Exotic Antioxidant Superfruits

Exploring Exotic Antioxidant Superfruits
In a global quest for novel sources of nutrients, health-promoting phytochemicals, and exotic tastes or colorants, the functional food industry is searching for exceptional plants in geographical niches like the Asian or South American tropics and mainland China.

Among exotic species in development for new food or beverage products and nutritional additives are three berries—açaí, sea buckthorn and wolfberry—and three tree fruits—noni, mangosteen and pomegranate.

As potential functional dietary agents, these fruits have at least four characteristics in common: 1) each is being developed primarily as a juice product; 2) each is already recognized as a significant source of antioxidant phytochemicals; 3) in ongoing laboratory research, each is revealing evidence for anti-disease properties; 4) no uses or products from any have conclusively demonstrated efficacy against human disease. Consequently, none has received scientific validation or regulatory approval for health claim statements.

Noni juice did receive approval status in late 2005 as a “novel food” in Europe. By contrast, the same year, France issued warnings that consumption of 30 ml/day of noni juice could increase the risk of contracting hepatitis,1 a finding now disputed.2

This brief review will summarize available nutritional information for these fruits, including a look at peer-reviewed research, and provide a numerical measure of antioxidant strength—the oxygen radical absorbance capacity, ORAC. Data for ORAC are presented as micromoles (µmol) of Trolox equivalents (TE) per 100 grams.

Acaí

A palm tree native to tropical Central and South America, açaí (Euterpe oleracea Mart.) is a relatively new fruit (commercial since 2000) to the current global market for functional foods. Long used among Brazilian Amazon peasants as a staple mixed with tapioca or sugar, açaí gained popularity in the United States first as a juice “energy” drink and additive to smoothies. Now, its pulp powder is being applied in a variety of other consumer products and has great potential for expansion into numerous food and beverage products. Growing in panicles of several hundred individual fruits per tree, the açaí berry is dark blue and similar in size to a grape containing a large seed.

There is only limited nutrient information available. Freeze-dried pulp powder contains 9-percent protein, 33-percent carbohydrates, 12-percent dietary fiber, and 50-percent fats comprised of 38-percent mono- and polyunsaturated fats. Its antioxidant compounds include anthocyanins (cyanidin-3-glucoside, cyanidin-3-rutinoside), procyanidins, protocatechuic acid, epicatechin, gallic acid and vitamin C. At an ORAC of 34,000 µmol TE per 100 g in freeze-dried pulp powder, it appears to be among the most antioxidant-rich edible plants.

Clinical studies are scarce, primarily limited to chemical isolation of phenolic antioxidants. There was a report with evidence the berry can inhibit leukemia cell development in vitro.3 Its potential health benefits have been unexamined at present; however, demonstration of rich phenolic content indicates potential benefits for all diseases that are purportedly also affected by blueberries and black raspberries, such as cancer, cardiovascular diseases, chronic inflammation, cognitive disorders, aging and age-related visual decline and bacterial infections, among others.

Açaí’s delicious taste, sometimes described as the marriage of blueberries with chocolate, combined with what appears to be exceptional nutrient density and antioxidant strength, assures that açaí will remain a focus of research and product development for years to come.


Research in the past few years has begun to identify characteristics which yield one of the most complex and highest nutrient densities known. There are some reports that it may contain up to 190 bioactive phytochemicals including vitamins, minerals, amino acids, fiber and more. Sea buckthorn berries are rich in lipidsoluble carotenoids and water-soluble phenolics, including high vitamin C content, and there is a high content of unsaturated fats within both the berry pulp and its seed. The juice from pressing this berry separates into three phases: a fat-rich top layer, a turbid opalescent middle, and a bottom sediment of solids.

Preliminary clinical trial results show sea buckthorn may improve blood cholesterol levels and increase resistance to oxidative stress.4 Sea buckthorn impresses as a multi-nutrient berry particularly rich in antioxidant phytochemicals and vitamins C and E. The unusual berry pulp and seed content of multiple fatty acids further indicates a plant unexploited in the West for nutrient richness and manufacturing potential. Its avid pigmentation yields high astringency and strong potential for an industrial colorant, “sea buckthorn yellow.”

Wolfberry

As a member of the plant family Solanaceae, wolfberries are related to the tomato, potato and eggplant. At maturity, the fruit is a bright red, ellipsoid berry between 1 and 2 cm in length, grows on vines, and has high juice and sugar content (brix 26). Although dozens of Lycium species exist around the world, about 90 percent of the available wolfberry commercial resource is Lycium barbarum L. from the north-central regions of China, primarily the Ningxia Hui Autonomous Region.The berries are often called “goji”, an apparent English contraction of the Mandarin name. One of the oldest medicinal plants known, wolfberries have been a staple in the diets of Chinese peasants throughout recorded time (at least 2,000 years).

