Exotic Fruits from India

Recently there has been growing consumer interest in “exotic” (terminology currently used to refer to “mysteriously different” or “unusual”) fruits due to anecdotal claims of their medicinal values and purported health benefits. This has been fueled, in part, by a shift in ethnic demographics as immigrants bring native foods common to their cultures to the Western marketplace. Popular examples of such fruits include the pomegranate ( Punica granatum ), açaí, goji berries, mangosteen, and noni.

Although exotic fruits are found in all parts of the world, India, which is blessed by a rich diversity of climatic zones-from tropical to tundra-is home to several exotic fruits that have attracted recent consumer attention. A perennial leader in the production of amla ( Emblica officinalis syn. Phylanthus emblica , also known as Indian gooseberry), mango, papaya, and tamarind, India also produces what many regard as the sweetest pomegranates available.

Because of India's strong agricultural foundation and its thousands of years of traditional medicinal use of fruits, as well as the recent focus of modern research into the bioactive properties of the fruits, we are now graced with a growing wealth of knowledge on the potential uses for what we may call the Indian superfruits: pomegranate, mango, papaya, amla, and tamarind.

These fruits include the pomegranate, amla, and jamun berries ( Eugenia jambolana syn. Syzygium cumini ). In terms of their phytochemistry, these fruits share a commonality in that they all contain ellagitannins (ETs), a family of polyphenols that have been linked with a diverse range of biological activities.

ETs are obtained in the Western diet primarily through the consumption of berries and tree nuts such as strawberries, red and black raspberries, walnuts, and almonds. Emerging science has demonstrated that ET-rich foods may impart human health benefits, including antineurodegenerative, antidiabetic, and anticancer properties.

Although many drug-discovery research groups seek to identify single active ingredients in medicinal foods, there has been a shift in this paradigm in the functional foods and dietary supplement arenas. This is because multiple phytochemicals present in a complex food matrix may provide better protection through complementary, additive, or synergistic effects. Therefore the consumption of bioactive food components in whole foods and their derived extracts offers an attractive dietary strategy for the prevention or delay of onset of several chronic human diseases. Due to the paucity of clinical data, however, there is great need for well-designed human clinical studies to substantiate the health claims of many of these fruits.

Pomegranate

Pomegranate juice, peels, and seeds are an ancient mainstay of Ayurveda, the traditional Indian system of medicine. Pomegranate deserves special mention among the aforementioned fruits, because it has the most published clinical data to support its health benefits, specifically against cardiovascular disease and prostate cancer.^1–4 The fruit peel is a rich source of hydrolyzable ETs, including punicalagins, punicalins, gallagic acid, several ellagic acid-glucose esters, and oligomeric ETs. Pomegranate juice obtained from squeezing the whole fruit provides more potent antioxidants than other common fruit juices.^5,6

Since 2006, the antioxidants in pomegranate fruit extracts and juices have been studied in vivo or clinically for applications in cardiovascular, glycemic, cellular/DNA, and cognitive health, in addition to gender-related health issues. The triple-whammy of antioxidant, antiinflammatory, and antimicrobial effects also has led to research in skin- and oral-care applications.

Bioavailability, metabolism, and ex vivo bioactivities of pomegranate ETs have been established for both juice and extract preparations.^7–10 On consumption, pomegranate ETs release ellagic acid (EA). Following metabolism by gut flora, the ETs form urolithins that are conjugated in the liver prior to excretion up to 56 hours in urine. These urolithins circulate in the blood as well and can reach many of the target organs, such as the prostate gland, where the effects of pomegranate ETs have been noted.¹¹

Pomegranate juice also contains other polyphenols included among its minor constituents, such as anthocyanins, the pigments that impart the red color to the fruit aril and therefore to fruit juice. Pomegranate extracts have been shown to inhibit prostate cancer xenografts in animal studies^11,12 and to date there is a phase-II human clinical that suggests effects against prostate cancer.⁴ It is noteworthy that ETs previously were shown to exhibit in vitro and in vivo anticarcinogenic properties, such as induction of cell-cycle arrest and apoptosis in vitro.¹³ A recent review on the effects of pomegranate ETs on cancer is available.²

