Introduction and description
Watermelon (Citrullus lanatus var. lanatus, family Cucurbitaceae) is a vine-like (scrambler and trailer) flowering plant originally from southern Africa.
It is a large, sprawling annual plant with coarse, hairy pinnately-lobed leaves and white to yellow flowers. It is grown for its edible fruit, also known as a watermelon, which is a special kind of berry referred to by botanists as a pepo. The fruit has a smooth hard rind, usually green with dark green stripes or yellow spots, and a juicy, sweet interior flesh, usually deep red to pink, but sometimes orange, yellow, or white, with many seeds.
The watermelon is thought to have originated in southern Africa, where it is found growing wild. It reaches maximum genetic diversity there, with sweet, bland and bitter forms.
In the 19th century, Alphonse de Candolle considered the watermelon to be indigenous to tropical Africa. Citrullus colocynthis is often considered to be a wild ancestor of the watermelon and is now found native in north and west Africa.
Evidence of its cultivation in the Nile Valley has been found from the second millennium BC onward. Watermelon seeds have been found at Twelfth Dynasty sites and in the tomb of Pharaoh Tutankhamun. Watermelon is also mentioned in the Bible as a food eaten by the ancient Israelites while they were in bondage in Egypt.
In the 7th century, watermelons were being cultivated in India and by the 10th century had reached China, which is today the world's single largest watermelon producer.
Moorish invaders introduced the fruit into Europe and there is evidence of it being cultivated in Córdoba in 961 and also in Seville in 1158.
It spread northwards through southern Europe, perhaps limited in its advance by summer temperatures being insufficient for good yields.
The fruit had begun appearing in European herbals by 1600, and was widely planted in Europe in the 17th century as a minor garden crop.
European colonists and slaves from Africa introduced the watermelon into the New World. Spanish settlers were growing it in Florida in 1576, and it was being grown in Massachusetts by 1629, and by 1650 was being cultivated in Peru, Brazil and Panama as well as in many British and Dutch colonies. Around the same time, Native Americans were cultivating the crop in the Mississippi valley and Florida. Watermelons were rapidly accepted in Hawaii and other Pacific islands when they were introduced there by explorers such as Captain James Cook.
What is fascinating about the history of the watermelon from that point on is that selective breeding has changed the nutritional value of subsequent varieties.
The old strains of water melon are said to be rich in Vitamins A and C, minerals, and contain malic acid, an important chelating agent. The new varieties do not seem to be the same.
Much research effort has been devoted in the USA to breeding disease-resistant varieties with large yields, and into developing a seedless strain or at least a breed with less seeds. The result, if we glance at the chart below produced by Dr Duke – who is USA based – is a water melon with no malic acid and no Vitamin C. In fact its Vitamin content is quite low. Nowadays a large number of cultivars are available in the USA, many of them producing mature fruit within 100 days of planting the crop. It appears however, that nutritionally, the resulting fruit is inferior to that produced elsewhere.
The breeding programmes introduced by American horticulturists appear to have been based almost entirely on the demands of the growers - yield and ease of shipment and storage.
Charles Fredric Andrus, for example, a horticulturist at the USDA Vegetable Breeding Laboratory in Charleston, South Carolina in 1954, bred "that gray melon from Charleston". Its oblong shape and hard rind made it easy to stack and ship. Its adaptability meant it could be grown over a wide geographical area. It produced high yields and was resistant to the most serious watermelon diseases. What it tasted like and nutritionally how it fared is not reported.
Subsequent programmes based on hybridisation were also based on “ higher yields, and attractive appearance”. Again not taste or nutritional value. Today, farmers in approximately 44 states in the United States grow watermelon commercially. Georgia, Florida, Texas, California and Arizona are the United States' largest watermelon producers. This now-common fruit is often so large that groceries in the USA often sell half or quarter melons. The largest recorded fruit was grown in Tennessee in 2013 and weighed 159 kilograms (350.5 lbs).
The table below shows the contents of the fruit and seeds.
The information comes from Dr Duke’s Plant database. Where a chemical has no recorded activity it is excluded from the following list. Dr Duke’s database should be referenced for more and up-to-date details.
Minerals are shown in BLUE. The ones not present in the fruit are:
- Iodine and
Vitamins are shown in GREEN. Some essential vitamins are present in the fruit, but many are absent
- vitamin B7 also known as biotin is not present.
- vitamin B12 also known as cobalamin is not present
- vitamin D also known as ergocalciferol is not present.
- vitamin E also known as tocopherol is not present.
