Monohydric phenolic lipids

Table 1. Occurrence of monohydric phenolic lipids (cardanol type)...

Besides typical cardanol-like structure, Sleeper and Fenical have identified in 1977 navenone, an alkylphenol derivative as a component of trail pheromone of the mollusk Navanax inermis [27]. Another alkylpheno lie derivative, plakinidone, has beed isolated in 1991 from a Caribbean sponge Plakortis angulospiculatus [26]. In 1995 the carboxylic acid derivative of alkylphenol - elenic acid was isolated from the Indonesian sponge Plakinastrella [25]. The structures and formulas of known monohydric phenolic lipids are presented in Fig. (1). 

ABSTRACT This review is concerned with non-isoprenoid phenolic lipids typified by compounds biosynthesised by the polyketide pathway. Botanical, biological and entomological sources of such phenolic lipids are described which contain monohydric phenols, notably cardanol and relatives, dihydric phenols such as cardols, alk(en)ylresorcinols,urushiols and phenolic acids, particularly anacardic acids. Some recently investigated mixed types of dihydric phenolic lipids are included. Separatory methods are briefly reviewed. Synthetic methods for the saturated and unsaturated members of the three main classes of interest in structure/activity studies are summarised. Biological properties of members of the three main classes are given and discussed. 

The phenolic lipids occur in many different botanical families, notably in the Anacardiaceae, and they exist in tropical, sub-tropical, temperate climates in certain trees, shrubs and plants. In addition they are found in some bacterial and antibiotic sources and in certain insects. As benzenoid derivatives they are conveniently. although perhaps artificially, grouped for chemical purposes into phenolic acids, polyhydric, dihydric and monohydric phenols. Tables 13.1, 13.2 and 13.3 and the collections of formulae summarise some of the the information on these products. The structural types are extensive. For example, (5-phenylalkylphenols have been isolated from several different sources and included are certain bridged biphenyls from Grevillea and Betulaceae species. 

An inherent problem in the usage of phenolic lipids, particularly in surface coatings, is the discolouration which can impair products. Apart from colourants arising from the solvent action of CNSL on the shell in the industrial process, the dihydric phenols In CNSL notably the minor component 2-methylcardol (ref. 200) more than cardol appear to be the cause of this deterioration rather than the monohydric member, cardanol. The usage of purer cardanol, or the less unsaturated material by semi-hydrogenation or chemical reduction, as well as the Incorporation of an antioxidant are methods for colour stabilisation (ref. 277). Antioxidant applications and pharmaceutical uses of CNSL and its component phenols are referred to in the next section. 

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