Biosynthesis of 24 beta-alkyl-delta 25-sterols in hairy roots of Ajuga reptans var. atropurpurea
1996
Yagi, T. | Morisaki, M. | Kushiro, T. | Yoshida, H. | Fujimoto, Y.
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 delta 25-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-3 beta-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 24 beta-alkyl-delta 25-sterols in this plant is proposed.
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