Intermediates of tocopherol biosynthesis in the unicellular alga Scenedesmus obliquus. The presence of three isomeric methylphytylbenzoquinones

Abstract

Three isomers of methylphytylbenzoquinone have been isolated from lipids of the unicellular alga Scenedesmus obliquus, the most abundant being 2-methyl-6-phytylbenzoquinone (65% of the total). The 2-methyl-3-phytyl and 2-methyl-5-phytyl isomers amounted to 8 and 27% respectively. Previously problems have been encountered in the separation of the 3-phytyl and the 6-phytyl isomers, but in the present study it was found that they separated readily as quinols. Phytyl plastoquinone was also found and the relevance of these compounds to the biosynthesis of alpha-tocopherol is discussed. As well as phylloquinone, a hydroxyphylloquinone was detected, and studies indicated that it is the 5′ carbon atom to which the hydroxy group is attached. Such a compound has been found by workers using other unicellular algae.