Production of iridoid glucosides in cell suspension cultures of Penstemon serrulatus: effects of nutritional factors

The cell growth and iridoid production were studied in suspension cultures derived from anther-callus of Penstemon serrulatus. Penstemide and serrulatoloside were major iridoids produced by the cell cultures. Cells (14 days old)produced up to 7.8 percent of dry weight of penstemide and 5.1 percent of serrulatoloside. However, formation of both iridoids gradually decreased during consecutive growth cycles. It was possible to improve the quantity of penstemide and serrulatoloside in cell cultures by altering the concentrations of some nutritional factors in the medium. The best results were obtained by increasing the concentration of sucrose (to 5 percent or 7 percent); the contents of penstemide and serrulatoloside were 4-fold higher than those obtained in the presence of 3 percent sucrose. Sucrose concentration from 5 percent to 7 percent improved not only the content of iridoids, but also cell growth. Further stimulation of iridoid production was achieved by the selection of high iridoid-producing cell line and transferring the cells to optimized medium.