INVESTIGATIONS ON THE Δ23-, Δ24(28)- and Δ25-STEROLS OF ZEA MAYS

Article abstract of DOI:10.1016/0031-9422(84)83081-2

The sterols of Zea mays shoots were isolated and characterized by TLC, HPLC, GC/MS and 1H NMR techniques.In all, 22 4-demethyl sterols were identified and they included trace amounts of the Δ²³-, Δ²⁴- and Δ²⁵-sterols. 24-methylcholesta-5,E-23-dien-3β-ol, 24-methylcholesta-5,Z-23-dien-3β-ol, 24-methylcholesta-5,25-dien-3β-ol 24-ethylcholesta-5,25-dien-3β-ol and 24-ethylcholesta-5,24-dien-3β-ol.In the 4,4-dimethyl sterol fraction, cycloartenol and 24-methylenecycloartanol were the major sterol components but small amounts of the Δ²³-compound, cyclosadol, and the Δ²⁵-compound, cyclolaudenol, were recognized.These various Δ²³- and Δ²⁵-sterols may have some importance in alternative biosynthetic routes to the major sterols, particularly the 24β-methylcholest-5-en-3β-ol component of the C₂₈-sterols.Radioactivity from both <2-14C>MVA and methionine was incorporated by Z. mays shoots into the sterol mixture.Although 24-methylene and 24-ethylidene sterols were relatively highly labelled, the various Δ²³- and Δ²⁵-sterols contained much lower levels of radioactivity, which is possibly indicative of their participation in alternative sterol biosynthetic routes. (24R)-24-Ethylcholest-5-en-3β-ol (sitosterol) had a significantly higher specific activity than the 24-methylcholest-5-en-3β-ol indicating that the former is synthesized at a faster rate.Key Word Index -- Zea mays; Gramineae; sterols; sterol biosynthesis; cyclolaudenol; cyclosadol; 24-methylene-cycloartanol; 24-methylcholesta-5,E-23-dien-3β-ol; 24-methylcholesta-5,24(28)-dien-3β-ol; 24-methylcholesta-5,25-dien-3β-ol; 24-methylcholest-5-en-3β-ol; 24-ethylcholest-5-en-3β-ol.