Sea Buckthorn

An ancient Asian herbal remedy for many disorders in traditional Asian medicine, sea buckthorn (Hippophae rhamnoides L.) has only recently attracted attention of Western scientists. This yellow-orange berry grows on large vines dense with sharp, long thorns, making it a desirable protective hedgerow but very challenging to harvest. Sea buckthorn also has very aggressive and deep roots, making the bush valuable in China for wildlife habitat, farmstead shelter belts, land reclamation and riverbank erosion control.


Acclaimed by some as one of the world’s most nutrientrich plant foods, wolfberries contain 22 trace and 11 essential minerals, at least six essential vitamins, 18 amino acids, five unsaturated fats and at least one phytosterol, five carotenoids (including lycopene, rare among berries), six mono- and eight polysaccharides identified to date (a topic of considerable current research), and numerous additional phytochemicals. Its levels of zeaxanthin, betacarotene, riboflavin (vitamin B2), selenium and iron are among the richest concentrations per gram in the plant kingdom. One non-peerreviewed report on ORAC has wolfberry as one of the strongest antioxidant edible plants yet analyzed (30,300 µmol TE per 100 g).

While clinical trials are limited to those interpreted from Chinese abstracts with insufficient details of trial design and peer-review, there are numerous animal studies and in vitro work on phytochemical analysis. Considerable Chinese literature has been constructed around wolfberry’s potential health benefits through its diversity of phytochemicals and known nutrients.

Noni

Native to Southeast Asia but cultivated throughout the tropics, noni (Morinda citrifolia L.) is a green-to-white fruit that, when near ripening, has a foul odor and pungent taste sometimes earning its alternate names cheese fruit or even vomit fruit. Nevertheless, noni has been used for hundreds of years in Polynesia as a medicinal plant with a variety of supposed healing benefits and dietary applications.

Several references in the literature describe essential macronutrients (carbohydrates, dietary fiber), micronutrients including vitamins C and E, numerous minerals (particularly high in potassium), amino acids, omega-3 and -6 fatty acids and a number of phytochemicals including polysaccharides and carotenoids.

Its research status at this point has been relatively limited to in vitro laboratory analyses of antioxidant phytochemicals and polysaccharides. However, there is increasing focus on its potential anti-cancer mechanisms, including anti-angiogenic and apoptotic mechanisms.5

Mangosteen

The mangosteen (Garcinia mangostana L.) is a tropical evergreen tree bearing dark purple fruit with a delicious white interior giving it the name “Queen of Fruits,” possibly named after Queen Victoria’s famous desire to have the exotic fruit imported as a personal staple. It is grown mainly in the Asian, African and Pacific tropics, but is not related to the mango fruit. The two primary mangosteen components—pericarp and flesh—have different purposes in the functional food industry. The purple pericarp, not considered edible, is a rich source for extracting antioxidant phytochemicals, whereas the interior flesh is valued as a juice or pulp product.

A report from Nutritiondata.com shows the interior pulp is rich in carbohydrates and moderate in dietary fiber, fat and protein, with measured contents of beta-carotene, beta-cryptoxanthin, vitamin C, trace B vitamins, folic acid, calcium, magnesium, phosphorus, sodium, zinc and potassium. Research has primarily focused on the pericarp for its mechanisms of antioxidant xanthones on cancer models and appetite suppression. Garcinol appears to be a potent inhibitor of the cyclooxygenase-2 enzyme (COX-2) involved in inflammation and nitric oxide synthase, the enzyme responsible for nitric oxide production.6

Pomegranate

A deciduous fruit-bearing tree native to the Mediterranean Middle East, but now cultivated in many subtropical regions of the world, the pomegranate (Punica granatum L.) has been favored for centuries as a healthgiving plant, especially its brilliant red seed pulp. Juice pressed from the many seeds of each fruit has become popular for its delicious taste and rich content of antioxidant phenolics shown in an increasing number of medical studies to have powerful anti-disease potential.

Pomegranate seed pulp is primarily carbohydrate, with small amounts of fat and protein and low levels of dietary fiber. Nutrients include vitamins A (from alpha- and beta-carotene), C, E and K, folic acid, niacin (B3) and pantothenic acid, with high levels of potassium and phosphorus. Specialty antioxidant phytochemicals include punicalagin (ellagitannin), ellagic acid, gallocatechins, prodelphinidins, delphinidin, cyanidin and pelargonidin. ORAC measurements of the juice have been reported at 10,500 µmol TE/100 g.

A time-honored fruit over centuries now identified with a rich complement of antioxidant phenolics, pomegranate juice has a diversity of potential health benefits under active study. In particular, there has been a great deal of research interest in the potential role of pomegranate extracts or whole juice specifically on preventing cancer, especially prostate cancer.7 It also appears to help improve cardiovascular function, with application in blood pressure management and cholesterol.