to pectin and pectin-induced asthma. [26]

Drug interactions

Grapefruit seed extract is not reported to contain naringin, the constituent in grapefruit juice that may alter the metabolism of certain medications. [27] 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. [28]


Quality clinical trials upon which to base therapeutic dosing recommendations are limited. Improved lipid profiles were achieved with consumption of 1 grapefruit daily for 30 days. [20] Grapefruit juice 8 oz (237 mL), or half of a fresh grapefruit, 3 times a day before each meal for 12 weeks resulted in weight loss in a clinical trial evaluating the effect on metabolic syndrome. [29] As a nutritional supplement, consumption of 2 grapefruits a day improved the vitamin C status of patients with periodontitis after 2 weeks. [30]

Poisonous Management

No documentation

Line drawing

No documentation


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  3. Morton J. Grapefruit. In: Fruits of warm climates. Miami, Florida: Julia F. Morton, 1987; p. 152–158
  4. Shen J, Niijima A, Tanida M, Horii Y, Maeda K, Nagai K. Olfactory stimulation with scent of grapefruit oil affects autonomic nerves, lipolysis and appetite in rats. Neurosci Lett. 2005;380(3):289-294.
  5. Feger W, Brandauer H, Gabris P, Ziegler H. Nonvolatiles of commercial lime and grapefruit oils separated by high-speed countercurrent chromatography. J Agric Food Chem. 2006:54(6):2242-2252.
  6. Hata T, Sakaguchi I, Mori M, et al. Induction of apoptosis by Citrus paradisi essential oil in human leukemic (HL-60) cells. In Vivo. 2003;17(6):553-559.
  7. Kirbaslar SI, Boz I, Kirbaslar FG. Composition of Turkish lemon and grapefruit peel oils. J Essent Oil Res;18 (5):525-543.
  8. Tanida M, Shen J, Niijima A, et al. Effects of olfactory stimulations with scents of grapefruit and lavender oils on renal sympathetic nerve and blood pressure in Clock mutant mice. Auton Neurosci. 2008;139(1-2):1-8.
  9. Tanida M, Niijima A, Shen J, Nakamura T, Nagai K. Olfactory stimulation with scent of essential oil of grapefruit affects autonomic neurotransmission and blood pressure. Brain Res. 2005;1058(1-2):44-55.
  10. Girennavar B, Jayaprakasha GK, Jadegoud Y, Nagana Gowda GA, Patil BS. Radical scavenging and cytochrome P450 3A4 inhibitory activity of bergaptol and geranylcoumarin from grapefruit. Bioorg Med Chem. 2007;15(11):3684-3691.
  11. Abulrob AN, Suller MT, Gumbleton M, Simons C, Russell AD. Identification and biological evaluation of grapefruit oil components as potential novel efflux pump modulators in methicillin-resistant Staphylococcus aureus bacterial strains. Phytochemistry. 2004;65(22):3021-3027.
  12. Reagor L, Gusman J, McCoy L, Carino E, Heggers JP. The effectiveness of processed grapefruit-seed extract as an antibacterial agent: I. An in vitro agar assay. J Altern Complement Med. 2002;8(3):325-332.
  13. Heggers JP, Cottingham J, Gusman J, et al. The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity. J Altern Complement Med. 2002;8(3):333-340.
  14. 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;11(2):369-371.
  15. Arimi SM. Campylobacter infection in humans. East Afr Med J. 1989;66(12):851-855.
  16. Ionescu G, et al. Oral Citrus seed extract. J Orthomolecula Med. 1990;5(3):72-74.
  17. Ortuño A, Báidez A, Gómez P, et al. Citrus paradisi and Citrus sinensis flavonoids: Their influence in the defence mechanism against Penicillium digitatum. Food Chem. 2006;98(2):351-358.
  18. Fitzgerald JF. Colonization of the gastrointestinal tract. Mead Johnson Symp Perinat Dev Med. 1977;(11):35-38.
  19. Gorinstein S, Caspi A, Libman I, Katrich E, Lerner HT, Trakhtenberg S. Fresh israeli jaffa sweetie juice consumption improves lipid metabolism and increases antioxidant capacity in hypercholesterolemic patients suffering from coronary artery disease: studies in vitro and in humans and positive changes in albumin and fibrinogen fractions. J Agric Food Chem. 2004;52(16):5215-5222.
  20. Gorinstein S, Caspi A, Libman I, et al. Red grapefruit positively influences serum triglyceride level in patients suffering from coronary atherosclerosis: Studies in vitro and in humans. J Agric Food Chem. 2006;54(5):1887-1892.
  21. Reshef N, Hayari Y, Goren C, Boaz M, Madar Z, Knobler H. Antihypertensive effect of sweetie fruit in patients with stage I hypertension. Am J Hypertens. 2005;18(10):1360-1363.
  22. Nilsson I. Grapefruit juice caused hypotension. Lakartidningen. 1997;94(3):112-113. Swedish.
  23. Zitron E, Scholz E, Owen RW, et al. QTc prolongation by grapefruit juice and its potential pharmacological basis: HERG channel blockade by flavonoids. Circulation. 2005;111(7):835-838
  24. Piccirillo G, Magrì D, Matera S, et al. Effects of pink grapefruit juice on QT variability in patients with dilated or hypertensive cardiomyopathy and in healthy subjects. Transl Res. 2008;151(5):267-272.
  25. Grande LA, Mendez RD, Krug RT, Verschuyl EJ. Attention—grapefruit! Lancet. 2009;373(9670):1222.
  26. Ferdman RM, Ong PY, Church JA. Pectin anaphylaxis and possible association with cashew allergy. Ann Allergy Asthma Immunol. 2006;97(6):759-760.
  27. Bailey DG, Malcolm J, Arnold O, Spence JD. Grapefruit juice-drug interactions. Br J Clin Pharmacol. 1998;46(2):101-110.
  28. 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.
  29. Fujioka K, Greenway F, Sheard J, Ying Y. The effects of grapefruit on weight and insulin resistance: Relationship to the metabolic syndrome. J Med Food. 2006;9(1):49-54.
  30. Staudte H, Sigusch BW, Glockmann E. Grapefruit consumption improves vitamin C status in periodontitis patients. Br Dent J. 2005;199(4):213-217.