Pakuan is a spreading,
hairy, tendril-bearing annual vine reaching a length of several meters. Leaves are long-stalked,
oblong-ovate, 8 to 20 centimeters long, deeply 3- to 7-lobed, pinnatifid
with usually narrowed segments. Flowers are monoecious, yellow, and
about 2 centimeters in diameter, occurring singly in axils of the leaves.
Fruit is very large, smooth, ellipsoid to oblong, light green with
irregular dark green-mottled stripes, sometimes covered with a white, waxy bloom, about 30 centimeters long. The flesh
is white, yellowish, pink or red; crisp, soft and juicy. Seeds
are compressed, sometimes red, usually black.
- Widely cultivated
in the Philippines.
- Fruit extract yielded carbohydrates, proteins, amino acids, steroids, glycosides, flavonoids, tannins and polyphenols.
- The skin contains
a fixed oil, arachidic acid, and traces of copper.
The seeds contain oil, 15 to 45%, made up of glycerides of linoleic
acid, oleic acid and palmitic and stearic acids. The oil contains
a small amount of phytosterol.
- A study suggests the active principle in the seed is a glucoside-saponin
- Flesh of fruit contains saccharose, dextrose, levulose, invert sugar, citrullin, lycopin, carotin, etc.
- All parts of the watermelon - rind, flesh, and seeds - contain citrulline, a non-essential amino acid, which converts to L-arginine when eaten.
- Seeds are a rich source of enzyme urease.
- Unsaturated fatty acid content of an ether extract in water melon seeds was reported at 76.1%, mainly linoleic acid.
- A 1967 study isolated a new amino acid from the pressed juice of Citrullus vulgaris and named p-(pyrazolyl-N)-alanine on the basis of its nuclear magnetic resonance spectrum and other properties. (25)
- Study of vine yielded ten compounds:
pentadecanoic acid, monopentadecanoin, 2, 3-dihydroxypropyl nonadecoate, lignoceric acid-2, 3-dihydroxy-propanenyl ester, lancerebroside 5, salicylic acid, 4-hydroxybenzoic acid, hydroquinone, succinic acid and vanillic acid. (15)
- Alcoholic and aqueous extracts revealed the presence of carbohydrates, proteins, flavonoids, saponins, fixed oils, glycosides and steroids. (See study below) (18)
- Physiochemical composition yielded moisture 19.21%, ash content 2.85%, acid soluble 2.105%, acid insoluble 1.00%, fibre content 13.67%, oil content 35.2%, iodine value 179.0, acid value 148.0,
invert sugar 39.95%. (19)
- Analysis of fatty acid profile of seed oil confirmed the presence of palmitic, stearic, oleic, linoleic, and linoleic acids, with linoleic acid being the most abundant of the five. Physiochemical characteristics of seed oil showed a saponification value of 132.33 mgKOH/g, acid value 06.48KOH/g, peroxide value 21 Meq/kg, iodine value 123 gI2/100g, specific gravity 0.915, refractive index 1.46. (22)
- Macronutrient profile (per 1 cup diced watermelon [approx. 152 g]): 45 calories, 1 g protein, 11.5 g carbohydrate, 0.2 g fat. Watermelon is an excellent source of vitamin C 12.3 mg (20.5% DV), vitamin A 865 IU (17.3% DV); a very good source of potassium 170 mg (4.9%DV). Other minerals and vitamins are magnesium 15 mg (3.8% DV), vitamin B6 0.07 mg (3.5% DV), vitamin V1 0.05 mg (3.3% DV), vitamin E 0.08 mg (3% DV), manganese 0.06 mg (3% DV), dietary fiber 0.6 g (2.4% DV), iron 0.4 mg (2.2% DV), phosphorus 17 mg (1.7% DV), folate 5 mcg (1.3% DV), and calcium 11 mg (1.1% DV). (DV is daily value based on a 2,000 calorie diet, as established by USFDA) (26)
- Seeds considered cooling, demulcent, diuretic, vermifuge, nutritive, pectoral and pectic.
- The crude extract of seeds believed to have a lowering blood
Seeds, fruit, roots.
Edibility / Nutrition
- Widely eaten in the Philippines.
Not high in nutritive value; only a fair source of calcium and iron.
- Seeds are oily; sometimes used as substitute for peanuts.
African cuisine used the entire fruit: Seeds are eaten as snacks, added to dishes, ground in flour; rind can be stir-fried, stewed, candied, pickled, or grilled; flesh eaten or juiced or fermented into alcohol. (26)
- The juice of
the roots used for hemorrhage after abortion.
- Juice of fruit use as antiseptic in typhus fever.
- With cumin and sugar, juice is used as a cooling drink in strangury and affections of the urinary organs, such as gonorrhea; also used for hepatic congestion and intestinal catarrh.
- In China, rind of the fruit is powdered after drying and incineration and
used for aphthous mouth sores.
- Pulp is used as a drastic purgative.
- In Tonkin, pericarp used for diarrhea.
- Seeds used to alleviate symptoms of acute cystitis.
- In traditional Chinese medicine, used to relieve scanty urination, excessive thirst, for treating icteric hepatitis and urinary tract infections.
- Used in Chinese herbal medicine for erectile dysfunction, acne, diabetes, nephritic edema.
- Water source / Alternative Food Source: In the semi-arid central Tanzania, water melons are available in appreciable quantities to be used as livestock as water source during the dry season. One hectare can produce sufficient water melons to supply water to a growing bull for 3-5 months. In years of famine, the rind is dried and made into porridge. Farmers also extract oil from the melon seeds to use for cooking.
