Dihydroxypalmitic acid

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). 

The major hydroxy fatty acids in plants have an ft>-OH and an in-chain OH group (e.g. 10,16-dihydroxypalmitic acid). Their synthesis seems to involve cw-hydroxylation with NADPH and O2 as cofactors followed by in-chain hydroxylation using the same co-substrates. If the precursor is oleic acid then the double bond is converted to an epoxide which is then hydrated to yield 9,10-hydroxy groups. These conversions involve CoA esters. In-chain plant hydroxylase is sensitive to inhibition by o-phenanthroline and by CO in a reaction that is reversed by 420 60 nm light (Kolattukudy, 1980). 

Cutin is composed of chiefly a Cig family and/or a Cig family of monomers (Fig. 9). The usual meyor components of the former are palmitic acid, 16-hy-droxypalmitic acid, and 10,16-dihydroxypalmitic acid and/or its positional isomers, in which the midchain hydroxyl group is at C-9, C-8, or C-7 (Kolat-tukudy, 1977b Brieskom, 1978). The dihydroxy acid from papaya and tomato cutin showed a plain-positive rotation, and therefore the L configuration has been assigned to this major cutin monomer (Espelie and... 

Walton T J, Kolattukudy P E 1972 Enzymatic conversion of 16-hydroxypalmitic acid into 10,16-dihydroxypalmitic acid in Vida faba epidermal extracts. Biochem Biophys Res Commun 46 16-21... 

Viciafaba leaf cuticle is an amorphous type cuticle [10]. Waxes have been described by Kolattukudy [11]. Cutin studied by Kolattukudy and Walton [12]. is mostly composed of 85% 9,16 or 10,16-dihydroxypalmitic acid, 7% 16-hydroxypalmitic acid and contains minor percentages of palmitic acid, stearic acid and oleic acid (8 %). 

Composition. Shellac is primarily a mixture of aUphatic polyhydroxy acids in the form of lactones and esters. It has an acid number of ca 70, a saponification number of ca 230, a hydroxyl number of ca 260, and an iodine number of ca 15. Its average molecular weight is ca 1000. Shellac is a complex mixture, but some of its constituents have been identified. Aleuritic acid, an optically inactive 9,10,16-trihydroxypalmitic acid, has been isolated by saponification. Related carboxyflc acids such as 16-hydroxy- and 9,10-dihydroxypalmitic acids, also have been identified after saponification. These acids may not be primary products of hydrolysis, but may have been produced by the treatment. Studies show that shellac contains carboxyflc acids with long methylene chains, unsaturated esters, probably an aliphatic aldehyde, a saturated aliphatic ester, a primary alcohol, and isolated or unconjugated double bonds. 

The relative and absolute configuration of 35,125-dihydroxypalmitic acid, a constituent of the Ipomea operculata M. resin, was confirmed by synthesis starting with dimethyl L-malate (35). An efficient synfliesis of (55)-hydroxy-20 4(6 ,8Z,l 1Z,14Z) was accomplished by the coupling of two readily accessible synthons, methyl (55)-hydroxy-7-iodo-heptanoate and 4Z,7Z- tridecadien-l-yne (36). A highly stereoselective synthesis of P-dimorphecolic acid, (95)-hydroxy-18 2(10.E,12 ), has been reported the synthesis features a diastereoselective reduction of a keto intermediate [4] in which the tricarbonyliron lactone tether induces a 1,5-transfer of chirality followed by a stereoselective decarboxylation to create all of the stereochemical ele-... 

Dihydroxypalmitic acid. Operculinolic acid. Con-volvulinolic acid... 

Convolvulinolic acid = (115)-hydroxytetradecanoic acid = 11-hydroxymyristic acid Ipolearic acid = (35,115)-dihydroxyhexadecanoic acid = 3,11-dihydroxypalmitic acid Ipurolic acid = (35,11 -dihydroxytetradecanoic acid = 3,11-dihydroxymyristic acid Jalapinolic acid = (115)-(+)-hydroxyhexadecanoic acid = 11-hydroxypalmitic acid Operculinolic acid = 3,12-dihydroxyhexadecanoic acid = 3,12-dihydroxypalmitic acid Turpetholic acid A = 3,12-dihydroxypentadecanoic acid Turpetholic acid B = 4,12-dihydroxypentadecanoic acid... 

Turpetholic acid C = 4,12-dihydroxyhexadecanoic acid = 4,12-dihydroxypalmitic acid Sugars (monosaccharides). ... 

Buchanan, J. F., and Fulco, A. J. 1978. Formation of 9,10-Epoxypalmitate and 9,10-Dihydroxypalmitate from Palmitoleic Acid by a Soluble System from Bacillus megaterium. Biochem. Biophys. Res. Comm., 85,1254-1260. 

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