Preparation of malvalic and sterculic acid methyl esters from Bombax munguba and Sterculia foetida seed oils

Abstract

A method has been developed for the preparation of highly pure malvalic (cis-8,9-methyleneheptadec-8-enoic) and sterculic (cis-9,10-methyleneoctadec-9-enoic) acid methyl esters starting from Bombax munguba and Sterculia foetida seed oils. The methyl esters of these oils were prepared by sodium methylate-catalyzed transmethylation followed by cooling (6°C) the hexane solution of crude methyl esters and separation of insoluble fatty acid methyl esters by centrifugation in the case of B. munguba and by column chromatography in the case of S. foetida. Subsequently, the saturated straightchain fatty acid methyl esters were almost quantitatively removed by urea adduct formation. Finally, methyl malvalate and methyl sterculate were separated from the remaining unsaturated fatty acid methyl esters, in particular methyl oleate and methyl linoleate, by preparative high-performance liquid chromatography on C 18 reversed-phase using acetonitrile isocratically. Methyl malvalate and methyl sterculate were obtained with purities of 95-97 and 95-98%, respectively. JAOCS 75, 1757-1760 (1998). KEY WORDS:Bombax munguba oil, cyclopropene fatty acids, malvalic acid methyl ester, preparative HPLC, Sterculia foetida oil, sterculic acid methyl ester, urea fractionation.Cyclopropene fatty acids are widely distributed in the seed oils of many plant families of the order Malvales (1,2). Small proportions of cyclopropene fatty acids, e.g., malvalic (cis-8,9-methyleneheptadec-8-enoic) and sterculic (cis-9,10-methyleneoctadec-9-enoic) acids, which are present in crude cottonseed oil, are of special interest owing to their harmful biological effects when fed to animals (3-7).The presence of cyclopropene fatty acids in seed oils can be roughly checked by the Halphen test (8). Identification by gas chromatography (GC) and high-performance liquid chromatography (HPLC) analysis (9,10) is difficult, however, because no cyclopropene fatty acid standards are commercially available. This paper presents a simple method for the preparation of both methyl malvalate and methyl sterculate of high purity, which may be useful for GC and HPLC comparison as well as biochemical and enzymatic studies. The starting materials were seeds of Bombax munguba (11) and Sterculia foetida (1,2), which are known to be good sources of cyclopropene fatty acids. EXPERIMENTAL PROCEDURESMaterials. Distilled solvents were used throughout. HPLCgrade acetonitrile was purchased from Rathburn Chemicals (Walkerburn, Scotland). Silica gel, urea, and sodium methylate were products of E. Merck (Darmstadt, Germany). Bombax munguba Mart. seeds were collected at University of Paraiba, João Pessoa, Brazil (11); S. foetida L. seeds were a gift from Professor Helmut K. Mangold, Münster, Germany.Preparation of fatty acid methyl esters (FAME). Seeds of B. munguba (10 g) were ground in an electric coffee grinder and the meal extracted in a Soxhlet extractor for 6 h with 200 mL hexane. The hexane was evaporated and the oil transmethylated with sodium methylate in methanol (11). After addition of...

Urea‐based fractionation of seed oil samples containing fatty acids and acylglycerols of polyunsaturated and hydroxy fatty acids

“…Examples include the isolation of 20:5 5c,8c,11c,14c,17c (eicosapentaenoic acid, or EPA) and 22:6 4c,7c,10c,13c,16c,19c (docosahexaenoic acid, or DHA) from fish oil FFA (2-5), 18:3 6c,9c,12c (γ-linolenic acid, or GLA) from black currant and borage oil FFA (6,7), and 18:3 9c,12c,15c (α-linolenic acid) from linseed oil (8,9). In addition, UC formation effectively discriminated against cyclic FFA, such as malvalic (cis-8,9-methyleneheptadec-8-enoic) and sterculic (cis-9,10-methyleneoctadec-9-enoic) FFA derived from Bombax munguba (cotton) and Sterculia foetida (kapok) seed oils, respectively (10). Most of the cited studies employed the process on a gram scale, although Ackman and coworkers operated on a kilogram (pilot) scale (3).…”

In vitro effects of sterculic acid on lipid biosynthesis inRhodococcus opacusstrain PD630 and isolation of mutants defective in fatty acid desaturation

“…Sterculic acid methyl ester (∼80% pure) was obtained from Reading Scientific Ltd. (Reading, UK). In addition, this inhibitor was gratefully provided by the Institut für Biochemie und Technologie der Fette, Bundesanstalt für Getreide‐, Kartoffel‐ und Fettforschung (Münster, Germany, [17]). It was stored under an atmosphere of nitrogen in a sealed container at −20°C.…”

Comparative studies of immobilized lipase- and acid-catalyzed fatty acid methyl ester synthesis for seed lipid analysis

“…4). It has to be mentioned that base-catalyzed methods (e.g., sodium methoxide) are much more commonly used to prepare methyl esters of cyclopropenoic/acetylenic FA (25,34,35). Although the enzymatic method (method C) was either equally efficient or superior to method B, lipase-catalyzed transesterification was not a promising methods for fatty wax (jojoba oil) ( Table 2).…”