BIOSYNTHESIS OF 24-BETA-ALKYL-DELTA(25)-STEROLS IN HAIRY ROOTS OF AJUGA-REPTANS VAR ATROPURPUREA

A hairy root culture of Ajuga reptans var, atropurpurea contains clero sterol, 22-dehydroclerosterol and cholesterol as its sterol constituen ts. Feeding of [26-, 27-C-13(2)]desmosterol to this culture and C-13 N MR analysis of the resulting biosynthesized sterols showed that the su bstrate was efficiently incorporated into clerosterol and codisterol. Feeding of [26-C-13] and [27-C-13]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-2 7 (exomethylene carbon), respectively, of the two Delta(25)-sterols. F urther, feeding of [24-H-2]desmosterol and H-2 NMR analysis of the pro ducts showed that H-24 of clerosterol and codisterol is derived From H -24 of desmosterol. Finally, [28-C-13]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 biosynth etic mechanism of 24 beta-alkyl-Delta(25)-sterols in this plant is pro posed.