Published On: Wed, Nov 6th, 2013

Watermelon and orange: potent neutralisers of free radicals

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(By Temitope Obayendo)

  Some medicinal fruits and vegetables are said to owe their potency to the bitterness of their taste. But with the duo of watermelon and orange, it is a different ball game, as both contain sweet juices, with life-saving nutrients that can cure and prevent most common health disorders.

Scientists from the University of Benin and the Igbinedion University (both in Edo State) have conducted a research into the “Comparative evaluation of antioxidant effects of watermelon and orange, and their effects on some serum lipid profile of Wister albino rats.” Their findings were published in the International Journal of Nutrition and Metabolism Vol. 3(8).

In conducting the study, normal rats, given varying doses of the juices of the fruits were investigated. 120 g/70 kg body weight was used as the standard dose, while the animals were given the normal dose, × 1.5, and × 2.0 of the normal dose, orally, for a period of six weeks.

“Our findings showed that watermelon juice caused a dose-related decrease in SOD activity at weeks three and six, while orange juice caused a dose related increase in superoxide dismutase (SOD) activity,” the researchers said.

The result of the study further showed both catalase activities lower than that for control, and at high doses, both showed increased activity of catalase. Both juices caused a dose-related increase in HDL-cholesterol, with no significant difference between them. And watermelon caused a dose-related decrease in LDL-cholesterol, while orange caused a dose related increase in LDL-cholesterol.

But LDL concentration for orange treated test groups were shown to be higher than that for watermelon treated test groups. These show that both fruits are complimentary, as the shortcoming of one is made up for by the other. So, for full health benefit, it is better to consume both at the same time.

Nutritional Contents of Watermelon and Orange

Watermelon (Citrullus lanatus) is a member of the Cucumbitaceae family. It is an excellent source of the potent carotenoid antioxidant “lycopene”. This powerful antioxidant travels through the body neutralising free radicals. Other researchers have confirmed that a cup of watermelon provides 24.3 per cent of the daily value of vitamin C, and through its beta carotene, 11.1 per cent of the daily value of vitamin A.

The antioxidant function of lycopene is its ability to help protect cells and other structures in the body from oxygen damage and has been linked in human research to prevention of heart disease. Protection of DNA inside white blood cells has also been shown to be an antioxidant role of lycopene.

Before cholesterol can be deposited in the plaques that harden and narrow arteries, it must be oxidised by free radicals. With its powerful antioxidant activity, lycopene can prevent LDL-cholesterol from being oxidised.

Research indicates that diets low in carotenoids can increase the body’s susceptibility to damage from free radicals. As a result, over the long term, carotenoid-deficient diets may increase tissue damage from free radical activity, and increase risk of chronic diseases like heart disease and cancers.

Orange (Citrus sinensis) belongs to the genus citrus, of the family Rutaceae. It is a popular fresh fruit, often consumed because of its tangy taste and nutritive values. Oranges are rich in vitamin C and also provide some vitamin A. These vitamins serve as antioxidants, preventing the attack of free radicals on the cells of the body.

Orange is rich in a compound called liminoid, which combats cancer of the colon, stomach, breast, lung, skin, and mouth. Orange peels have alkaloid synephrine, which can cut down the production of cholesterol in the liver. The antioxidant elements in oranges combat oxidative stress that oxidises the LDL in the blood.

Oranges protect the skin from damage caused by free radicals, thus helping you look young and glowing.

The aqueous extract of Citrulus lanatus has been known to be a good source of glucose, fibre and also an excellent source of vitamin C, lycopene, and beta carotene. C. sinensis is also a good source of vitamin A and an excellent source of Vitamin C, Vitamin C being the major vitamin contained in both fruits.

Epidemiologically, it has been shown that antioxidants may reduce or inhibit the effect of oxidative stress in tissues and organs of the body. Vitamin C is a highly effective antioxidant, acting to lessen oxidative stress.

Stressing the health benefits of watermelon, the pioneer managing director/CEO of the Nigerian Medicinal Plants Development Company (NMPDC), Pharm. (Mrs) Zainab U. Shariff, said in an interview with pharmanews that every part of the watermelon is useful, bark, seed, and pulp. It contains 80 -90 per cent water, thus it is diuretic, rich in antioxidants and carotenoids from the red colour.