The absorption of a pomegranate extract standardized to punicalagins, Pomella Extract (supplied by Verdure Sciences Inc.; Noblesville, IN), was analyzed by measuring a time-curve of EA in human plasma. In this study, a 32% increase in antioxidant capacity was observed as a result of consumption of the extract.²³

Amla

The amla fruit, touted as one of nature's richest sources of vitamin C, is also known to contain ETs and other polyphenols, including emblicanins A and B.4 Amla fruits constitute one of three ingredients in a well-known antioxidant-rich Ayurvedic herbal formulation, Triphala (the other two Indian fruits are Terminalia chebula and T. belerica ).

Amla is used for the treatment of liver diseases, stomach ulcers, inflammatory diseases, and also to inhibit tumor growth, in diabetes and in geriatric complaints.¹⁴ Recently, a preparation of amla fruit was shown to prevent liver toxicity¹⁵ and age-related renal dysfunction.¹⁶

Jamun

Obtained from a large evergreen tree that reaches up to 30 meters in height, Jamun fruits have been valued in both Ayurvedic and Unani systems of medicine for possessing a wide variety of therapeutic properties.^17,18 Jamun is most often recognized as an adjuvant therapy in type-2 diabetes. This has been traced not only to its anthocyanin-rich, dark-purple fleshy pulp, but also to its seeds, which have been most studied for their antidiabetic principles.18 Jamun seeds are reported to be a rich source of ETs, including corilagin, 3,6-hexahydroxydiphenoylglucose and its isomer 4,6- hexahydroxydiphenoylglucose, 1-galloylglucose, 3-galloylglucose, gallic acid, and EA.¹⁷

Jamun fruit seeds and pulp have been reported to serve various purposes in diabetic patients, such as lowering blood glucose levels and delaying diabetic complications including neuropathy and cataracts. However, most of the studies have been conducted using a crude preparation of E. jambolana fruit parts without mention of their chemical profile. Therefore, detailed research that identifies the antidiabetic bioactive components, using well-characterized and standardized fruit pulp and/or seed extracts, is urgently needed.

Mango

Although mango fruit ( Mangifera indica ) is widely consumed as a whole ripe fruit in diets of tropical populations worldwide, it also is widely consumed in Indian cuisine in mango chutneys, which include preparations of the bitter and unripe mango flesh, seeds, and peel. Mango is a good source of carotenoids, ascorbic acid, quercetin, xanthone, mangiferin, and other polyphenols. Recently, a mango peel extract prevented degradation of rat erythrocytes,¹⁹ a mango extract prevented mitochondrial oxidative stress in an atherosclerotic mouse model²⁰, and the mango triterpene lupeol also has been shown to inhibit certain cancers in in vivo models.²¹

Garcinia

Garcinia cambogia is a small fruit indigenous to India, where it is often used in Indian cuisine for the purposes of adding a “sour-tasting ingredient” to curries. An extract from G. camobgia fruit and its rind is popularly used with claims of “weight-loss” effects.

G. cambogia fruit and its extract contain large quantities of hydroxycitric acid (HCA), which is believed to be the putative active component and is claimed to suppress appetite and enhance fat-burning.²² Recent reports have shown that apart from HCA, the fruit also contains polyisoprenylated benzophenones and xanthones.²³ Given the paucity of data available on the weight-loss potential of this fruit, more detailed clinical studies are needed.

India ranks second only to China in production of fruit, with 46 million tons produced per year.1 With this abundant wealth of supply and forthcoming research, India's superfruits are sure to continue to endow the world with an ever-impressive array of fruit-derived ingredients.

Navindra P. Seeram, PhD, is currently an assistant professor of pharmacognosy at the University of Rhode Island's College of Pharmacy (Kingston, RI). His research interests include the evaluation of medicinal plants and bioactive food components for the prevention and therapy of chronic human illnesses including cancer, diabetes, and neurodegenerative diseases.

REFERENCES

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