Hydroxyfatty acids

FIGURE 9.4 TLC-blotting/SIMS of various glycosphingolipids. (A) TLC profile of the separated glycosphingolipids, (B) MS profiles obtained by TLC-blotting/SIMS (a) spectrum of sulfatide peaks at m/z 862, 876, 890, 906, and 918 are molecular ions with different fatty acid species indicated in the figure (asterisks are peaks of triethanolamine as matrix) (b) spectrum of Gb Cer peaks at m/z 1309 and 1337 are molecular ions with different fatty acid species as indicated (c) spectrum of G peaks at m/z 1151, 1235, and 1263 are molecular ions with different fatty acid species as shown. Abbreviations LCB — long chain base, FA — fatty acid, hFA — hydroxyfatty acid. Hex — hexose, HexNAc — /V-acetylhexosamine. (From Taki, T. et al.. Anal. Biochem., 225, 24—27, 1995. With permission.) Continued. 

The conquest of the land by plants necessitated the development of a coating, the cuticle, that would reduce water loss. Suberin and cutin vary in their proportion of fatty acids, fatty alcohols, hydroxyfatty acids, and dicarboxylic acids. The cuticle is synthesized and excreted by the epidermis of aerial portions of the plant, such as the primary stems, leaves, flower organs, and fruits. The two major hydrophobic layers that contribute to the cuticle are composed of phenolic molecules combined with lipid polymers. Cutin is a polymer found in the outer cell wall of the epidermis, which is... 

As a result of the action of lipoxygenases [3], hydroxyfatty acids and hydroperoxyfatty acids are formed from arachidonate, from which elimination of water and various conversion reactions give rise to the leukotrienes. The formulae only show one representative from each of the various groups of eicosanoids. 

Alcohol + acid Hydroxyfatty acid Alcohol + cofactor Alcohol + cofactor... 

In addition to carboxylic acid salts, other effective lubricity additives that the chemist will work with are esters of hydroxyfatty acids, non-ionic surface agents, dibasic acids, and additives from substituted fatty acids. Although this is not a complete list, its contents are the most effective from a cost perspective and are typically used in the industry. The oleate of ricinoleic acid dimer is an example of a hydroxyfatty acid prepared from ricinoleic acid oligomer with acid chloride in the presence of pyridine, as shown in Figure 2.4. 

Cutin. Structural component of the outer lipophilic protective layer (cuticle) of the aerial parts of plants, especially leaves. Suberin serves similar functions in roots and bark. C. is a natural polyester, formed enzymatically from hydroxyfatty acids with 16 and 18 C atoms. o+Hydroxy- and dihydroxyfatty acids, e.g., 10,16-dihydroxypalmitic acid, as well as epoxy- and oxofatty acids, and a,o>-dicarboxylic acids are the main components of cutin. Cutinases (C.-cleaving enzymes) occur especially in pollen and in plant-pathogenic fungi, e.g., Fusarium solani (while rot in potatoes). 

TLC systems which can be used for preparative purposes are many and varied. Useful examples are listed in Kates (1972), Christie (1982), Stahl (1969) and Kundu (1981b). It is usually necessary to use TLC to finally purify a lipid which has been obtained by column chromatography. TLC is also useful to separate ceramides with normal fatty acids from those with hydroxyfatty acids (Rouser et al, 1969). 

The interest in suberin lies in the fact that it constitutes an abundant source of dicarboxylic acids and homologous mid-chain dihydroxy or epoxy derivatives [14]. Apart from this source, these compounds are not very abundant in nature. Thus, hydroxyfatty acids can only be additionally found in exploitable amounts in the seed oils of Ricinus communis (castor oU) and Lesquerella spp., as well as in the extracellular aliphatic polyester covering most of the aetiai surfaces of plants, known as cutin [41]. 

Under alkaline hydrolysis conditions, the ensuing free w-hydroxyfatty acids and a,(rt-dicarboxylic acids are obtained, with extensive cleavage of epoxy functionalities to the corresponding vic-diols. It has been claimed, however, that when the reaction is carried out for 15 min using KOH in ethanol water 9 1 v v, total depolymerization occurs with preservation of the epoxy functionalities [63], a feature that can be interesting for some polymer applications. 

As in the case of total suberin contents in its natural precursors, the monomer composition and abundance are also highly variable, but in general the most abundant families of compounds are m-hydroxyfatty acids, followed by a,w-dicarboxylic acids and by smaller amounts of fatty acids, aliphatic alcohols and aromatic compounds. 

The biologically produced biopolyesters comprise a complex class of polyox-oesters [1-4] The majority of prokaryotes synthesize PHB and/or other PH As composed of medium-chain length (/ )-3-hydroxyfatty acids (6-14 carbon atoms) as reserve material. These polyesters are deposited as spherical water-insoluble inclusions in the cytoplasm (Figure 3.2). The biopolyester comprises the core of the granule. More than 150 different hydroxyalkanoic acids are known to occur as parts of PHAs implying that the respective CoA thioester are accepted as substrates by the PHA synthases (Figure 3.1). Some representative constituents are displayed in Figure 3.3. 

MicrobiaUy synthesized rhamnolipids are a mixture of a number of analogous molecules. The four most important ones comprise either one (mono-rhamnolipids) or two (di-rhamnolipids) rhamnose molecules attached to one or two saturated P-hydroxyfatty acids Cg to Cjg (Figure 14.1). 

Table 1. Relative activity of fatty alcohols or 0)-hydroxyfatty acids in the feruloyl-CoA transferase assay...

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