Abstract
Soursop fruit has been used in folklore for the management of type-2 diabetes and hypertension with limited information on the scientific backing. This study investigated the effects of aqueous extracts (1 : 100 w/v) of Soursop fruit part (pericarp, pulp, and seed) on key enzymes linked to type-2 diabetes (α-amylase and α-glucosidase) and hypertension [angiotensin-I converting enzyme (ACE)]. Radicals scavenging and Fe2+ chelation abilities and reducing property as well as phenolic contents of the extracts were also determined. Our data revealed that the extracts inhibited α-amylase and α-glucosidase and ACE activities dose-dependently. The effective concentration of the extract causing 50% antioxidant activity (EC50) revealed that pericarp extract had the highest α-amylase (0.46 mg/mL), α-glucosidase (0.37 mg/mL), and ACE (0.03 mg/mL) inhibitory activities while the seed extract had the least [α-amylase (0.76 mg/mL); α-glucosidase (0.73 mg/mL); and ACE (0.20 mg/mL)]. Furthermore, the extracts scavenged radicals, reduced Fe3+ to Fe2+, and chelated Fe2+. The phenolic contents in the extracts ranged from 85.65 to 560.21 mg/100 g. The enzymes inhibitory and antioxidants potentials of the extracts could be attributed to their phenolic distributions which could be among the scientific basis for their use in the management of diabetes and hypertension. However, the pericarp appeared to be most promising.
Discussion
The observed inhibitory effect of the Soursop fruit part extracts on α-amylase and α-glucosidase activities in vitro suggests the possible mechanism by which Soursop fruit parts exert their antidiabetic effect and may be part of the underlying basis for their folkloric use in the management/treatment of diabetes. Several studies have revealed that α-amylase and α-glucosidase activity have a great influence on blood glucose level and their inhibition could significantly reduce the postprandial increase of blood glucose . It has also been established that reducing postprandial hyperglycemia is an important strategy towards type-2 management . From this study, the pericarp of the fruit which had the highest total phenol and flavonoid content exhibited the highest α-amylase and α-glucosidase inhibitory effects. This is consistent with earlier studies where α-amylase and α-glucosidase inhibitory effect of plant foods are attributed to their phenolic constituents. In addition, the fact that Soursop extracts significantly (P < 0.05) inhibited α-glucosidase more than α-amylase is of therapeutic importance at preventing the unpleasant side effects associated with strong synthetic α-amylase inhibitors, such as acarbose, and also agrees with previous studies that plant phenolic-rich extract inhibited α-glucosidase activity better than α-amylase activity.
Although inhibitors of ACE activity are antihypertensive agents, they have been reported to reduce the risk of developing of type-2 diabetes. ACE inhibitors stimulate the release of bradykinin which, in turn, enhances the responsiveness of both muscle fiber and adipocytes to insulin utilization. From the result, a strong correlation between the ACE inhibitory effects of the Soursop fruit extracts and the phenolic content was observed. The ability of the plant bioactive compounds such as phenolics could inhibit ACE activity. It is proposed that phenolic phytochemicals showed a structure-function relationship in inhibiting ACE activity by chelating the active site zinc ion or inducing the formation of hydrogen bridges between the active site amino acid residues and the phenols. This study showed strong correlation between the ACE inhibitory effect and the phenolic contents, as evidenced by the efficacy of the fruit pericarp with the highest phenolic contents. In line with increased interest in natural products as alternative to synthetic drugs, it is believed that these extracts would have little or no side effects when compared to these synthetic ACE inhibitor drugs such as captopril.
One of the risk factors in type-2 diabetes mellitus and its cardiovascular complication (hypertension) is oxidative stress. Oxidative stress has been reported to play a vital role in the etiology and development of type-2 diabetes and hypertension. Free radicals induced oxidative damage of pancreatic β-cells has been implicated in impaired insulin production/function, a major risk factor of diabetes development. Also, oxidative damage to endothelia cell of the blood vessel could compromise the elasticity of the vessel resulting in hypertension or some other cardiovascular complications. Thus combating oxidative stress could be a practical way to ensure holistic management of type-2 diabetes and hypertension. Therefore, it is imperative to investigate the antioxidant properties of Soursop fruit extracts, which have been reported in folklore medicine to be potent in the management of several diseases including diabetes and hypertension.
