Biosynthesis of 24‐methylcholest‐5‐en‐3β‐ol and 24‐ethylcholest‐5‐en‐3β‐ol inZea mays

Abstract
The relative rates of synthesis of 24‐methylcholest‐5‐en‐3β‐ol and 24‐ethylcholest‐5‐en‐3β‐ol inZea mays shoots were determined using [2‐14C]mevalonic acid and [methyl‐14C]methionine as substrates. The 24‐ethylsterol had a higher specific activity and it apparently was synthesized at about 3–4 times the rate of the 24‐methylsterol.1H NMR spectroscopy showed that the 24‐ethylsterol was predominantly the 24α‐epimer but the 24‐methylsterol was a mixture of the 24α‐epimer (30–40%) and the 24β‐epimer (60–70%). The results are discussed in relation to the involvement of Δ24(28)‐, Δ23, Δ25‐ and Δ24(25)‐sterol intermediates in 24‐methyl‐ and 24‐ethylsterol production.