Distribution and Importance of the Plant
The genus Vaccinium, from the heath family (Ericaceae), includes a wide range of popular berry species of economic importance, including the American cranberry (Vaccinium macrocarpon Ait.), the wild lowbush blueberry (Vaccinium angustifolium Ait.), cultivated highbush and rabbiteye blueberries (V. corymbosum L. and V. ashei Reade), bilberry (V. myrtillus L.) and lingonberry (V. vitis-idaea L.). While these crops are well known throughout the world, in many cases, their individual distributions are quite narrow. Wild lowbush blueberry, for example, is localized in the extreme northeastern United States and maritime provinces of Canada (); bilberry is grown only in a few European countries with an isolated pocket of distribution in the Rocky Mountain region of the USA, and cranberry production, which until recently was confined to the eastern and western coasts of the USA, has recently expanded into higher elevations in South America. The harvested berries are marketed fresh, frozen, and in some cases, sweetened and dried (personal communication, D. Nolte, Decas Cranberry Co.). They are also popular components in bakery items, dried cereals, jams, juices, and numerous related edible products.
Less well-known species of Vaccinium, including wild plantings, are limit-edly distributed in pockets throughout the world. V. pahalae Skottsb., common name ohelo, is typical of this latter category. Ohelo is a creeping shrub which is only known to grow on the main island of Hawaii, in bog-type areas, weathered lava flows, and on mountain slopes. It is expected to hybridize freely with other wild Vaccinium species which colonize this precarious environment. The edible berries range from dark red to pale yellow, and are eaten raw or used in baking. This particular plant is the focus of a rich island folklore, and was considered to be sacred to the volcano goddess Pele. In fact, a legend states that ohelo berries were customarily thrown into the center of volcanic activity to allay the goddess’s wrath; only after this offering was it considered safe to eat the berries.
Production of Bioactive Compounds in Vaccinium Fruits
Members of the genus Vaccinium are primarily grown as a source of edible fruit, but also as landscape ornamentals, and are used to colonize wild areas. In most cases, plants from this genus prefer acid soils and require some inactive dormant cold period in order to successfully produce flowers and fruits. Bog-type environments favor production of some of these fruits (e.g., cranberry and ohelo), and in some cases, production is largely limited to established wild stands, since propagation and new plantings are not easily initiated (wild blueberry). The berries are extracted and marketed as a valuable source of natural anthocyanin pigments for the food-processing industry, as replacements for potentially harmful synthetic pigments and dyes. In cranberry, for example, the waste product of the juicing process (the pomace) can be further extracted as a source of the natural anthocyanin pigments. The flavonoid content (pigments and other polyphenolic compounds) from different species and cultivars has been extensively investigated in an effort to identify donors for valuable extracts. More recently, consumer interest in these species has risen due to increasing evidence for the health protective properties of the berries.
While anthocyanins have most frequently been cited as the bioactive constituents of Vaccinium extracts, considerable evidence has also indicated that the proanthocyanidin fractions possess considerable anticancer and antiradical activity. Mixtures of flavonoids derived from Vaccinium berries may have additive or synergistic biological benefits that cannot be realized from one isolated compound; hence, some of the products derived from the berries are rich in mixtures of pro antho cyanidins and anthocyanins.
Health benefits associated with consumption of some Vaccinium berries have been recognized for centuries, but it is just within the past decade that potent antioxidant, anticancer, cardioprotective, and other bioactive properties have been scientifically demonstrated and widely appreciated. The anthocyanins, the proanthocyanidins, or combinations of these phytochemicals have been reported as the active ingredients from foods and supplements containing Vaccinium spp.. The anthocyanin composition of some of the most important Vaccinium members is given in Table “The anthocyanins in key members of the genus Vaccinium”. The exact pro antho cyanidin composition has not been elucidated for these species. Both leaves and fruits of the bilberry have been known as ingredients of traditional European medicines since the 16th century. Bilberry extracts are rich in up to 15 free anthocyanins (3-O-arabinosides, 3-O-glucosides, and 3-O-galactosides of cyanidin, delphinidin, peonidin, petunidin, and malvidin) as well as associated proanthocyanidins, and are currently marketed through pharmacies in Europe. The antioxidant capacity of the rich flavonoid complement in bilberry extracts effectively inhibits the oxidative modifications of low density lipopro-teins (LDL). Because of this demonstrated capacity, bilberry extracts are consumed in part to inhibit the formation of atherosclerotic plaques in the arterial wall. Research has cited the ability of bilberry anthocyanins to relax coronary artery segments (antagonize contractile responses) as a potential inhibitor of heart disease, and to enhance microvascular blood flow. These same extracts have been lauded for antiulcer and therapeutic activity, and for clinical applications in ophthalmology, including the ability to increase night vision acuity. In all these applications, the anthocyanin pigments are designated as the active principles responsible for bioactivity. Related fruits from other members of the genus are recognized for other miscellaneous health benefits: blueberries and cranberries as sources of antiadhesins (effective in treatment of urinary tract infections); blueberries as a source of cough suppressants and as a diarrhea remedy; cranberries as donors of cardio-protective phytochemicals.
While crude extracts from wild blueberry, cranberry and lingonberry fruits each demonstrated inhibition of the promotion stage of chemically induced carcinogenesis, it was the proanthocyanidin-rich fraction which proved to be most highly anticarcinogenic. Proanthocyanidins are one of the major flavonoid classes found in these fruits, and are associated with, but separate from, the anthocyanin pigments. Further research has recently shown that blueberries, on a fresh weight basis, have the highest antioxidant capacity of all previously tested fruits and vegetables in the typical diet, which is indicative of the ability of these fruits to protect against conditions of neurodegenerative changes with aging, cardiovascular disease, and carcinogenesis. In these tests, the anthocyanin pigments themselves are cited as the active components responsible for antioxidant capacity.
The continuing studies and promising research results on bioactive principles contained in fruits of Vaccinium are expected to further enhance the global market for these berries. Because investigations have elucidated, in part, the identity of chemopreventive compounds such as the flavonoids (in particular, the anthocyanin pigment complex and proanthocyanidins), a new market has developed for extracts in supplement (pill) form. In the US, these supplements are currently marketed through health food stores and groceries, whereas in Europe and Asia, a large market for flavonoid extracts as pharmaceuticals and dietary supplements already exists.
Vaccinium: Summary, Conclusions, and Prospects
At present, the Vaccinium cell culture systems provide useful models for elucidation of the complex anthocyanin pathway, and have potential as vehicles for gene transfer research. Callus and suspension culture systems for flavonoid production were developed for three species (cranberry, ohelo, and bilberry), but only the ohelo system has been scaled-up to 121 bioreactor volumes. Given the increasing public interest in anthocyanins as a source of biomedicinal properties, either in foods or food supplements, these models will be used to characterize the particular species of pigment that confer activity. In particular, issues related to possible additive or synergistic interactions between related phytochemicals (e.g., anthocyanins and associated proanthocyanidins or other flavonoids), which may work in tandem to protect human health, have yet to be fully understood. The simple, predictable, and highly repeatable cell culture production systems for bioactive flavonoid production offer a useful strategy for in depth study of these areas in pharmacological research.
Selections from the book: “Medicinal and Aromatic Plants XII” (2002).