Polyphenolic compounds have shown antioxidant properties by reduction of Fe3+ to Fe2+, chelation of Fe, and mopping of radicals. ABTS radical, a protonated radical, have characteristic absorbance maxima at 734 nm which decrease with the scavenging of the proton radicals, while the DPPH radical scavenging ability is through hydrogen ion donating ability. This study showed that the extracts were able to scavenge (DPPH and ABTS) free radicals. The pericarp extract had the highest scavenging abilities as well as the highest total phenol and flavonoid contents.
Free radicals are capable of inducing oxidative damages in biomolecules via several reaction processes. One of such reactions is the Fenton reaction in which degradation of deoxyribose is initiated through Fe2+ catalyzed hydrogen peroxide (H2O2) decomposition to produce OH radicals. The antioxidant properties of the Soursop fruit part extracts can also be measured by the ability to prevent degradation of deoxyribose via scavenging of hydroxyl (OH) radical and chelation of transition metals such as Fe2+. As observed in this study, OH radical scavenging and Fe2+ chelating abilities of the Soursop fruit parts (pericarp, pulp, and seed) extracts could be explored in the management oxidative stress-induced degenerative disease such as diabetes and hypertension. The report of this study is in line with previous studies indicating the ability of the phenolic compounds to chelate and/or deactivate transition metals and prevent such metals from participating in the initiation of lipid peroxidation and oxidative stress through metal catalysed reaction. The pericarp from the fruit also exerted the highest Fe2+ chelating ability. This is further buttressed by the agreement between the antioxidant properties of the various Soursop fruit extracts and their phenolic contents.
Recently, polyphenolic compounds have become subjects of interest because of their beneficial effects on human health. Numerous studies have shown that majority of the antioxidant activity of plants food is from phenolic compounds such as flavonoids, isoflavones, flavones, anthocyanins, catechin, and isocatechin rather than from vitamins C and E and β-carotene and is believed to be due to their redox properties, which play a crucial role in adsorbing and neutralizing free radicals, quenching singlet and triplet oxygen, decomposing peroxides, chelating metal catalysts, and activating antioxidant enzymes. According to Jiménez et al., about sixteen phenolic compounds were reported to be predominantly present in Soursop fruit pulp. Cinnamic acid derivatives, p-coumaric acids together with several other minor compounds, were identified as the major phenolic compounds in Soursop fruit. However, this study suggests that these phenolics may be well distributed in all the Soursop fruit part. Thus, this study showed that the pericarp had the highest total phenol content, followed by the pulp while the seed had the least phenolic contents. This study further revealed that there are strong correlations between the phenolics contents and the biological activities studied. Therefore, phenolics in the Soursop fruit parts (pericarp, pulp, and seed) may be part of the active compound responsible for the antioxidant, antidiabetic, and antihypertensive and may provide a scientific basis of their use in folklore medicine. It is worth noting that the higher phenolic contents in the pericarp compared to the pulp and seed of the fruit could be due to the fact that the pericarp is more exposed to the environmental stress factors such as ultraviolet ray from the sunlight. Stress factors provoke intense synthesis of phenolic compounds in the plant in order to forestall oxidative damage where the stress factors could confer to the plant cellular structures [45], unlike the pulp and seed that are protected by the edible portion of the fruit and therefore have less exposure to such stress factors. However, the values obtained for the extracts are lower than what was reported in some edible plant obtained in Iran and India but higher than phenolics content in some selected tropical fruits from Malaysia. To the best of our knowledge, this is the first time that the phenolic distribution and biological effects of Soursop fruit parts (pericarp, pulp, and seed) were reported.
Conclusion
This research investigated and revealed that Soursop fruit extracts possess antioxidant properties and were able to inhibit key enzymes relevant to type-2 diabetes mellitus (α-amylase and α-glucosidase) and hypertension (angiotensin-I converting enzyme) in vitro. The antidiabetic, antihypertensive, and antioxidant properties of the fruits part were strongly correlated to the phenolic contents. The combined enzyme inhibitory and antioxidant properties could be part of the biochemical rationale behind the traditional use of the Soursop fruit in the prevention and management of diabetes and hypertension. Nevertheless, this research has shown that Soursop's pericarp had the highest enzyme inhibitory and antioxidant properties compared to other parts (pulp and seed).
