PHYTOALEXIN ELICITORS AS INDUCERS OF MEDICINAL CONSTITUENTS IN SOME PLANT CELL CULTURES.

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Cell wall fragment of phytopathogenic fungi or plants acts as a signal molecule and induces biosynthesis of phytoalexins at transduction level. Phytoalexins are produced in large quantities by plants only when they are infected by pathogens. Structure of phytoalexins diverses but usually possesses the same skeleton as normal metabolites. In other words phytoalexins share most of their biosynthetic routes with normal metabolites. These facts suggest that the addition of elicitors to the plant cell cultures might increase the production of useful metabolites which can not be achieved under normal culture conditions. In this study, effects of various elicitors on the production of medicinal constituents in cell cultures of Pueraria lobata and Ephedra distachya were investigated. Cell cultures of Pueraria lobata produce daidzein and its glycosides under normal conditions. Addition of the glycoprotein fraction of Phytophthora megasperma increased the production of daidzein and its glycoside … More s by 5 to 7 folds, and induced the biosynthesis of pterocarpan phytoalexin tuberosin in large amounts. On the contrary, the glucan fraction of the same fungi which has been claimed to be the most active elicitor in many Leguminous plants showed almost no effects indicating that even the plants belonging to the same family respond differently to the same elicitor. Yeast extract and cell wall fragments of Pueraria lobata released by pectinase showed the similar effects and increased the production of isoflavonoids through activation of biosynthetic enzymes. Production of three different types of daidzein dimer were induced by these elicitors. Considering that yeast has been used as foods and or food additives and its availability, yeast extract has great advantages over other elicitors in industrial applications. Some elicitors of different origin were tested for their activation effects on the biosynthesis of ephedra bases in cell cultures of E. distachya. No significant increase of alkaloid production was observed though unidentified yellow pigment was induced with yeast extract. Lack of antibiotic activity of ephedra bases might account for this observations. Less