The magic of sweet oranges

If you were to compare apples and oranges and find them to be the same, you would be talking about Citrus sinensis– the sweet orange. After all, this popular fruit is called ‘sinaasappel’ in Dutch and ‘apfelsin’ in a Germanic dialect, both translating to Chinese apple. Even the Italians and the French went through a phase of calling the orange ‘melarancia’ – a combination of ‘melas’ (apple) and ‘naranja’ (Arabic for orange). Somewhere the apple got dropped and the English name remains as ‘orange’, derived from the Sanskrit ‘naranga’ indicating its Indian origin 1. While the origins of the fruit are still unknown, it is clear that this fruit has been coveted since millennia.

Popular the world over, the sweet orange needs no introduction. The fruit pulp and juice is consumed in industrial quantities thanks to pasteurisation, packaging and transportation. Little attention, however, is paid to the peel that comes off so easily and at best, is made into candied confectionary. So while most swear by the medicinal value of vitamin C-rich orange juice, the benefit of the essential oil from the peel is largely tossed into the dustbin. Now, with a renewed interest in essential oils beyond aromatherapy, orange essential oil has quietly risen in the estimate of cosmetologists and scientists. And because of its positive effect on skin, the oil of Citrus sinensis is an important ingredient in griffin + row’s Cleanse and Nourish formulations.

Introducing Citrus sinesis

Citrus sinensis is commonly referred to as sweet orange to differentiate it from Citrus aurantium or the bitter orange. The fruit is thought to be a hybrid of the pomelo (Citrus grandi) and the Mandarin orange (Citrus reticulata) 2. Botanically, it is also called Citrus aurantium var. dulcis or Citrus aurantium var. sinensis referring to the sweetness of the pulp and its Chinese origin, respectively.

The fruit is indigenous to Southern China, Vietnam, North-eastern and Eastern India. The earliest introduction of the fruit to the western hemisphere must have been by Roman traders whose business interests lay in south-eastern India 3. This would explain why the Italians call the fruit ‘aranje’ (derived from the Sanskrit ‘naranga’). From Italy, the orange rolled into southern France and became the ‘oranje’ and finally the English ‘orange’. Later, in the 1500s, Portuguese traders who sought to buy spices from southern India took the orange to South-western Europe – Spain and finally Greece. For that, the Greeks named the fruit as ‘portucallis” meaning ‘That which was brought by the Portuguese’. This crossed over to Turkey and found its way to the Middle East to become the ‘bortukalla3.

Orange seeds were brought to the New World by Christopher Columbus, in 1493, on his second voyage. Thus Haiti and San Salvadore were introduced to cultivation of the first orange trees. The Spanish explorer Ponce de Leon introduced the fruit to Florida in St. Augustine. Spanish missionaries then brought the same to Texas 4. Portuguese settlers in South America started orange cultivation in some of their colonies there.

Today, Brazil tops the list of orange-exporting countries, followed by the USA, China and India and Mexico. The sweet orange cultivated today has several subspecies such as the blood orange (which has a reddish coloured pulp), navel orange (which has a distinct depression at the bottom with the emergence of an incompletely formed fruit) and the Valencia orange.

Traditional uses of Citrus sinensis

The orange has enjoyed a prominent place in the food preparations of Chinese and the Indian sub-continent. Although there are claims that the Vedas written in 7000 BC mention the ‘naranga’ or orange, it is possible that the same refers to a citrus fruit that is not necessarily the sweet orange 5.

Orange as a fruit:

The cultivation of orange dates back to 2500 BC in China, where orange orchards were established to avoid foraging for the fruit in the forests. Selective hybridisation yielded produce of increasing sweetness in order to please the reigning monarch. The fruit was a delicacy and appreciated purely for its taste 3.

Once the orange was known to the Romans, cultivation commenced with orchards established as far as Tunisia and Morocco. One of the remnants of these ancient orchards can still be seen in the small public park called Giardino degli Aranci (the Garden of Oranges) next to the Santa Sabina monastery on the Aventine Hill in Rome 6. Interestingly, this monastery is built close to a pagan temple to Juno, whose Greek counterpart- Hera – presented Zeus with golden fruit at their wedding. The legend of Heracles also mentions the trees of golden fruit being guarded by the Hesperides in a garden at the foot of the Atlas Mountains (in Morocco) indicating that the warmer countries in the Mediterranean also cherished the fruit. All these stories mention a highly coveted ‘golden fruit’ which could either be the orange or just quince. However, for some strange reason Roman orange orchards died out and Greece completely missed out on the sweet orange when it first journeyed out of the Indian sub-continent.

