Custard apples are also known as "sugar apples" or "sweetsop" due to the sweet taste of the fruit flesh (taste like "custard"). It is commonly known as "sitaphal" in India. The scientific name of custard apple is Annona squamosa or Annona asiatica.
A custard apple is circular, oval, or oblong-shaped. It is green in colour, and segmented. Upon ripening of the fruit, the segments separate, and the flesh is exposed.
The flesh is creamy white to white in colour, and extremely sweet to taste. Each fruit has around 30 to 35 seeds, which are brown or black in colour. A layer of the sweet-tasting flesh covers each seed separately. Sometimes, the flesh can be present without the seed being covered by it.
The flesh-covered seeds are themselves present in the form of individual segments around the core, which is conical in shape. The average weight of each fruit is around 150-200 grams.
Some of the nutritional benefits of custard apples are as follows -
• Despite its sweet taste, custard apple has a low glycaemic index of 54 (glycaemic index is defined as the rate at which glucose is released into the bloodstream by the pancreas). Since glycaemic index of custard apple is low, glucose is released gradually into the bloodstream. There is a steady, continuous supply of energy in order to perform physical activity.
• Custard apple is a powerhouse of Vitamin C (36.3 mg of Vitamin C for 100 grams of serving size of fruit). Vitamin C, also known as ascorbic acid, is required for developing immunity against illnesses such as common cold, faster healing of wounds, preventing gum bleeding, etc. As Vitamin C is water-soluble, any excessive consumption is balanced out due to excretion in the form of perspiration and urination.
• Custard apples are a good source of soluble dietary fibre (4.4 grams of soluble dietary fibre per 100 grams of serving size of fruit). Soluble dietary fibre is responsible for the feeling of "fullness" after consuming a meal. This reduces hunger, and therefore, prevents unnecessary consumption of calories. Soluble dietary fibre also lowers LDL ("bad" cholesterol) levels by reducing the reabsorption of bile by the intestines.
• Custard apples are good sources of potassium (247 mg of potassium per 100 grams of serving size of fruit) 4. As the body cannot store potassium, this nutrient needs to be consumed from the diet. Potassium is required for proper muscular contraction - muscular cramps occur due to dehydration and loss of potassium from the body. Potassium also maintains osmotic balance in the body, and helps regulate blood pressure.
• Custard apples are good sources of Thiamine or Vitamin B1 (0.110 mg per 100 grams of serving size of fruit). Thiamine is not synthesized by animals. Therefore, it has to be obtained from the diet. The active form of thiamine, Thiamine pyrophosphate (TPP), is involved in the conversion of pyruvate to Acetyl CoA during the metabolism of carbohydrates. Certain enzymes require the presence of thiamine in order to synthesize neurotransmitters. Thiamine is also required for hydrochloric acid (HCl) production in the stomach.
• Custard apple is a rich source of niacin (0.883 mg of niacin per 100 grams of serving size of fruit). Niacin reduces LDL ("bad" cholesterol) levels and increases HDL ("good" cholesterol) levels. 8 Niacin also reduces hardening of arteries, known as atherosclerosis. Niacin also increases dilation of blood vessels, improving blood flow.
Besides the custard apple fruit, research has shown that the entire Annona squamosa plant itself possesses numerous health benefits. Some of them are described as follows -
• Anti-HIV activity - A compound called 16 Beta,17-dihydroxy-ent-kauran-19-oic acid has been isolated from Annona squamosa. Research shows that this compound acts significantly against replication of HIV in H9 human lymphocyte cell lines. Therefore, it may be concluded that certain compounds present in custard apples show "anti-HIV replication" activity.
• Anti-oxidant activity - Extracts obtained from the peel and seeds of custard apples have been shown to possess antioxidant activity.
Diabetes is associated with oxidative stress. The aqueous extract of the leaves of custard apple has been shown to possess antioxidant activity in diabetic animal models as indicated by the increased levels of enzymes such as catalase, superoxide dismutase, glutathione reductase, etc. This aqueous extract of custard apple leaves can also help in the management of high cholesterol and triglyceride levels which are associated with type 2 diabetes.
• Anti-diabetic activity - Laboratory research has shown that the aqueous extract of the leaves of custard apples displays a hypoglycaemic and anti-diabetic effect in animal models.
The pulp of the custard apple fruit has been shown to reduce blood glucose levels in diabetic rats. It has also been shown that custard apple fruit pulp helps protect the liver and heart in such organisms, as well as reduce the levels of critical parameters such as SGPT, SGOT, serum bilirubin, and ALKP.
• Anti-tumour activity - The bark of Annona squamosa has been shown to possess anti-tumour activity.
Aqueous and ethanolic extracts of bark of A. squamosa have been studied for their antigenotoxic effects on hamsters injected with 7,12 dimethylbenz(a)anthracene (DMBA), an organ-specific carcinogen. Although both extracts displayed antigenotoxic effects, it was found that the ethanolic extract of the bark possesses greater antigenotoxic effect as compared to the aqueous extract.
A. squamosa seeds have been used in Chinese medicine as anti-malignant therapy as well as an insecticide. Research has shown that six annonaceous acetogenins have been isolated from A. squamosa seeds which possess cytotoxic properties and show anti-tumour activity.
• Wound-healing properties - Annona squamosa leaves have been shown to possess wound-healing properties in diabetic rats. In one group of diabetic rats, wounds were treated with aqueous extract of custard apple leaves, whereas the wounds were left untreated in the control group. The rates of wound contraction and epithelial tissue formation increased in the treated test group, as compared to untreated control group, where no wound healing took place. Therefore, it may be concluded that topical application of ethanolic extract of custard apple leaves enhances rate of wound healing in diabetic organisms.
• Anti-pathogenic action - Methanol extracts of A. squamosa seeds contain annonaceous acetogenins which display nematicidal and antifungal properties against plant pathogens. Therefore, these compounds have great potential to be used as biological nematicides and fungicides for agricultural purposes.
Methanolic leaf extract of A. squamosa has potential mosquitocidal activity as shown against the filarial mosquito Culex quinquefasciatus.
• Other health benefits - The leaf extract of Annona squamosa could be potentially used as preventive therapy against foodborne illnesses.
Seed extracts of A. squamosa (along with possible involvement of quercetin) have been shown to regulate hyperthyroidism in mice.
Peel extract of A. squamosa can be used for the synthesis of silver and palladium nanoparticles, both of which are highly useful in medical nanoscience.
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7. Thiamine (Vitamin B1) http://www.mayoclinic.com/health/vitamin-b1/NS_patient-thiamin
8. Niacin http://www.healthcentral.com/encyclopedia/408/322.html?ic=506048
9. Niacin (Vitamin B3) http://www.webmd.com/vitamins-and-supplements/lifestyle-guide-11/supplement-guide-niacin
10. Supplements That Dilate Blood Vessels http://www.livestrong.com/article/292758-supplements-that-dilate-blood-vessels/
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21. Dang QL, Kim WK, Nguyen CM, et al - Nematicidal and antifungal activities of annonaceous acetogenins from Annona squamosa against various plant pathogens - J Agric Food Chem. 2011 Oct 26;59(20):11160-7 http://www.ncbi.nlm.nih.gov/pubmed/21910504
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29. Image source: http://en.wikipedia.org/wiki/Annona_senegalensis
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