Antioxidant Properties Of Grape Skin

  • Megha PavangadMSc (Clinical Pharmacology), University of Glasgow, United Kingdom
  • Irenosen AddehMaster of Science (MSc), Public Health, University of Debrecen, Hungary

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Introduction

Antioxidants are substances that obstruct the oxidative damage mainly caused by free radicles in a living organism. It is essential to understand the importance of antioxidants. Antioxidants have anti-inflammatory and anti-ageing properties, which are proven to be very beneficial.

Nowadays, antioxidants are used in food technologies. Antioxidants are added to food to enhance food. Antioxidants are utilised to preserve and stabilise for various components found in food. Antioxidants' importance has been elevated by their use in pharmacology, cosmetics as well as medicine.

Regarding human health, antioxidants are against various damages caused by free radicals, which play a vital role in establishing several chronic diseases, including cardiovascular diseases, ageing, heart disease, anaemia, cancer, and inflammation.

Natural antioxidants present in food would prevent disruption, sourness, and change in the colour of the food. Red, orange, and purple-coloured fruits are rich in antioxidants. Oranges, lemons, blueberries, strawberries, and plums contain many antioxidants and must be incorporated into dietary menus. The important natural antioxidant vitamins include vitamin E and vitamin C.1

Grapefruit is considered a vital cultivar of the citrus genus that is considered containing various nutrients that would be beneficial to our health. It is considered that the fruits of the citrus genus are a source of compounds such as vitamins, carotenoids, fibre, and phenolic compounds that have various health benefits. Recently, it has been found that citrus fruit peels are the primary source of polyphenols and polymethoxylated Flavones.

These compounds have various therapeutic properties, including antiallergenic, anti-inflammatory, anti-microbial, anticarcinogenic, cardioprotective, antithrombotic, and vasodilatory effects. Both white and pink are recently gaining attention because of their nutritional and antioxidant properties.2

As a part of a balanced diet, it is essential to consume grapefruit, which directly contributes to antioxidant intake, which would help to improve human health. Grapefruits that contain antioxidants would help to reduce oxidative stress, reduce inflammation, and provide protection against various chronic conditions. 

Nutritional composition of grapefruit

  • Grapefruits are rich in organic acids, mainly citric acid (0.8-2 g/100ml)
  • Grapefruit contains Potassium, Magnesium, Vitamin C, and Flavonoids
  • 10% Potassium that is required daily, 6% in Magnesium, and 100% in Vitamin C are usually present in a glass of grapefruit juice3

Antioxidant compounds in grapefruit

Antioxidants present in grapefruit include: 

Naringin

A flavonoid glycoside naringin is present abundantly in the grapefruit skin and is the source of their bitterness. It is found that naringin might employ several therapeutic effects such as antioxidant and anticarcinogenic activity.4

Hesperidin

0.93 mg/ml of hesperidin is present in a grapefruit. It is known to have several therapeutic benefits such as anti-inflammatory, anti-microbial, ant-skin cancer, and skin-lightening activity.5 

Valencene

Valencene is present in grapefruit and is responsible for grapefruit fragrance.6 

Kaempferol

Kaempferol is found in a glycoside form in grapefruit, and it acts as a potent inhibitor of cytochrome P-450 metabolism.7

Vitamin C 

Grapefruits are considered to be a good source of vitamin C, an important antioxidant that protects cells from damage caused by free radicals.

Beta-carotene

Beta-carotene is found in the orange and pink varieties of grapefruit. Beta-carotene is considered a powerful antioxidant as it protects the cells from oxidative damage.

The mechanism of action of the antioxidants that are present in the grapefruit would involve the antioxidant’s ability to neutralise molecules that are considered being harmful in the body; these harmful molecules are known as free radicals. These free radicals are considered being highly reactive molecules that cause oxidative stress, which could result in cellular damage and damage to proteins and DNA.