When the Portuguese re-introduced the orange to southern Europe, it quickly regained popularity and ‘Orangeries’ sprang up all over the Mediterranean. At the same time, the Dutch East India Company may have stumbled upon to the orange in the Malay Peninsula. And while the country is too cold for the cultivation of the orange, the Dutch still refer to the fruit as ‘Chinese apple’.   

The first mention of the medicinal properties of the orange comes from certain Indian texts on traditional medicine as late as the 14th– 15th century. The Madanapala Nighantu, for example, describes the use of the ‘naranga’ as a purgative, laxative and general heart tonic 5

Orange blossoms:

The orange blossom often coexists with the fruit. This was held by the ancient Chinese to be a symbol of chastity and purity. Young Chinese brides wore orange blossom on their wedding day. This practice reached Europe after the Crusades and young men returning from war often brought back orange blossom for their brides. When Queen Victoria herself wore orange blossom on her wedding day, it became de rigeur for all English brides to do the same 7.

Orange blossom was used as a medicine in China and Malaya while the Spanish used dried flowers in tea. Orange blossom water was perhaps the earliest perfumed water to be used in the Middle Ages in Europe 8

Orange juice:

Traditionally, orange pulp was preserved as marmalade. However, the cultivation of oranges on a large scale in the US led to a glut in the produce in the early 1900s. This led Albert Lasker to first exploit the excess by introducing the process of pasteurisation (which had earlier been applied only to wine) and packaging the juice as the famous ‘Sunkist’ brand 2. This opened up new avenues of marketing and introduced the fruit to remote places.

Orange essential oil: 

The use of the essential oil from orange peel appears to be quite recent. Perhaps the properties of the oil were exploited only after the technique of steam distillation to collect essential oils developed by Ibn Sina –the great Arabic physician- was applied to the orange. The earliest use of the oil appears to be as an insect repellent. Nevertheless, orange essential oil now occupies an important place in aromatherapy.   

Orange peel:

Orange peel has a history of culinary use. The zest of the fruit was added to preparations for its tanginess. Candied peel is added to baked confections and ice-cream.  Orange peel was also rubbed on acne-affected skin to decrease scarring 8. Peel extracts are now used in cosmetic products as binders, emulsion stabilisers and to adjust the viscosity of a formulation 9.

Orange wood:

Wood from orange trees is used to make small furniture items.

Bioactivity and associated components of the plant

The orange tree is versatile in that almost every part of it has some use. As far as bioactivity goes, the fruit pulp is a repository of citric acid, vitamins A, C and B (folate, thiamine and pyridoxine). The leaves contain an essential oil that has a large quantity of the terpene sabinene. Even the seed contains a minute quantity of oil rich in antioxidants 10.

Orange essential oil refers to the liquid extracted from the fruit peel. A total of 18-22 compounds are identified from the essential oil of the peel. The main constituents are 11

Monoterpenes: Limonene, β-myrcene, α-pinene

Oxygenated monoterpenes: Linalool and isophorone

Sesquiterpenes: Valencene

Terpene aldehydes: α-Sinensal and β-Sinensal.

Valencene and sinensals: a spotlight on the main bioactive components

  • Valencene is a sesquiterpene.  

Valencene is responsible for the woody undertones of the orange fragrance and flavour. While the synthetic pathway of sesquiterpenes terminates with this molecule in oranges, it is further converted to nootkatone in the grapefruit. Both valencene and nootkatone are thought to be important for seed-dispersal in that they act as attractants for frugivorous creatures 12.

  • α- sinensal is a terpene aldehyde.  

α- Sinensal (and its isomer β- sinensal) are signature molecules present in the essential oil of Citrus sinensis. They contribute to the overall fragrance of sweet orange oil 13

General health benefits and uses of sweet orange oil:

Orange essential oil is extracted from the rind of the ripe fruit. It is important that the rind is not dry, since there could be some changes in the composition of the oil extracted. Cold pressing of the sliced rind yields a yellow coloured, non-viscous oil 14.