Research Orginally posted at www.ncbi.nlm.nih.gov
Introduction
Of the 60 or more species of the genus Annona, family Annonaceae, the soursop, A. muricata L., is the most tropical, the largest-fruited, and the only one lending itself well to preserving and processing.
It is generally known in most Spanish-speaking countries as guanabana; in E1 Salvador, as guanaba; in Guatemala, as huanaba; in Mexico, often as zopote de viejas, or cabeza de negro; in Venezuela, as catoche or catuche; in Argentina, as anona de puntitas or anona de broquel; in Bolivia, sinini; in Brazil, araticum do grande, graviola, or jaca do Para; in the Netherlands Antilles, sorsaka or zunrzak, the latter name also used in Surinam andJava; in French-speaking areas of the West Indies, West Africa, and Southeast Asia, especially North Vietnam, it is known as corossol, grand corossol, corossol epineux, or cachiman epineux. In Malaya it may be called durian belanda, durian maki; or seri kaya belanda; in Thailand, thu-rian-khack.
In 1951, Prof. Clery Salazar, who was encouraging the development of soursop products at the College of Agriculture at Mayaguez, Puerto Rico, told me that they would like to adopt an English name more appealing than the word "soursop", and not as likely as guanabana to be mispronounced. To date, no altematives have been chosen.
Food Uses
Soursops of least acid flavor and least fibrous consistency are cut in sections and the flesh eaten with a spoon. The seeded pulp may be torn or cut into bits and added to fruit cups or salads, or chilled and served as dessert with sugar and a little milk or cream. For years, seeded soursop has been canned in Mexico and served in Mexican restaurants in New York and other northern cities.
Most widespread throughout the tropics is the making of refreshing soursop drinks (called champola in Brazil; carato in Puerto Rico). For this purpose, the seeded pulp may be pressed in a colander or sieve or squeezed in cheesecloth to extract the rich, creamy juice, which is then beaten with milk or water and sweetened. Or the seeded pulp may be blended with an equal amount of boiling water and then strained and sweetened. If an electric blender is to be used, one must first be careful to remove all the seeds, since they are somewhat toxic and none should be accidentally ground up in the juice.
In Puerto Rican processing factories, the hand-peeled and cored fruits are passed through a mechanical pulper having nylon brushes that press the pulp through a screen, separating it from the seeds and fiber. A soursop soft drink, containing 12 to 15% pulp, is canned in Puerto Rico and keeps well for a year or more. The juice is prepared as a carbonated bottled beverage in Guatemala, and a fermented, cider-like drink is sometimes made in the West Indies. The vacuum-concentrated juice is canned commercially in the Philippines. There soursop drinks are popular but the normal "milk" color is not. The people usually add pink or green food coloring to make the drinks more attractive. The strained pulp is said to be a delicacy mixed with wine or brandy and seasoned with nutmeg. Soursop juice, thickened with a little gelatin, makes an agreeable dessert.
In the Dominican Republic, a soursop custard is enjoyed and a confection is made by cooking soursop pulp in sugar sirup with cinnamon and lemon peel. Soursop ice cream is commonly frozen in refrigerator ice-cube trays in warm countries.
In the Bahamas, it is simply made by mashing the pulp in water, letting it stand, then straining to remove fibrous material and seeds. The liquid is then blended with sweetened condensed milk, poured into the trays and stirred several times while freezing. A richer product is made by the usual method of preparing an ice cream mix and adding strained soursop pulp just before freezing. Some Key West restaurants have always served soursop ice cream and now the influx of residents from the Caribbean and Latin American countries has created a strong demand for it. The canned pulp is imported from Central America and Puerto Rico and used in making ice cream and sherbet commercially. The pulp is used, too, for making tarts and jelly, sirup and nectar. The sirup has been bottled in Puerto Rico for local use and export. The nectar is canned in Colombia and frozen in Puerto Rico and is prepared fresh and sold in paper cartons in the Netherlands Antilles. The strained, frozen pulp is sold in plastic bags in Philippine supermarkets.
Immature soursops are cooked as vegetables or used in soup in Indonesia. They are roasted or fried in northeastern Brazil. I have boiled the half-grown fruit whole, without peeling. In an hour, the fruit is tender, its flesh off-white and mealy, with the aroma and flavor of roasted ears of green corn (maize).