Health benefits associated with grapefruit Antioxidants

  • Antioxidants in grapefruit help reduce oxidative stress, as oxidative stress could lead to cellular damage
  • Antioxidants present in grapefruit improve heart health by decreasing inflammation and improving cholesterol levels
  • Vitamin C, in grapefruit, plays a vital role in supporting the immune system
  • Antioxidants present in grapefruit play an important role in the prevention of certain types of cancer by neutralising free radicals that could cause DNA damage and contribute to the development of cancer cells
  • Antioxidants present in grapefruit protect the skin from damage that would be caused by free radicles, such as ageing and wrinkles
  • Grapefruits are beneficial for weight management
  • Antioxidants and the fibre present in grapefruit improve digestion

Factors influencing antioxidant content in grapefruit

Various factors can influence the antioxidant content in grapefruit: 

Varietal differences 

Various grapefruit varieties may have different levels of antioxidants. The genetic makeup also plays a vital role in determining its antioxidant content.

The chemical structure 

The antioxidant activity in grapefruits is related to their chemical structure. The flavonoid's structure and their antioxidant activity relationship are described in many studies. For instance, naringin, when compared to naringenin, has reduced radical scavenging efficiency. On the beta ring, the hydroxyl structure influences the radical scavenging efficiency of flavonoids. 

Pre-harvest factors

Various pre-harvest factors that influence the antioxidant activity in grapefruit include environmental conditions and agronomic conditions. The antioxidant activities are influenced by environmental conditions like moisture in the soil, temperature variation, radiation of sunshine, and various climatic conditions within a geographical location. The agronomic conditions influencing antioxidant activity include fertiliser, sowing date, irrigation, maturity stages, and subsequent harvesting.

Post-harvest factors

The main factor that influences antioxidant activity includes the Post-harvest factors. The post-harvest factors include storage conditions, such as time, temperature, humidity, light intensity, and agrochemicals. The gas composition also influences antioxidant activity.

Processing factors

Cans, juices, wines, vinegar, jams, and preserves are the various products grapefruits could be processed into. Processing methods include heat treatments such as canning and blanching, as well as non-heat treatments such as high-pressure processing. These processing methods can influence antioxidant activity in grapefruit.8 

Recommended dietary intake of grapefruit for antioxidant benefits

  • Half of a medium-sized grapefruit should be served. One to two servings of grapefruit should be consumed in a day
  • A variety of fruits and vegetables are to be included in your diet to ensure a diverse range of antioxidants and other nutrients. Grapefruit can be a part of this variety
  • Grapefruit is considered a healthy addition to your diet, but it's essential to balance your intake with other nutrient-rich food. A variety of fruits, vegetables, whole grains, lean proteins, and healthy fats are to be incorporated into your diet for balanced nutrition
  • Grapefruit consumption needs to be limited to specific individuals who have certain health conditions or are taking certain medications. Grapefruit tends to interact with certain medications, so it is necessary to consult your physician
  • Fresh grapefruits are preferred over processed forms such as canned or juices, as they may contain added sugar and reduced antioxidants
  • Organic grapefruits are chosen as they may have reduced exposure to pesticides and other contaminants
  • Various antioxidants such as vitamin C, flavanoids, and carotenoids are present in grapefruit. A variety of antioxidant-rich foods needs to be consumed to be healthy
  • Grapefruit does have various antioxidant benefits, excessive consumption may result in side effects, especially in individuals who have certain health conditions

It is good to incorporate grapefruits into your diet. In case of certain health conditions, it is best to consult your doctor before consumption of grapefruit.

FAQs

What does grape skin do for you?

Grapefruits are thought to have anti-inflammatory and antioxidant properties.

Does grape skin have polyphenols?

Anthocyanins, Flavanols, and Resveratrol are important polyphenols in grapefruit.

What are the benefits of grape skin extract?

Grape skin extract helps in cholesterol management,maintains health, antioxidant and anti-inflammatory support to the brain, and helps to manage a healthy blood sugar level.

How much resveratrol is in grape skin?

