Sur l'origine de la double liaison en position 22,23 des phytostérols

The radioactivity of the propionate of α-spinasterol-3 3H (I) is incorporated with a yield of 0·7 per cent in the Δ5-sterols of tobacco leaves (Nicotiana tabacum). β-Sitosterol (II) is much more radioactive than stigmasterol (III). These results indicate that β-sitosterol is the precursor of stigmasterol, i.e. that the double bond in the 22 position is introduced by desaturation of the side chain.