Rowan Berries

Botanical Profile

Note on species delimitation: Sweet orange (Citrus sinensis) and bitter orange (Citrus × aurantium) should be considered separately in botanical and phytochemical statements.

Sorbus aucuparia is a European wild and cultivated tree of the Rosaceae whose bright red pomes have a long ethnobotanical, ecological and food-science significance.

Sorbus aucuparia L. belongs to the Rosaceae and is a characteristic tree species of the temperate and boreal zones of Europe. Its range extends from the Iberian Peninsula through Central and Northern Europe to Western Asia. The species occurs from lowlands to montane and subalpine zones and inhabits woodland margins, clearings, mountain forests, heathlands, bogs and human-influenced sites. Because of its adaptability, rowan is one of the typical pioneer woody plants of the European flora.

Botanically, it is a deciduous small tree or large shrub, usually reaching five to fifteen metres in height. Characteristic features are the imparipinnate leaves with numerous lanceolate leaflets, dense corymb-like white inflorescences and orange to scarlet-red fruits. Botanically, the fruits are pomes and often remain on the tree well into winter. They are an important food source for numerous bird species. The species name aucuparia refers to historical bird-catching and thus to the close relationship between tree, fruit and bird life.

From an ethnobotanical perspective, rowan has a remarkable cultural history. In Scandinavia, the British Isles, the Alpine region and Eastern Europe it was widely regarded as a protective tree and planted near farmsteads. In addition to its symbolic importance, fruits, leaves and bark were used in local systems of use. Today, the fruits in particular are the focus of botanical, food-science and phytochemical consideration.

Phytochemistry

The fruits of Sorbus aucuparia contain a complex spectrum of secondary plant constituents. Polyphenols, organic acids, carotenoids and sugar alcohols are particularly important. Chlorogenic acid, neochlorogenic acid, caffeic-acid derivatives and quercetin and kaempferol glycosides are frequently described. These compounds shape the polyphenolic profile of the fruits.

Parasorbic acid, which occurs in fresh fruits and is partly converted to sorbic acid through suitable processing, is of particular interest. This relationship is well documented in food-science and historical literature and explains the importance of traditional processing methods. The fruits also contain carotenoids such as beta-carotene, which contribute to the orange-red colour, as well as anthocyanins, procyanidins, tannins and aroma components.

Sorbitol occurs in relevant amounts; the name of this sugar alcohol was historically derived from the genus Sorbus. The profile is complemented by carbohydrates, pectins and soluble dietary fibre. Comparative studies within the genus show clear differences between species and populations. Site, degree of ripeness, climate and genetic factors influence composition. Modern HPLC, LC-MS and metabolomic methods now permit more precise characterisation of this variability.

Traditional Uses

Rowan has a long history of use in Europe. The fruits in particular were traditionally collected and used after storage, exposure to frost or processing. In Northern and Central Europe, Scandinavia, Scotland, Eastern Europe and Alpine regions, they were processed into purées, jellies, fruit preparations and preserves.

In addition to culinary use, rowan played a role in many regional traditions. Folklore reports protective symbolism, ideas of fertility and the use of branches or fruits in customs. In many places the tree was regarded as a lucky or protective tree. Historical herbals mention rowan as a native woody plant with diverse uses.

Unlike classic medicinal plants, Sorbus aucuparia has no modern monographs of comparable density to major medicinal drugs. Its importance lies primarily in ethnobotanical, cultural-historical and food-science contexts. Traditional use is treated mainly historically in the scientific literature.

Current Research

Modern research on Sorbus aucuparia focuses on fruit constituents, systematics, ecology and processing. Studies investigate polyphenols, carotenoids, organic acids and other secondary plant constituents using modern analytical methods. Particular attention is paid to polyphenol fractions and their variability between populations and stages of ripeness.

Another field of research concerns the taxonomy of the genus Sorbus. Hybridisation, polyploidy and apomictic reproduction make the group botanically complex. Molecular-genetic studies have led to a more differentiated understanding of relationships.

Ecological studies investigate the importance of the fruits for bird communities and the role of the species in forest ecosystems. Food-science research addresses processing methods, stability of characteristic constituents and quality parameters. Research therefore combines botanical, chemical, genetic and ethnobotanical perspectives.

Sources

• Plants of the World Online. Kew Science. Royal Botanic Gardens, Kew.
• Flora Europaea.
• European Forest Genetic Resources Programme.
• Hager's Encyclopedia of Drugs and Medicinal Substances.
• PubMed-indexed specialist literature on Sorbus aucuparia.
• Specialist literature on the phytochemistry of wild fruits of the Rosaceae.
• Literature on the systematics and evolution of the genus Sorbus.