Triterpenoid biosynthesis in tissue cultures of Glycyrrhiza glabra var. glandulifera.

The incorporation of [1-(14)C]acetate and [2(14) C]mevalonate into free and esterified triterpen-3-ols was examined in original plant organs and tissue cultures of Glycyrrhiza glabra var. glandulifera. Both substrates labeled β-amyrin, an oleanane-type triterpene, and cycloartenol and 24-methylenecycloartanol, both of which are intermediates of phytosterol biosynthesis. The label in esterified triterpenes was distributed mainly in phytosterol intermediates, but not in β-amyrin. The ratio of βamyrin formation among the three triterpenes from [2-(14)C]mevalonate was relatively high in stolon segments and in root cultures, but negligible in callus cultures. Administration of a specific inhibitor of squalene-2, 3-epoxide:cycloartenol (lanosterol) cyclase caused a marked increase of β-amyrin synthesis in root suspension cultures, and of 24-methylenecycloartanol synthesis in cell suspension cultures, from [2-(14)C]mevalonate.