- vitamin K is also known as naphthoquinoids is not present
Fatty acids - Two fatty acids are essential for human beings – ALA and LA – and only LA is present. Shown as PINK
Essential amino acids - and conditionally essential amino acids are shown in YELLOW. The fruit is very rich in Eaas. The only EAA not present in the fruit is Proline. But, Hydroxyproline is present, an amino acid which is normally produced in the body by hydroxylation of the amino acid proline. Hydroxyproline comprises roughly 4% of all amino acids found in animal tissue, an amount greater than seven other amino acids that are translationally incorporated and Hydroxyproline is a major component of the protein collagen. Both Hydroxyproline and proline play key roles for collagen stability. Collagen, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendons, ligaments and skin. It is also abundant in corneas, cartilage, bones, blood vessels, the gut, intervertebral discs and the dentin in teeth. In effect it is an essential body repair and building substance.
Other interesting chemicals – Dr Duke identified a number of chemicals which, at the time of writing did not have an identified activity, though clearly they have a purpose, it is just that the purpose is not yet known. Other interesting chemicals besides these include:
- Boron - The presence of Boron in this sample looks like an anomaly, and may indicate a metal chelating capability.
- Citrulline - The organic compound citrulline is an α-amino acid. Its name is derived from citrullus, the Latin word for watermelon, from which it was first isolated in 1914 by Koga & Odake. It is a key intermediate in the urea cycle, the pathway by which mammals excrete ammonia. In the body, citrulline is produced as a byproduct of the enzymatic production of nitric oxide from the amino acid arginine, catalyzed by nitric oxide synthase. This is an essential reaction in the body because nitric oxide is an important vasodilator required for regulating blood pressure. As Wikipedia so delicately puts it, the vasodilation helps in “relaxing smooth muscle in blood vessels and erectile organs”. In effect it may help with erectile dysfunction.
- Lycopene – gives the fruit its lovely colour. It is a bright red carotene and carotenoid pigment and phytochemical found in tomatoes and other red fruits and vegetables, such as red carrots, and papayas, although not in strawberries, red bell peppers, or cherries. Although lycopene is chemically a carotene, it has no vitamin A activity
- Serine - is important in our metabolism. It plays an important role in the catalytic function of many enzymes. It is worth mentioning that a number of insecticides interfere with this catalytic function by combining with serine ‘in the active site of acetylcholine esterase’, inhibiting the enzyme completely, which is why insecticides cause our metabolisms to go haywire.
- Phytosterols, which encompass plant sterols and stanols, are steroid compounds similar to cholesterol which occur in plants and vary only in carbon side chains and/or presence or absence of a double bond. They are essential cell repair substances like cholesterol
Information is also provided for the seeds, which one would normally spit out. And it appears that it is a good idea to spit them out, in the USA at least, for in any large quantities they would end up being slightly poisonous. The seeds contain a number of chemicals designed to protect them from insects, fungus and other pests, but as a consequence they would be irritant if consumed in quantity.
CAPRIC-ACID and CAPRYLIC-ACID, for example, which are only in the seed are Fungicides and Pesticides; LAURIC-ACID found in the seed fights bacteria and viruses; MYRISTIC-ACID again found only in the seed fights parasites. There is no evidence that they have this ability in us, so take care.
Chemicals and their Biological Activities in: Citrullus lanatus (THUNB.) MATSUM. & NAKAI (Cucurbitaceae) -- Watermelon
ALANINE Fruit 2,000 ppm; Seed 15,000 ppm;
ARGININE Fruit 6,949 ppm; Seed 46,600 ppm;
