Fatty acids origin determination

Sawfly larvae have been shown to possess a variety of chemical defenses, including many of apparent fatty acid origin. In many cases, the defensive agents were shown to have been sequestered from a plant host." For two species from the genus Hoplocampa, the defensive ventral glandular secretion was determined to comprise of a complex mixture of aromatic compounds and terpenes, as well as several polyacetate-derived components." The polyacetate-derived components were represented mainly by unsaturated aldehydes, such as (E,Z,Z)-2,4,7-decatrienal, but also included acids, esters, and alcohols. 

Lauric diethanolamide is a fairly unreactive substance. A likely approach to the problem of determining low concentrations of this substance involved hydrolysing it to DBA and fatty acid and determining the former by a conventional iodometric method. The lauric diethanolamide content of the extractant could then be calculated from the amount of DBA produced upon complete hydrolysis. It is more appropriate to determine DBA rather than the fatty acid, as it was possible that the extractant could contain fatty acids originating from sources other than hydrolysis of the dialkanolamide, (e.g., free fatty acids or their metal salts or fatty acid esters, all of which might be present in the original polymer). 

The use of both ozonation and ozonolysis is reviewed32. Ozonation leads to ozonide and ozonolysis leads to oxidized fragments, showing the use of both oxidative (AgN03) or reductive [(CH3)2S or PI13P] methods to produce the FAME (fatty acids methyl esters) that by subsequent GC analysis enabled determination of the position of the double bonds in the original molecule (equations 2-4). 

Unsaturated acids may be split chemically at their double bonds. Permanganate-periodate oxidation has been used to produce the corresponding carboxylic acids, while an alternative technique of ozonolysis results in the formation of aldehydes and aldehyde esters. All these reaction products may be identified by GLC and the information used to determine the position of the double bond in the original fatty acid. 

Between 1906 and 1908 the breakdown of fatty acids to acetone was detected by Embden in perfused livers. Only fatty acids with even numbers of carbon atoms produced this effect. The acetone was postulated to have originated from acetoacetate. For the next 30 years the 6-oxidative route of fatty acid oxidation was generally unchallenged. By 1935-1936 however much more accurate determinations of the yields of acetoacetate per mole of fatty acid consumed (Deuel et al., Jowett and Quastel) indicated convincingly that more than one mole of acetoacetate might be obtained from 6C or 8C fatty acids. (Octanoic acid was often used as a model fatty acid as it is the longest fatty acid which is sufficiently soluble in water at pH 7.0 for experimental purposes.) The possibility had therefore to be entertained that 2C fragments could recondense (MacKay et al. 1942). 

Colorimetry. Copper (Duncombe 1963 Koops and Klomp 1977) or cobalt (Novak 1965) soaps of long-chain fatty acids (>C12) are soluble in chloroform and can be determined quantitatively by colorimetric determination of the extracted metal. Shipe et al. (1980B) have recently modified the original copper soap method to make it simpler, more rapid, and adaptable to automatic equipment. 

Commercial crude lecithin is a hrown to light yellow fatly substance with a liquid to plastic consistency. Its density is 0.97 g/niL (liquid) and 0.5 g/mL (granule). The color is dependent on its origin, process conditions, and whether it is unbleached, bleached, or Altered. Its consistency is determined chiefly by its oil. free fatty acid, and moisture content. Properly refined lecithin has practically no odor and has a bland taste. It is soluble in aliphatic and aromatic hydrocarbons, including the halogenated hydrocarbons however, it is only partially soluble in aliphatic alcohols. Pure phosphatidylcholine is soluble in ethanol,... 

Our present efforts are being devoted to studying pea lipides in situ, in the hope of determining whether hormone activation by lipide substances is a natural method of growth regulation. Gas chromatography has already confirmed that our original active pea extract is a mixture of conventional fatty acid esters. 

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