11 Analysis of Isoprenoid Quinones

Abstract

This chapter discusses analysis of isoprenoid quinones. The respiratory quinones represent an important group of isoprenoid lipids that occur in the cytoplasmic membrane of most prokaryotes. Two major structural groups of bacterial isoprenoid quinones can be recognized: the naphthoquinones and benzoquinones. Naphthoquinones can be divided further into two major types: phylloquinones and menaquinones. In choosing the methods to be employed for the extraction and purification of menaquinones, ubiquinones, and related quinones one must take into account the susceptibility of these compounds to degradation. Isoprenoid quinones are quite rapidly photo-oxidized in the presence of oxygen and strong light. They are also particularly susceptible to alkaline conditions (the last limitation rules out alkaline saponification). Thus, it is preferable to conduct extraction and subsequent purification procedures fairly rapidly, avoiding extremes of pH and strong light. The composition of natural mixtures of bacterial quinones can be investigated using partition chromatography. Separation of compounds by partition chromatography is generally on the basis of relative solubilities, which in the case of homologous series such as ubiquinones and menaquinones is determined by the length and degree of hydrogenation of the multiprenyl side chain. © 1985, Academic Press Inc. (London) Ltd.