Raspberry

Botanical Profile

Rubus idaeus is the red raspberry, a perennial shrub of the Rosaceae. Botanically and as raw materials, the aromatic aggregate fruits and tannin-rich leaves are especially important; the two plant parts differ substantially in composition, sensory properties and use context.

Rubus idaeus L. is a deciduous perennial shrub with a persistent root system and newly formed canes each year, usually flowering and fruiting in their second year. The species is distributed across large parts of the temperate Northern Hemisphere and prefers forest margins, clearings, hedges, disturbed woodland sites and cool, humus-rich habitats. Characteristic features are compound leaves, usually with three to five leaflets, prickly to bristly canes, white five-petalled flowers and an aggregate fruit composed of numerous small drupelets. The ripe raspberry separates from the cone-shaped receptacle and is therefore hollow inside; this morphologically distinguishes it from many blackberry forms. Fruits are used fresh, frozen, dried, as juice, purée, fruit powder or aromatic fruit raw material. The leaves are described as raspberry leaf or Rubi idaei folium and differ clearly from fruit preparations botanically, sensorially and phytochemically.

Phytochemistry

The fruits of Rubus idaeus contain sugars, organic acids, soluble and insoluble fibre, minerals, volatile aroma compounds, anthocyanins, flavonols and ellagitannins. Anthocyanins and a complex aroma pattern of esters, ketones, aldehydes and terpenoids are particularly important for colour and sensory character. Ellagic-acid derivatives and sanguiin H-6 are among the typical raspberry polyphenols. The leaves have a different phytochemical pattern. They contain primarily tannins, flavonoids, phenolic acids and other polyphenolic fractions. Colour, odour, astringency and extract composition vary with harvest time, drying, cut size and extraction process. A raspberry-fruit extract is therefore not analytically, sensorially or as a raw material equivalent to a raspberry-leaf extract.

Traditional Uses

Raspberry has long been a gathered, garden and cultivated plant in Europe and Asia. The fruits were traditionally eaten fresh, preserved, dried or processed into syrup, juice, purée, vinegar, liqueur or baking ingredients. Raspberry leaves were used in the European herbal tradition as a tannin-rich leaf drug and are documented in phytotherapy as Rubi idaei folium. In folk contexts, raspberry leaves appear particularly in women's herbal teas, mucosal and mouth rinses, and simple household remedies. These historical and traditional uses must be distinguished from modern health-related statements and require clear assignment of the plant part used.

Current Research

Current research on Rubus idaeus addresses cultivar differences, polyphenol patterns, anthocyanins, aroma formation, storage stability, processing and the utilisation of side streams from fruit processing. Fruit-chemistry studies focus particularly on ellagitannins, anthocyanins, organic acids and volatile aroma compounds. In leaves, tannins, flavonoids and characterisation of traditional herbal preparations are central. For scientific assessment, it is crucial to establish whether fruit, leaf, pomace, juice, powder, extract or an isolated polyphenol fraction was investigated; findings from different plant materials are not readily interchangeable.

Sources

• Kew Science, Plants of the World Online: Rubus idaeus L.
• EMA/HMPC: Final Community herbal monograph on Rubus idaeus L., folium, EMA/HMPC/44211/2012.
• Specialist literature on raspberry fruits, anthocyanins, ellagitannins and raspberry-leaf polyphenols.