Roseroot (Rhodiola rosea L.): Effect of Internal and External Factors on Accumulation of Biologically Active Compounds

Abstract

Roseroot (Rhodiola rosea L.) is a perennial that grows wild in the mountains of Siberia, Central Europe and North America. Its underground organs (rhizomes with roots) are used as a medicinal raw material; the plant is considered to be one of the most active adaptogens. The most important biologically active constituents of the raw material are phenolic compounds, including tyrosol and its glycoside salidroside, and trans-cinnamic alcohol derivatives (rosavin, rosarin and rosin). The results of several years of study carried out at Warsaw University of Life Sciences - SGGW in Poland indicate a high intraspecific variability concerning accumulation of these compounds. It was also stated that both the weight of the underground organs of roseroot and the content of active compounds changes during plant development. The mean weight of air-dry rhizomes with roots of plants grown in central Poland increased by up to 120 g per plant in the 5th year of plant vegetation. In the 6th year the symptoms of plant aging were observed – the oldest, central part of rhizome decayed and the rhizome divided into many smaller parts characterised by lower content of salidroside and rosavin. The yield and quality of roseroot raw material was also significantly affected by climatic and soil conditions. Plants grown in central Poland were characterised by higher weight of underground organs but lower content of rosavin and salidroside in comparison with those grown in southern Poland (mountain area). Post-harvest treatment of the raw material (stabilisation and extraction method) distinctly affected the quality of the obtained extracts. Both convection drying at 80ºC and lyophilisation are good methods of stabilisation of the roseroot raw material. Periodical extraction with ultrasound, and continuous exhaustive extraction using both methanol and 75 % ethanol as extraction media allow to get extracts of comparable content of determined phenolic compounds.