The wonders of grapefruit oil

The oil of Citrus paradisi or Grapefruit is one of the ingredients in the griffin+row Cleanse, Nourish and Enrich products. With an exotic name that invokes visions of heavenly perfection, the essential oil derived from this fruit has gained popularity in recent times. As a member of the Citrus family of fruit, one would expect that the essential oil would share properties of other citrine fellows. It does…and yet, there seems to be something remarkable about this oil that has caught the attention of scientists, doctors and cosmetologists. Read on to find out how a miniscule quantity of a unique molecule has become the signature identity of Citrus paradisi and how it could possibly affect our health.

Introducing Citrus paradisi

Citrus paradisi is commonly referred to as Grapefruit because the fruit grow in clusters, like grapes. The fruit is a relatively new member of the Citrus family, being a hybrid of the pomelo (Citrus grandi) and the sweet orange (Citrus sinensis) 1. So while it retains the large size and the clustered fruiting pattern of the pomelo, it derives its sweetness and possibly some of the colour from the sweet orange. Not surprisingly, it is also called Citrus maxima for its large size and Citrus racemose for the clustered fruit.

This fruit has its origins in Barbados. It is thought that the pomelo was brought to the sunny Caribbean island by one Captain Shaddock of the erstwhile East India Company on his way to England. The pomelo (which, incidentally, is also called Shaddock tree) was accidentally cross-bred with the orange trees that had been brought to the islands 200 years earlier by Christopher Columbus. The hybrid citrus fruit that took seed and flourished on the island was then recognised as a different species and given the name Citrus paradisi by the botanist James Macfayden in 1828. Although grapefruit is now referred to as one of the seven wonders of Barbados, a couple of centuries ago the same fruit was called the ‘Forbidden Fruit’!

Grapefruit is widely cultivated in several countries including USA, Brazil and Israel. In the USA, natural and radiation induced 2 mutations have been used to select for red varieties of grapefruit, since the redder the pulp, sweeter the fruit.  

Traditional uses of Citrus paradisi

 

The genus Citrus is native to south-east Asia. There are innumerable species of citrus fruits ranging from lemon to lime and sweet orange. Most of these have found a use in traditional medicine systems due to their high content of polyphenols, flavonoids and terpenes.

Medicinal uses:

Traditional Chinese medicine recommends grapefruit as a ‘cooling food’ for individuals who are diagnosed with excess body heat 3 The fruit became a popular breakfast fruit in the West with the belief that it helps in weight loss and works as a diuretic 4.

Citrus fruit peels have been extensively used in relaxation therapy.

Disinfectant uses:

Grapefruit oil has insecticidal activity. It is effective against ticks and mosquitos and possibly useful against bedbugs, etc. 5.

Culinary uses:

The Asiatic counterparts of the grapefruit have been used in salads and to add some zing to dishes. In several parts of south-east Asia grapefruit is simply eaten with a sprinkling of salt, chilli powder and sugar. In the West, grapefruit is a common breakfast fruit, eaten with or without sugar.

Bioactivity and associated components of the plant

 

Phytonutrients such as lycopene, β- carotene and cryptoxanthin- β confer the reddish-pink colour on the pulp of the grapefruit. This edible part is rich polyphenols, flavonoids, vitamins A, C and B vitamins like folate, pyridoxine, riboflavin, niacin and pantothenic acid. Minerals such as calcium, copper, magnesium, zinc, manganese, iron and phosphorus are also present in significant quantities 4. The slight bitter taste of grapefruit pulp is due to the flavonoid naringin. Naringin protects the skin against harmful UV-B rays 6.

The inedible white part of the fruit together with the seeds is marketed as “grapefruit seed extract (GSE)”. GSE is believed to have antimicrobial activity, although this has not been conclusively proven 7.

Oil can be extracted from the glossy dark green leaves as well as the rind of the fruit.