Like most citrus oils, orange essential oil is added to carrier oils and used sparingly in formulations that are used on skin exposed to UV rays (sunlight). Mild irritation may be experienced due to the phototoxic degradation of one or more compounds in the oil.

The main use of orange essential oil is in cosmetics and in aromatherapy.  

Use in the cosmetic industry: Orange essential oil is incorporated into skin care formulations for its detoxifying effect on skin. While it can soothe dry or inflamed skin, there is empirical evidence to show that it boosts collagen formation leading to clear and younger looking skin 14.

Aromatherapy: Orange essential oil has a light, uplifting and refreshing fragrance. It is recommended for use to dispel negative emotions and to enhance a convivial atmosphere when diffused.  Stress-induced immunosuppression has also been relieved with the help of orange essential oil 15. It has also been used to treat insomnia 16.

Scientifically, orange essential oil has been proven to have the following properties-

  • Anti-acne: Gel-based formulations with a mixture of essential oils including Citrus sinensis oil showed a marked improvement in complexion of volunteers with acne. The formulations made with acetic acid showed both keratolytic and anti-microbial effects resulting in a visible decrease in acne and acne scars 17.
  • Antibacterial activity: In vitro studies have demonstrated a significant bactericidal activity of orange essential oil against Staphylococcus aureus (a normal skin bacterium that can promote the formation of pimples), coli, Pseudomonas aeruginosa and Listeria monocytogenes. 18
  • Anti-fungal activity: Antimycotic activity of orange essential oil has been demonstrated for several fungi and yeast including Candida albicans which is known to aggravate dandruff 18.
  • Anti-parasitic activity: Extracts of orange essential oil in organic solvents such as ethyl acetate and chloroform have been shown to be detrimental to Plasmodium falciparum, Trypanosoma brucei and Trypanosoma evansi 18.
  • Anticancer activity: The anticancer action of orange essential oil is presumed to be due to perillyl alcohol which is derived from limonene. This activity, however, has been demonstrated only in laboratory animals 19.
  • Antiarthritic action: Massage of affected joints with a mixture of ginger and sweet orange oils has been shown to give relief to arthritic joint pain 20.

Insecticidal activity: Like all citrus oils, the limonene content of orange essential oil makes it a natural and effective insect repellent 18.

Use in the food industry: Orange essential oil is added to enhance the flavour of foods and beverages.

Botany and grow it yourself

The orange tree belongs to the Citrus family of Rutaceae. This shallow-rooted tree can grow to a height of about 20 ft. The trunk and branches have spines. The leaves are dark green and glossy, with the typical winged petiole of the citrus fruits. The flowers are attractive, five-petalled and white in colour, often co-existing with the fruit. The fruit is spherical and has an epicarp that can be easily separated from the thin, white coloured and bitter mesocarp. The pericarp is segmented and individual sacs are filled with orange juice that is rich in vitamins and citric acid.
The orange tree can be grown from seeds although grafting with root-saplings is more popular. Calcareous, semi-alluvial soils are preferred for cultivation and irrigation is mandatory under conditions of low rainfall. Semi-tropical climate is best for the growth of oranges, since temperatures below 0°C causes the juice in the fruit to freeze and subsequent death of the fruit.
Orange trees can be cultivated in large tubs due to their non-penetrating roots. However, the width of the tub should allow the proper growth of the roots that can spread over a considerable area.
The trees begin to bear fruit after about 2-3 years. The fruit must be allowed to ripen on the tree although residual greenness in the epicarp can be removed by exposure to ethylene. Care should be taken while harvesting the fruit since shaking the tree can release several allergens that can result in skin rashes 8

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. Valencene has three isoprene units and is a sesquiterpene.

Flavonoids: Flavonoids are a subclass of polyphenols that have two six-membered carbon rings and an 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. Hesperidin is a flavonoid present in citrus fruits.

Immunosuppression: A phenomenon where the body’s immune system is prevented from working optimally by external factors (such as stress) or infections (such as HIV).

Keratinolytic: A compound that helps to break down keratin. In the healing process, the deposition of excess keratin can lead to thick scar formation. Keratinolytes not only help to hasten the healing process, but also reduce scarring by dissolving excess keratin.

Frugivorous: Fruit-eating. Most bats are frugivorous mammals.


References

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