Biosynthesis of oleanolic acid and its glycosides in Calendula officinalis suspension culture

The labeling dynamics of sterols and oleanolic acid (OL) during the incubation with [2-14C] mevalonic acid were examined in Calendula officinalis L. suspension cultures: 1.81 μM (0.4 mg l–1) auxin (2,4-dichlorophenoxyacetic acid, 2,4-D) and 1.85 μM (0.4 mg l–1) kinetin, named 0.4-0.4 culture; and 0.45 μM (0.1 mg l–1) 2,4-D and 2.02 μM (0.5 mg l–1) 6-(γ,γ-dimethylallylamino) purine (2iP), named 0.1–0.5 culture, maintained under light or dark conditions. It was shown that the isoprenoid pathway leading to triterpenoids is operative in all cultures tested. Moreover, it was shown that all OL glucosides and glucuronides, characteristic of leaves of marigold plant, were synthesized after supplying the cultures with [3-3H] OL. The biosynthesis of OL glycosides as well as their release in the extracellular medium was dependent mainly on hormonal conditions of the culture, which can be of biotechnological importance. The biosynthesis and excretion of glucosides were most intense in the 0.1–0.5 culture with no significant effect of light conditions, although in the 0.4–0.4 culture light strongly stimulated the efflux of di-, tri- and pentaglucosides. In turn, glucuronides were synthesized and released in the medium most remarkably in the 0.4–0.4 culture kept in the light and in the dark, although light seemed to stimulate the efflux of monoglucuronide. It seems possible to use the marigold suspension culture as a model system to investigate the regulation of oleanolic glycosides production and excretion.