Medicinal Uses
The juice of the ripe fruit is said to be diuretic and a remedy for haematuria and urethritis. Taken when fasting, it is believed to relieve liver ailments and leprosy. Pulverized immature fruits, which are very astringent, are decocted as a dysentery remedy. To draw out chiggers and speed healing, the flesh of an acid soursop is applied as a poultice unchanged for 3 days.
In Materia Medica of British Guiana, we are told to break soursop leaves in water, "squeeze a couple of limes therein, get a drunken man and rub his head well with the leaves and water and give him a little of the water to drink and he gets as sober as a judge in no time." This sobering or tranquilizing formula may not have been widely tested, but soursop leaves are regarded throughout the West Indies as having sedative or soporific properties. In the Netherlands Antilles, the leaves are put into one's pillowslip or strewn on the bed to promote a good night's sleep. An infusion of the leaves is commonly taken internally for the same purpose. It is taken as an analgesic and antispasmodic in Esmeraldas Province, Ecuador. In Africa, it is given to children with fever and they are also bathed lightly with it. A decoction of the young shoots or leaves is regarded in the West Indies as a remedy for gall bladder trouble, as well as coughs, catarrh, diarrhea, dysentery and indigestion; is said to "cool the blood," and to be able to stop vomiting and aid delivery in childbirth. The decoction is also employed in wet compresses on inflammations and swollen feet. The chewed leaves, mixed with saliva, are applied to incisions after surgery, causing proudflesh to disappear without leaving a scar. Mashed leaves are used as a poultice to alleviate eczema and other skin afflictions and rheumatism, and the sap of young leaves is put on skin eruptions.
The roots of the tree are employed as a vermifuge and the root bark as an antidote for poisoning. A tincture of the powdered seeds and bay rum is a strong emetic. Soursop flowers are believed to alleviate catarrh.
Full article posted at hort.purdue.edu
Also called graviola, soursop is a large, spiny, green tropical fruit with a sweet flesh that is the basis for several beverages, ice creams and other sweet foods popular in South America. Beyond its usefulness as a food, however, soursop also contains natural compounds with medicinal properties, making it potentially beneficial for your health.
Soursop
The graviola tree, or Annona muricata, produces the sweet soursop fruit, also called custard apple, paw paw or, in many Spanish-speaking countries, guanabana. The tree reaches a height of 25 or 30 feet and produces large fruit that may reach a length of 12 inches. Although its rind is quite bitter, the fruit's flesh is soft, smooth and sweet, and provides carbohydrate as its major nutrient. Soursop also contains abundant vitamin C and several B vitamins such as thiamin, riboflavin and niacin, along with calcium, phosphorus and a small amount of iron.
Uses and Components
Practitioners of herbal medicine recommend the fruit and leaves of the graviola tree to relieve stomach distress, fever, pain and respiratory problems such as cough and asthma, and for many other medical problems. Soursop contains a number of natural substances that have biological activity, according to Memorial Sloan-Kettering Cancer Center. These include fatty compounds called acetogenins, especially one called annonacin, along with other compounds called quinolones, annopentocins and two alkaloids, coreximine and reticuline. Soursop's acetogenins are the compounds that have been most studied, especially for their potential to prevent or slow the growth of cancer. The Cancer Center also says that some compounds in soursop may be naturally antiviral and antiparasitic, and may also suppress inflammation.
Research
Laboratory research supports the potential benefits of soursop as a remedy for disease. In one study, published in "Journal of Ethnopharmacology," an extract of soursop inhibited the growth of Herpes virus in the laboratory. In addition, the Cancer Center summarizes findings that suggest soursop extracts might slow growth of cancer cells or make them more susceptible to anti-cancer drugs. For example, in one study published in 1997 in "Journal of Medicinal Chemistry," compounds from soursop were tested on breast cancer cells in culture and found to be up to 250 times more effective in killing the cells than some chemotherapy drugs. These laboratory studies with soursop are promising, but research with human subjects is needed to confirm its potential usefulness.
Recommendations
The recommended intake of soursop fruit or its extract has not been established. However, one fruit contains about 15 milligrams of annonacin, its most studied component, and one can of commercially prepared soursop nectar provides 36 milligrams. Avoid consuming soursop in excess, however, since large quantities of its alkaloid compounds may cause neurological symptoms similar to Parkinson's disease. Do not self-treat with soursop or its extract. Discuss its use with your doctor to decide what is best for your situation.
Article Orginally posted at healthyeating.sfgate.com