• Hypothyroidism: Protective
role of Mangifera indica, Cucumis melo and Citrullus vulgaris peel extracts
in chemically induced hypothyroidism: Results showed thyroid
stimulatory and antiperoxidase roles. (1)
/ Repellent: Mosquitocidal and repellent activity of the leaf
extract of Citrullus vulgaris (cucurbitaceae) against the malarial vector,
Anopheles stephensi liston (diptera culicidae): The C vulgaris
plant showed insect growth regulatory activity against Anopheles stephensi.
• Thyroid Stimulation
/ Regulation of Lipid Peroxidation: Study of the fruit peel extracts of M indica, C melo and Citrullus vulgaris showed stimulatory thyroid activity in PTU-induced hypothyroid animals and lipid peroxidation inhibition. but only when treated individually. A parallel increase in hepatic and renal LPO was observed when used in combination.
• Citrulline / Rind: Watermelon is a natural and rich source of the non-essential amino acid citrulline. It is used in the nitric oxide system, with potential antioxidant and vasodilatory effects. Red flesh watermelons had slightly less citruline than yellow or orange flesh watermelons. Rind contains more citrulline than flesh. The watermelon rind, an underutilized agricultural waste, presents as a rich source of natural citrulline. (5)
• Supplementation / Improved Aortic Blood Pressure: Study showed watermelon supplementation improves aortic hemodynamics through a decrease in the amplitude of the reflected wave in individuals with prehypertension. Supplementation was well tolerated by all subjects, with no adverse effects reported.
• Antioxidant: Of eleven fruits studied, C. vulgaris was next to Phyllanthus emblica in total antioxidant capacity.
• Antimicrobial: Study showed the leaves extract of C. colocynthis, C. lanatus and C. vulgaris were very effective against bacteria and some fungal strains than other species. All three showed maximum inhibition against E. coli and Candida albicans.
• Anti-Diabetic Effect: Study evaluated the anti-diabetic potential of various extracts of watermelon in vivo in streptozotocin induced diabetic mice. Results showed significant reduction of blood glucose levels, increased insulin levels, and protection from pancreatic cell death. Results showed beneficial antidiabetic effects. (16) A methanol seed extract showed significant reduction of plasma glucose at weeks 2 and 4 in a study on female Wistar rats. Possibly, the hypoglycemia was induced by triggering of insulin release from the pancreatic ß-cells or by hepatic glucose reduction. (21)
• Corrosion Inhibitor / Peels: Study showed Citrillus vulgaris peels can serve as effective inhibitor on zinc in natural sea water environment. Results suggest the adsorption of inhibitor on zinc metal surface is exothermic and followed by spontaneous process. (17)
• Anti-Obesity / Anti-Arthritic / Seeds: Study evaluated the anti=obesity and anti-arthritic activities of seed extracts of C. vulgaris in rat models. The extracts exhibited significant anti-obesity activity with reduction of glucose, cholesterol, LDL, VLDL, triglycerides, with increase in HDL in induced obesity models in rats, with Sibutramine as standard reference. Extracts also showed significant anti-arthritic activity in FA induced arthritis in rat models. (18)
• Effect on Spermatogenesis / Seeds: Study evaluated the effect of Citrillus vulgaris on spermatogenesis in Wistar rats. Results showed a significant increase in sperm population, motility and viability. (20)
• Prostatic Hyperplasia / Seeds: Study evaluated the effects of a methanolic extract of Citrullus lanatus seed on experimentally induced benign prostatic hyperplasia in adult male Wistar rats. Treatment with the extract caused a significant decrease in prostate enlargement, seminal vesicle and testes size, together with a decrease in prostate weight. (24)
• Increased Testosterone / Seeds: Study in adult Wistar albino rats showed a significant increase in serum testosterone at 30 mg/kg of extract (P <0.05). (27)
• Radioprotective Effect / Lymphocyte Membrane: Study investigated the mechanisms of radioprotection on lymphocyte membrane in adult male Sprague-Dawley rats. Results showed Citrullus vulgaris has radioprotection properties and lymphocytes were destroyed by formation of pores on their membrane. Radioprotection could be due to the presence of antioxidants, particularly vitamin A, C, and lycopene. (28)
• Analgesic / Peels: Study of aqueous extract of C. lanatus peels for analgesic activity using Eddy's hot plate method showed good analgesic potential with a potential as alternative to conventional NSAIDS. (29)
In the news
/ Natural Viagra®: The fruit is rich in the amino acid citrulline, which is converted to the amino acid arginine (L-arginine is the precursor for endothelial nitric oxide synthesis), which is known to relax and dilate blood vessels, an effect similar to Viagra and other drugs used to treat erectile dysfunction. A 4-ounce serving of watermelon (about 10 watermelon balls) provides about 150 milligrams of citrulline. A 2007 study of volunteers who drank three 8-ounce glasses of watermelon juice daily for three weeks boosted their arginine levels by 11%. However, like many herbs and fruits touted as herbal viagra, the citrulline-viagra connect is short on science. Men with erectile dysfunction are not deficient in arginine. Still, alternative practitioners recommend citrulline for the treatment of impotence. The normal supplemental dose is 16 to 18 g of citrulline malate.
Watermelon-induced citrullinemia and urea
cycle disorders: Elevated plasma citrulline and arginine due
to consumption of Citrullus vulgaris (watermelon): A Case of
a 19-month old with developmental delay who developed watermelon-induced
citrullinemia. Its laboratory hallmarks are elevation of plasma citrulline
and moderate elevation of plasma arginine.
• While high levels of citrulline might not affect most people, it can be harmful to those with citrullinemia, a genetic disorder affecting the urea cycle.
• Current dietary management
of citrullinemia and other urea cycle disorders include restriction
of protein, sodium benzoate, and certain dietary supplements or essential
amino acids with intermediates such as arginine. One fruit
that should be avoided is watermelon (Citrullus
- Citrulline supplements.