Diets supplemented (1 mmol/kg) with thymol, carvacrol, and beta-ionone
significantly decreased the serum cholesterol levels oi cockerels. Th
ese mevalonate-derived end products of plant secondary metabolism (iso
prenoids) had no impact on two cytosolic prenyl alcohol (and ethanol)
dehydrogenase activities; each treatment increased microsomal geranyl
pyrophosphate pyrophosphatase activity by greater than twofold. The st
ructural diversity of the isoprenoids which suppress cholesterol synth
esis may be reconciled by their ability to increase pyrophosphatase ac
tivity, thus leading to the production of the endogenous, post-transcr
iptional regulator of 3-hydroxy-3-methylglutaryl coenzyme A reductase
activity.