| Abstrakt: |
The sterol compositions of roots, leaves, stems, flowers and vegetatively cloned plantlets of Kalanchoe daigremontianawere examined by TLC, GLC, HPLC, mass and 1H NMR spectroscopy. Fourteen Δ5-sterols were identified. They were cholesterol, 24(28)-methylenecholesterol, 24-methyl-23-dehydrocholesterol, 24-methyl-24-dehydrocholesterol, 24α-methylcholesterol, 24β-methylcholesterol, 24β-ethyl-22,25(27)-bis-dehydrocholesterol, 24-dimethyl-25(27)-dehydrocholesterol, 24-dimethyl-25(27)-dehydrocholesterol, 24β-ethyl-25(27)-dehydrocholesterol(clerosterol, 24-ethyl-24-dehydrocholesterol (24-ethyldesmosterol), trans-24-ethylidenecholesterol (isofucosterol), 24α-ethylcholesterol (sitosterol), 24α-ethylcholesta-5,22-dienol (stigmasterol). While sterols with doubly alkylated C-24 side chains predominated the sterol mixture in all tissues examined, substantial differences in the configurational purity of the C-24 alkyl group were noted. For instance, leaves produced primarily 24β-ethyl sterols, stems and flowers produced about equal proportions of 24α-and 24β-ethyl sterols and roots produced primarily 24α-ethylsterols. Kinetics of the biosynthesis of sterols using [2-14C]acetate fed to plantlets for 216 hr where no 24α-ethyl sterols were detected indicated that the relative rates of synthesis for cholesterol (a trace sterol component) was very rapid compared with the slow turn-over rates of the bulk Δ22-24β-alkylated sterols. |