ASPARTIC-ACID Fruit 4,594 ppm; Seed 25,500 ppm;
BETA-CAROTENE [Vitamin A] Fruit 2 - 48 ppm
BORON Fruit 1 - 4 ppm
CALCIUM Fruit 100 - 3,400 ppm Seed 1,294 - 1,300 ppm
CAPRIC-ACID Seed 2,200 - 4,840 ppm
CAPRYLIC-ACID Seed 400 - 880 ppm
CARBOHYDRATES Fruit 3,800 - 859,000 ppm Seed 44,000 - 48,000 ppm
CITRULLINE Fruit 1,627 ppm;
COPPER Fruit 4 ppm;
CUCURBITACIN-E Fruit: Leaf:
CYSTEINE Fruit 236 ppm; Seed 5,742 ppm;
FAT Fruit 200 - 89,000 ppm Seed 200,000 - 571,000 ppm
FIBER Fruit 35,300 - 257,000 ppm Seed 67,000 - 316,000 ppm
FOLACIN Fruit 0.259 ppm; vitamin B9 also known as folic acid or folate
GLUTAMIC-ACID Fruit 7,420 ppm; Seed 53,000 ppm;
GLYCINE Fruit 1,178 ppm;
HISTIDINE Fruit 707 ppm; Seed 7,018 ppm;
IRON Fruit 2 - 143 ppm Seed 75 ppm;
ISOLEUCINE Fruit 2,238 ppm; Seed 12,100 ppm;
LAURIC-ACID Seed 1,600 - 3,250 ppm
LEUCINE Fruit 2,120 ppm; Seed 21,100 ppm;
LINOLEIC-ACID Seed 52,000 - 210,280 ppm
LUTEIN Fruit 0.14 - 3 ppm
LYCOPENE Fruit 45 - 900 ppm
LYSINE Fruit 7,303 ppm; Seed 8,932 ppm;
MAGNESIUM Fruit 1,081 - 1,500 ppm
MANGANESE Fruit 4 ppm;
METHIONINE Fruit 707 ppm; Seed 5,742 ppm;
MYRISTIC-ACID Seed 400 - 800 ppm
NIACIN [Vitamin B3] Fruit 15 - 27 ppm
OLEIC-ACID Seed 71,000 - 189,000 ppm
PALMITIC-ACID Seed 15,200 - 55,000 ppm
PANTOTHENIC-ACID [vitamin B5 ] Fruit 25 ppm;
PHENYLALANINE Fruit 1,767 ppm; Seed 16,600 ppm;
PHOSPHORUS Fruit 1 - 2,900 ppm Seed 8,300 - 14,600 ppm
PHYTOSTEROLS Fruit 236 ppm;
POTASSIUM Fruit 13,514 - 18,000 ppm
PROTEIN Fruit 1,000 - 100,000 ppm Seed 198,000 - 343,000 ppm
RIBOFLAVIN Vitamin B2 ] Fruit 2 - 8 ppm Seed 1 ppm;
SERINE Fruit 1,885 ppm; Seed 13,700 ppm;
SODIUM Fruit 135 - 236 ppm
STEARIC-ACID Seed 12,200 - 66,000 ppm
THIAMIN [Vitamin B1] Fruit 4 - 9 ppm
THREONINE Fruit 3,180 ppm; Seed 15,300 ppm;
TRYPTOPHAN Fruit 825 ppm;
TYROSINE Fruit 1,413 ppm; Seed 10,200 ppm;
VALINE Fruit 1,885 ppm; Seed 10,200 ppm;
WATER Fruit 915,100 - 957,000 ppm Seed 71,000 - 81,000 ppm
ZINC Fruit 8 ppm;
Watermelon is one fruit that can simply be consumed as it is, although watermelon sorbet is delicious, particularly if made with grenadine syrup as a sweetener. Crushed it also makes a very pleasant refreshing drink.
Some older variety Watermelon rinds are also edible, they are stewed, stir fried and are used for making pickles..
And people consume the seeds.
This has again led us to wonder whether the breed of watermelon produced in the USA has seeds different in composition to those in countries where the older breeds are still used.
Certainly, in China there are no reports of people suffering from consumption of the seeds and they are eaten like almonds, being consumed with other seeds at Chinese New Year celebrations.
Speculatively, has the reduction in the number of seeds in USA water melons resulted in the concentration by the plant of the more toxic elements into the few remaining seeds in order that the small number of seeds that remain, remain viable?
Watermelon juice can be made into wine, on its own or blended with other fruits.
- Dr Duke's list of Chemicals and their Biological Activities in: Citrullus lanatus (THUNB.) MATSUM. & NAKAI (Cucurbitaceae) -- Watermelon 019288
- Dr Duke's list of Plants containing ARGININE 017958
- Dr Duke's list of Plants containing GLYCINE 017955
- Dr Duke's list of Plants containing HISTIDINE 019061
- Dr Duke's list of Plants Containing HYDROXYPROLINE 017965
- Dr Duke's list of Plants containing LUTEIN 018922
- Dr Duke's list of Plants containing LYSINE 017957
- Dr Duke's list of Plants containing PHENYLALANINE 017936
- Dr Duke's list of Plants containing PROLINE 017956
- Dr Duke's list of Plants with AntiAddisonian Activity 018405
- Dr Duke's list of plants with AntiADHD activity 018403
- Dr Duke's list of Plants with Antibiotic activity 018353
- Dr Duke's list of Plants with Anticancer (bladder) activity 018452
- Dr Duke's list of Plants with Anticancer (prostate) activity 018465
- Malic acid as a chelating agent 006176
- Omega-3 and omega-6 content of medicinal foods for depressed patients: implications from the Iranian Traditional Medicine 017018