Eleutherococcus senticosus Rupr. & Maxim is popularly known as Siberian ginseng or Eleuthero is an important medicinal plant belonging to the same Araliaceae family as ginseng (Panax spp.) and was naturally distributed in northeastern Asia and now extensively used in USA (Yat et al. 1998). Roots and rhizome of the plant have long been used as a stimulant and enhance overall resistance to diseases and stress (Farnsworth et al. 1985). Extracts from the plant showed analgesic, anti-inflammatory, antipyretic and diuretic action. Active components of Eleutherococcus species include (1) phenylpropane compounds: synergine = eleuthroside B, sinaptic alcohol, chorogenic acid, caffeic acid derivatives; (2) lignans: syringaresinol-4,4"-O-B-D-diglycoside E (D); syringaresinol-4-O-B-D-glycoside, syringaresinol; (3) coumarins: isofraxidine 7-O glucoside and its aglycone-isoraxidine; (4) polysaccharides; and (5) other compounds, such as oleanic acid, aromatic oils, sugar. These active components showed positive effects on cellular defense and physical fitness in man (Szolomicki et al. 2000). E. senticosus is listed as threatened species because of excessive commercial harvest from natural habitat. Propagation of the plants by seed is difficult because over eighteen months stratification is required for germination of zygotic embryos. So, the plant tissue culture process has been looked at as a potential alternative for the more efficient mass propagation method. Recently, induction of somatic embryogenesis has been reported (Choi et al. 1999). Somatic embryos were successfully cultivated in bioreactors and germinated somatic embryos are used as raw material for medicinal purposes, but the accumulation of physiologically active eleutherosides in germinating embryos was low.
Elicitation has been proved to be effective way to increase secondary metabolite production. A number of elicitors and precursors such as methyl jasmonate (MJ) have been used successfully for enhancing production of secondary metabolites such as saikosaponins, taxoids, plaxitaxel and baccatins, ginsenosides during cell cultures of many plant species (Yukimune et al. 1996; Ketchum et al. 1999; Yu et al. 2000; Aoyagi et al. 2001; Yu et al. 2002; Kim et al. 2004; Thanh et al. 2005). In recent years, we have been searching for a strategy that could significantly affect the accumulation of eleutherosides by focusing on commercially valuable eleutherosides as a research target. In the present study, MJ was employed in embryogenic suspension of E. senticosus in order to examine the impacts on eleutherosides production.
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