The Effect of Medium Modification and Selected Precursors on Sterol Production by Short-Term Callus Cultures of Euphorbia tirucalli

Callus tissues of E. tirucalli produce the 4, 4'-dimethyl sterols, euphol and tirucallol. Gas-liquid chromatography was utilized to compare euphol/tirucallol ratios in latex exudate, stem explants and callus tissue. Sterol profiles show that euphol is present in high amounts in latex, but tirucallol predominates in higheramounts in explants and callus indicating synthesis and/or accumulation of tirucallol by cells other than the laticifer cell. Sterol production was significantly enhanced by certain nutrient media, as well as indole-3-acetic acid, and depressed by benzyl adenine. Precursor stimulation of product synthesis was successful only with squalene, which promoted sterol production at 1.0 mg/liter but inhibited cell growth at higher concentrations. L-mevalonic acid and lanosterol promoted neither growth nor sterol production. DL-[214C] mevalonate was used to confirm biosynthesis of sterols in both latex and callus cultures.