Biosynthesis of 24β-alkyl-Δ25-sterols in hairy roots of Ajuga reptans var. atropurpurea

Article abstract of DOI:10.1016/0031-9422(95)00766-0

A hairy root culture of Ajuga reptans var. atropurpurea contains clerosterol, 22-dehydroclerosterol and cholesterol as its sterol constituents. Feeding of [26-, 27-¹³C₂]desmosterol to this culture and ¹³C NMR analysis of the resulting biosynthesized sterols showed that the substrate was efficiently incorporated into clerosterol and codisterol. Feeding of [26-¹³C] and [27-¹³C]desmosterols revealed that the C-24 alkylation takes place in a highly specific manner wherein the 26- and 27-methyl groups of the substrate becomes C-26 (vinyl methyl) and C-27 (exomethylene carbon), respectively, of the two Δ²⁵-sterols. Further, feeding of [24-²H]desmosterol and ²H NMR analysis of the products showed that H-24 of clerosterol and codisterol is derived from H-24 of desmosterol. Finally, [28-¹³C]ergosta-5,24(28)-dien-3β-ol was shown to be converted into clerosterol and 22-dehydroclerosterol, but not into codisterol. On the basis of these data, possible biosynthetic mechanism of 24β-alkyl-Δ²⁵-sterols in this plant is proposed. Copyright