As an expert on herbs, she noted that watermelon with the combination of carrot, cucumber and a touch of ginger will produce an excellent natural fruit juice, which is very medicinal for diabetics, cancer patients, and for the general wellbeing of the human body.

“Watermelon serves as a cleanser because it cleanses and nourishes the kidney, thus, it’s suitable for diabetics. The availability of watermelon in most parts of the country makes its accessible to everyone,” she stated.

On the usefulness of the bark, she said the green bark is also very useful, in that, it can be dried and ground into powdery form, to be taken as tea in combination with orange, zobo and a little of ginger. “This bark is good for the liver because it has been established that it tones the kidney and liver,” she added.

Shariff, who is also the national chairman of the Association of Lady Pharmacists (ALPs) and a facilitator of the National Association of Nigerian Traditional Medicine Practitioners (NANTMP), explained that another way to use the bark of watermelon is to chop it, mix it with boiled water, sieve and drink.

According to her, “the seeds are believed to have aphrodisiac effects both on man and woman. One can chew seven to fourteen seeds daily, to experience the aphrodisiac effect, kidney flushing function, and erection improvement in men.”

Specific Health Benefits of Watermelon

  • Lowers blood pressure:

Watermelon contains a compound known as citrulline, which in the bloodstream, signals the body to release a compound that causes the blood vessels to dilate. As a result, blood flows through the vessels easily, causing less pressure on the vessel walls. According to a research, led by food scientists at The Florida State University, six weeks of L-citrulline extract from watermelon reduced blood pressure and aortic wave reflection in middle-aged individuals with pre-hypertension.

  • Boosts heart health, controls weight gain:

In a recent study, researchers at the Purdue University and University of Kentucky found that a diet including watermelon juice lowers weight, cholesterol and arterial plaque.

  • Protects from cancer:

Watermelon is rich in antioxidants such as lycopene which contains twice the amount found in tomatoes. Watermelon also contains vitamins C and A, which play active role in the fight against several cancers such as breast, prostate and colorectal cancer. Chinese study showed in 2009 that the compounds found in watermelon work to increase the programmed death in breast cancer cells.

  • Boosts libido and improves fertility:

Watermelon may have Viagra-like effect.  It is a rich source of amino acid citrulline, which works to further expand and relax the blood vessels, in a way similar to what happens when a man takes Viagra. This ensures the passage of more blood to the penis leading to erection.

  • Prevents heat stroke:

Watermelon is effective in reducing body temperature and blood pressure. Many people in the tropical regions eat the fruit to protect themselves from heat stroke.

  • Eases arthritis:

Watermelon can serve as a diuretic, which means that it can help to maintain the balance between fluids and glucose in the body. Aside from helping to keep the body hydrated, thereby helping to prevent arthritis, its rich beta-carotene and vitamin C content also contribute to reducing inflammatory processes associated with this disease.

  • Prevents constipation:

Drinking a big glass of watermelon juice is very effective in aiding the elimination of wastes. Consuming plenty of this red juice will do a lot of good.

  • Eases heartburn, morning sickness:

Watermelon eases heartburn and reduces swelling; its high water content (80-90 per cent) and fruit sugars alleviate morning sickness and dehydration; and the minerals it contains can help prevent third-trimester muscle cramps.

A 2003 study in the International Journal of Gynecology and Obstetrics found that daily lycopene supplements reduced the incidence of preeclampsia by 50 per cent. Test subjects were given four milligrammes of lycopene; a single serving of watermelon can increase that effect by three folds.

  • Avert infections:

Watermelon plays an important role in the prevention and treatment of many infections in the body.  As a rich source of vitamin C, it helps the body develop resistance against infectious agents and scavenge harmful oxygen-free radicals.

  • Sustains healthy kidneys:

Water melon contains a lot of potassium, which is very helpful in cleaning or washing off the toxic depositions in the kidneys. Moreover, it is helpful in reducing concentration of uric acid in the blood, thereby lowering the chances of kidney damages and formation of kidney stones in it.

In addition to helping to prevent dehydration due to its high water content, it induces frequent urinating, which is again helpful for cleaning of the kidneys.

2010 American Journal of Hypertension

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Watermelon and orange: potent neutralisers of free radicals