A hairy root culture of Ajugareptansvar. 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