| Popis: |
The incorporation of mevalonic acid-2- 14 C into cut flower stalks of Taraxacum officinale L., whose principal sterol and triterpene respectively in the dried form is β-sitosterol and β-amyrin, was studied at intervals of 0·5 hr to 2 weeks. A trace of product possibly identical with lanosterol was indicated by gas chromatography. However, it was only weakly radioactive at all intervals studied, and it was concluded that lanosterol was not an obligatory intermediate in the biosynthesis of β-sitosterol under the conditions of these particular experiments. Several compounds which may be transient 4α-methyl sterols and therefore possible precursors of β-sitosterol were indicated by gas chromatography, but none could be identified with the methyl sterols or triterpenes available as reference compounds. The 14 C-content of β-sitosterol slowly increased to a relatively constant value after 8 hr, thereafter remaining stable. The 14 C-content of β-amyrin, on the other hand, rose slowly to a maximum in about 20 hr and then declined. The data suggest a moderate rate of turnover of β-amyrin. |