  1. Grapefruit leaf oil has a defined citrus fragrance. It mainly contains sabinene and β-ocimene. A small percentage of other compounds such as p-cymene, terpinen-4-ol, linalool and limonene are also present 89
  2. Grapefruit oil is extracted from the rind of the fruit. The major component of grapefruit oil are the terpenes limonene (>97%) and myrcene (<2%) 10. α-pinene, sabinene, geraniol, citronellal, linalool, decyl acetate, neryl acetate and terpinen-4-ol are present in trace amounts 11. Nootkatone, an important sesquiterpene, is also present in miniscule amounts 12.

Limonene and Nootkatone: a spotlight on the main bioactive components

  • Limonene is a cyclic terpene.  

Limonene is responsible for the characteristic smell of all citrus fruits. It is used in the perfumery industry for its fresh and woody fragrance and as a food additive to mask the bitter taste of alkaloids.

  • Nootkatone is a sesquiterpene and a ketone.  

Nootkatone is the compound that gives the distinctive flavour and odour to grapefruit. It is now the signature molecule to identify genuine grapefruit oil since other citrus fruit oils do not contain or contain negligible amounts of nootkatone. Besides grapefruit, nootkatone is found in the Alaskan yellow cedar and vetiver grass 13.

General health benefits and uses of grapefruit oil:

Like all oils derived from citrus fruits, grapefruit oil is extracted from the pericarp (rind) of the ripe fruit. The rind is carefully separated from the pulp and sliced for cold pressing. Oil can also be extracted by directly soaking the rind in carrier oils such as almond or coconut for 8 weeks or with mild heat for 8 hours. Steam distillation is another method to extract the essential oil from the rind 14. The quality of grapefruit oil depends on the method of cultivation since any pesticide sprayed on the fruit gets concentrated in the oil. Oil extracted from organically grown fruit is the best for use as a medicine and in cosmetics.

Grapefruit oil is light yellow in colour. It is non-viscous with volatile components that make it ideal for use as a top note in the perfumery industry. It is non-toxic and used after suitable dilution in compatible carrier oils. There have been no reports of adverse reactions and hence it is classified as non-irritant and non-sensitising. It is stored in dark bottles and although non-phototoxic, may cause some irritation if exposed to direct sunlight immediately after application 11.

Pharmacological uses of grapefruit oil:

Unlike grapefruit juice which has a proven medicinal use, studies on grapefruit oil is still in its infancy. Yet the oil has become the darling of cosmetologists for its purported action on cellulite, water retention and removal of toxins 4. While grapefruit juice has unequivocally been shown to alleviate symptoms of (what is now called) the metabolic syndrome, there are some early indications of the positive effect of the oil on hypertension and diabetes. Some of the proven medicinal uses of grapefruit oil are listed below-

  • Antibacterial activity: In vitro studies have shown a potent antibacterial activity of grapefruit oil against Propionibacterium acnes, one of the major causes of recurrent acne outbreaks 15. In another study, the oil was found to inhibit the growth of Staphylococcus aureus and Staphylococcus epidermidis which are responsible for the formation of pus in pimples 16.
  • Antifungal activity: Grapefruit oil has been proven to have antifungal activity 17, especially against Penicillium spp. 18
  • Antioxidant effects: Citrus paradisi (pink) oil has been shown to have better in vitro free-radical quenching activity as compared to its parent Citrus grandi 10. The overall anti-oxidant activity of grapefruit oil suggests that it could reduce free-radical induced cellular damage and consequently aging. 
  • Anticancer activity: Although there is no conclusive evidence in animals, in vitro studies using cell lines have revealed the cytotoxic effect of grapefruit oil on cancerous cells 15.
  • Cellulite reduction: Nootkatone present in grapefruit oil has been shown to affect AMPK (AMP kinase), an enzyme that is central to energy utilisation and consequently, burning of excess fat 19.
  • Odour management in fungating wounds: A study involving patients suffering from squamous cell carcinoma showed that a blend of grapefruit, tea tree and eucalyptus oils along with a regular Betadine swab resulted in a complete recovery from the necrotising malodorous wounds 20.
  • Insecticidal activity: A natural insecticide, grapefruit oil is especially effective against ticks and mosquitoes 5.