50-100 micrograms/grams of resveratrol is present in grape skin.

Summary 

Antioxidants are substances that obstruct the oxidative damage mainly caused by free radicles in a living organism. Antioxidants have anti-inflammatory and anti-ageing properties, that have proven to be very beneficial. Grapefruit is considered being a vital cultivar of the citrus genus, and it contains various nutrients that are beneficial to our health.

It is considered that the fruits of the citrus genus are a source of compounds such as vitamins, carotenoids, fibre, and phenolic compounds that have various health benefits. Recently, it has been found that citrus fruit peels are the primary source of polyphenols and polymethoxylated Flavones.

These compounds have various therapeutic properties, including antiallergenic, anti-inflammatory, anti-microbial, anticarcinogenic, cardioprotective, antithrombotic, and vasodilatory effects. Both white and pink are recently gaining attention because of their nutritional and antioxidant properties. 

Various antioxidants in grapefruit include naringin, hesperidin, valencene, kaempferol, vitamin C, and beta-carotene. Various factors influencing antioxidant content in grapefruit include Varietal Differences, The Chemical Structure, Pre-Harvest Factors, Post-Harvest Factors, and Processing Factors.

As a part of a balanced diet, it is essential to consume grapefruit, which directly contributes to antioxidant intake, which would help to improve human health. Grapefruits that contain antioxidants would help to reduce oxidative stress, reduce inflammation, and provide protection against various chronic conditions.

References

  1. Zehiroglu C, Ozturk Sarikaya SB. The importance of antioxidants and place in today’s scientific and technological studies. J Food Sci Technol [Internet]. 2019 Nov [cited 2024 Jan 23];56(11):4757–74. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6828919/
  2. Castro-Vazquez L, Alañón ME, Rodríguez-Robledo V, Pérez-Coello MS, Hermosín-Gutierrez I, Díaz-Maroto MC, et al. Bioactive flavonoids, antioxidant behaviour, and cytoprotective effects of dried grapefruit peels(Citrus paradisi Macf.). Oxid Med Cell Longev [Internet]. 2016 [cited 2024 Jan 23];2016:8915729. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4745316/
  3. Ivanova NN, Khomich LM, Perova IB, Eller KI. [Grapefruit juice nutritional profile]. Vopr Pitan. 2018;87(5):85–94.
  4. Naringin - an overview | sciencedirect topics [Internet]. [cited 2024 Jan 25]. Available from: https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/naringin#:~:text=Naringin%20is%20a%20flavonoid%20glycoside,the%20origin%20o
  5. Man MQ, Yang B, Elias PM. Benefits of hesperidin for cutaneous functions. Evid Based Complement Alternat Med [Internet]. 2019 Apr 2 [cited 2024 Jan 25];2019:2676307. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6466919/
  6. Valencene - an overview | sciencedirect topics [Internet]. [cited 2024 Jan 25]. Available from: https://www.sciencedirect.com/topics/neuroscience/valencene
  7. Schubert W, Eriksson U, Edgar B, Cullberg G, Hedner T. Flavonoids in grapefruit juice inhibit the in vitro hepatic metabolism of 17 beta-estradiol. Eur J Drug Metab Pharmacokinet. 1995;20(3):219–24.
  8. Zou Z, Xi W, Hu Y, Nie C, Zhou Z. Antioxidant activity of Citrus fruits. Food Chemistry [Internet]. 2016 Apr 1 [cited 2024 Jan 27];196:885–96. Available from: https://www.sciencedirect.com/science/article/pii/S0308814615014156
  9. Xia EQ, Deng GF, Guo YJ, Li HB. Biological activities of polyphenols from grapes. Int J Mol Sci. 2010 Feb 4;11(2):622–46.

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Megha Pavangad

MSc (Clinical Pharmacology), University of Glasgow, United Kingdom

I am a recent Msc in Clinical Pharmacology graduate from the University of Glasgow with a strong interest in Medical Writing. I have an experience as a Clinical Pharmacist Intern.

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