Use in the food industry: In addition to the above, grapefruit oil is used as a safe flavouring agent in foods and beverages.

Use in the cosmetic industry: As described earlier, grapefruit oil has the capacity to ‘melt’ cellulite making it a must-have ingredient in massage oils. Incorporating the oil in face washes and creams confers some protection against acne-causing bacteria.

Use in aromatherapy: Olfactory stimulation by grapefruit oil has been shown to trigger metabolic pathways leading to the breakdown of fat, increased blood pressure and decreased food intake 21. This makes the oil an attractive option for those who wish to lose weight without strenuous exercise.

Botany and grow it yourself

The grapefruit, like its parent – the pomelo- is one of the largest fruits of the citrus family and can easily weigh 1-1.5 kg. The tree belongs to the family Rutaceae and grows to a height of 15-30 ft. The leaves are dark green and glossy, 5-20 cm long and 2-15 cm wide. The white flowers that bloom in clusters of 2-8 at the end of the branches have a beautiful citrus fragrance. The large fruit that form from the flowers often weigh down the branches. The fruit are green when unripe and slowly turn yellow upon ripening. The essential oil is extracted from the rind of the fruit.

Propagation is by seeds and cuttings. Grapefruit grows well in tropical to semi-tropical climates 1.

Glossary

Terpene: A class of volatile aromatic compound characterised by the presence of two isoprene units (4-carbon units with alternating double bonds). Pinene (from pine), myrcene (from hops), limonene (from citrus fruits) and linalool (from lavender) are monoterpenes. Nootkatone contains 3 isoprene units and is a sesquiterpenes.

Polyphenols: A class of naturally occurring compounds that contain several phenolic groups linked together. Derived from plants, polyphenols are important anti-oxidant compounds. Tannin (present in tea) is one of the best-known polyphenols.

Flavonoids: Flavonoids are a subclass of polyphenols that have two six-membered carbon rings and one oxygen- containing heterocyclic ring. The name is derived from the typically yellow colour of the compounds. Flavonoids are present in plants and fungi. They have been shown to have antimicrobial, anticancer and antioxidant activities.

Metabolic syndrome: A cluster of disorders including hypertension (high blood pressure), dyslipidemia (alteration in the level of circulating triglycerides and cholesterol), insulin –resistant diabetes (high blood sugar due to impaired insulin action) and central obesity (fat deposition around the abdomen). Metabolic syndrome is a condition generated by unhealthy eating habits and a sedentary lifestyle. 

Cellulite: Cellulite is an uneven deposit of fat just below the surface of the skin, especially in women. The accumulation of cellulite increases with age and is associated with a breakdown of collagen. While not really a disease condition, cellulite is a cosmetic problem because of the unsightly ‘cottage cheese’ look of the skin.


References and Sources

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  2. Texas grapefruit history. Retrieved on June 29, 2017 from http://www.texasweet.com/texas-grapefruits-and-oranges/texas-grapefruit-history/
  3. Lu Y, Zhang C, Bucheli P, Wei D. (2006). Citrus flavonoids in fruit and traditional Chinese medicinal food ingredients in China. Plant Foods & Human Nutrition. 61(2): 57-65.
  4. The benefits of Grapefruit, the “Fruit of Paradise” (2008). Retrieved on June 30, 2017 from https://www.findatopdoc.com/Healthy-Living/The-Benefits-of-Grapefruit-the-Fruit-of-Paradise
  5. Substances that give grapefruit its flavour and aroma could give insect pests the boot (2013, September 11). Retrieved on June 30, 2017 from https://www.acs.org/content/acs/en/pressroom/newsreleases/2013/september/substance-that-gives-grapefruit-its-flavor-and-aroma-could-give-insect-pests-the-boot.html
  6. Ren X, Shi Y, Zhao D, Xu M, Li X, Dang Y, Ye X.(2016). Naringin protects ultraviolet B-induced skin damage by regulating p38 MAPK signal pathway. Journal of Dermatological Sciences. 82(2):106-114.
  7. von Woedtke T, Schlüter B, Pflegel P, Lindequist U, Jülich WD.(1999). Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained. 54(6):452-456.
  8. Franz C and Novak J in “Sources of essential oils” in “Handbook of essential oils: science, technology and applications. (2010). Edited by K. Hüsnü Can Baser and Gerhard Buchbauer, CRC Press, p 65.
  9. Ekundayo O, Bakare O, Adesomoju A and Stahl-Biskup E. (1991). Composition of the leaf oil of grapefruit (Citrus paradisi). Journal of Essential Oil Research.3(1): 55-56.
  10. Ou M-C, Liu Y-H, Sun Y-W and Chan C-F. (2015).The composition, antioxidant and antibacterial activities of cold-pressed and distilled essential oils ofCitrus paradisi and Citrus grandis (L.) Osbeck. Evidence-Based Complementary and Alternative Medicine : eCAM2015, 804091. http://doi.org/10.1155/2015/804091
  11. Grapefruit essential oil information. (2017, June 30). Retrieved on June 30, 2017 from http://essentialoils.co.za/essential-oils/grapefruit.htm
  12. Sell, C in “Chemistry of essential oils” in “Handbook of essential oils: science, technology and applications. (2010). Edited by K. Hüsnü Can Baser Gerhard and Buchbauer, CRC Press, p 139.
  13. National Center for Biotechnology Information. PubChem Compound Database; CID=1268142, https://pubchem.ncbi.nlm.nih.gov/compound/1268142/a> (accessed July 5, 2017).National Center for Biotechnology information, PubChem Compound database; CID= 1268142National Center for Biotechnology Information. PubChem Compound Database; CID=1268142, (accessed July 5, 2017).,https://pubchem.ncbi.nlm.nih.gov/compound/1268142 (accessed July 3, 2017)
  14. Subramanian A, Ananthan S, Vignesh M, Selva Bharathi SP and Thirumarimurugan M. (2014). 5th International Conference on Chemical Engineering and Applications IPNACBEE 74:7.
  15. Zu Y, Yu H, Liang L, Fu Y, Efferth T, Liu X and Wu N. (2010). Activities of ten essential oils towards Propionibacterium acnesand PC-3, A-549 and MCF-7 cancer cells. Molecules 15(5): 3200-3210.
  16. Uysal B, Sozmen F, Aktas O, Oksal BS and Kose EO. (2011). Essential oil composition and antibacterial activity of the grapefruit (Citrus Paradisi.L) peel essential oils obtained by solvent-free microwave extraction: comparison with hydrodistillation. International Journal of Food Science & Technology, 46: 1455–1461.
  17. Viuda-Martos M, Ruiz-Navajas Y, Fernandez-Lopez J. and Perez-Alvarez J. (2008). Antifungal activity of lemon (Citrus lemon), mandarin (Citrus reticulata L.), grapefruit (Citrus paradisi L.) and orange (Citrus sinensis L.) essential oils. Food Control 19: 1130- 1138.
  18. Carccioni DRL, Guizzardi M, Biondi DM, Renda A. and Ruberto G. (1998). Relationship between volatile components of citrus fruit essential oils and antimicrobial action on Penicillium digitatum and Penicillium italicum. International Journal of Food Microbiology 43: 73-79.
  19. Murase T, Misawa K, Haramizu S, Minegishi Y, Hase T.(2010). Nootkatone, a characteristic constituent of grapefruit, stimulates energy metabolism and prevents diet-induced obesity by activating AMPK. American Journal of Physiology Endocrinology and Metabolism. 299(2):E266-75.
  20. Harris B in “Phytotherapeutic uses of essential oils” in “Handbook of essential oils: science, technology and applications. (2010). Edited by K. Hüsnü Can Baser and Gerhard Buchbauer, CRC Press, p 336.
  21. Nagai K, Niijima A, Horii Y, Shen J, Tanida M. (2014). Olfactory stimulation with grapefruit and lavender oils change autonomic nerve activity and physiological function. Autonomic Neuroscience 185:29-35.