Double bond location in polyenoic fatty esters through partial oxymercuration

A rapid micro-procedure has been developed to locate double bonds in fatty acid methyl esters containing from one to four double bonds. Reaction of the ester with an equal molar amount of mercuric acetate in methanol and reduction with sodium borohydride, followed by hydrogenation, produce a mixture of monomethoxy alkanoates. The mass spectrum of this mixture is simpler and more definitive than that from the completely methoxylated polyenoate. Only one methoxyl group is present per molecule, and the mass spectrum of the mixture is indicative of all olefinic positions. Four intense ions are observed for all double bonds examined, except Δ3, where the double bond is represented, by only two ions. Hydrogenation in a gas chromatograph reduces total analysis time to 1 hr. Presented at the AOCS Meeting, Cincinnati, September 28–October 1, 1975.     

Unsaturated C18 α-hydroxy acids inSalvia nilotica

The oil ofSalvia nilotica Jacq. (Labiatae) seed contains 0.6% α-hydroxyoleic, 4.2% α-hydroxylinoleic, and 5.4% α-hydroxylinolenic acids. The first two have not been found previously in seed oils. In addition to the common fatty acids, also identified were small amounts of three unsaturated C₁₇ acids and one branched chain C₁₇ acid. Methyl esters of the component fatty acids were fractionated by both column and thin-layer chromatography. These esters were identified by combination of gas chromatography, GC-mass spectrometry, ozonolysis-GC, infrared, and nuclear magnetic resonance.     

Supercritical fluid chromatographic analysis of new crop seed oils and their reactions

Supercritical fluid chromatography (SFC) with an open tubular column of nonpolar stationary phase separated triglycerides from crambe, meadowfoam,Euphorbia lagascae, and vernonia oils based on their molecular weight. The triglyceride compositions were consistent with the literature. SFC proved also to be a valuable tool in analyzing lipase-catalyzed transesterification reactions where lesquerella oil and estolides were among the substrates employed. Analyte molecular weights could be estimated from a retention time- (or elution density-) molecular eeight calibration curve. An increase in isothermal column temperature during SFC pressure or density programming improved the resolution of high-molecular-weight (>600 Da) analytes but yielded poorer resolution for analytes of molecular weight <200. A simultaneous pressure and temperature ramping program proved superior in enhancing resolution in several instances. Presented at the AOCS Annual Meeting & Expo, May 1995, San Antonio, Texas. Retired     

Effectiveness of several polyunsaturated seed oils as boll weevil feeding deterrents

Prompted by the previous discovery that (9Z,11E,13E)-9,11,13-octadecatrienoic acid (α-eleostearic acid) was one of the compo-nents responsible for the boll weevil feeding deterrency of tung oil, the seeds of 11 other plant species were extracted with pentane and the oils were evaluated for their feeding deterrency in the laboratory. The oils ofCalendula suffruticosa, Centrantbus macro-siphon, Jacaranda mimosifolia andMomordica cochincbinenis were effective feeding deterrents for the boll weevil.     

On-line chemical database for new crop seeds

Since the 1950s, a database of the chemical composition of seeds, collected throughout the world, has been generated at the National Center for Agricultural Utilization Research. Information contained in the database is primarily selected chemical and physical properties of seed oils. Over more than 38 years, 15,738 accessions of 7,924 species of 2,339 genera from 225 families were collected and analyzed. This database is now accessible on the Internet at http://www.ncaur.usda.gov/nc/ncdb/search.html.ssi. This paper gives an overview of the database, describes the information available, and illustrates how to do searches. Retired USDA/ARS.     

TheTrans-6 fatty acids ofPicramnia sellowii seed oil

The C₁₈ monoenoic acids inPicramnia sellowii Planch. seed oil include bothcis-andtrans-6-octadecenoic acids, as well as oleic acid. The hexadecenoic acids are also thecis- andtrans-Δ6-isomers, and the eicosenoic acids have Δ6-unsaturation of undetermined geometric configuration. The C₁₈ polyenoic acids detected are 9,12- and 6,9-octadecadienoic and 9,12,15- and 6,9,12-octadecatrienoic acids. Partial investigation of another species,P. pentandra Sw., revealed its oil to have a similar fatty acid composition. Presented in part at AOCS Meeting, New York, October 1968. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Preparation of meadowfoam dimer acids and dimer esters,and their use as lubricants

Meadowfoam dimer acids have been prepared in a thermal clay-catalyzed reaction. Reaction conditions have been optimized, and yields of 44% were obtained with 2% water and 6–8% of an acid-washed montmorillonite clay, based on the meadowfoam fatty acids. Purity of the distilled dimer acids was 79–89% with most of the remaining 11–22% being residual mono- and tribasic acids. Dimethyl, di-(2-ethylhexyl), and di-n-butyl meadowfoam dimer ester derivatives were also prepared. Color, viscosity, and wear-preventive characteristics of the meadowfoam dimer acids and dimer ester derivatives were compared to those of commercial dimer acids and dimer esters. The viscosity of the meadowfoam dimer acids is similar to that of Empol® 1010, which is also derived from a highly monounsaturated fatty acid source. Viscosities of the meadowfoam dimer esters were also comparable to those of commercial dimer esters. Wear prevention characteristics, as determined by the four-ball test method, of the meadowfoam dimer acids and dimer esters were similar to those of the commercial products. In one case, the di-n-butyl esters, the meadowfoam derivative showed a significantly smaller wear scar than that shown by the di-n-butyl derivative of Unidyme® 14.     

Characterization of monomers produced from thermal high-pressure conversion of meadowfoam and oleic acids into estolides

The monomers produced from thermal high-pressure conversion of meadowfoam or oleic acids into estolides were characterized as a complex mixture of fatty acids. Mild reaction conditions produced little change in the starting acids. However, vigorous reaction conditions,e.g. ≥3 h at 250°C with stirring, significantly altered the starting fatty acids.Cis/trans isomerization occurred readily, with the proportion oftrans isomers reaching 57%. In addition, the double bonds migrated throughout all positions of the hydrocarbon chain with concentrations diminishing outward from the starting double bond position. Branching was also observed to a small extent under these conditions and was even more pronounced in the absence of water. Lactones were also identified in the reaction mixture, with contents near 16% in the meadowfoam series. All products can be explainedvia carbocation rearrangement mechanisms that result from protonation of the starting olefins.     

Chemical survey and erucic acid content of commercial varieties of nasturtium,Tropaeolum majus L.

Nasturtium (Tropaeolum majus L.) oil contains the highest levels of erucic acid of known seed oils (75–80%). A significant portion of the acid is attached to the 2-position of the glycerol, and trierucin is a major component (ca. 50%) of the oil. Seeds from eleven varieties of commercially available garden nasturtium (T. majus) were screened for oil content, erucic acid levels and fatty acid distribution. Oil contents ranged fromca. 6 to 11%, and erucic acid levels in the oils ranged from 62 to 80%. One sample ofT. speciosum was also analyzed, and contained 28% oil, fatty acids from C₁₆ to C₂₈ and triglycerides up to C₇₂.     

Positional specificity of γ-ketol formation from linoleic acid hydroperoxides by a corn germ enzyme

We have shown unequivocally that the positional specificity of γ-ketol formation by a corn germ enzyme was different from that observed previously by others with an alfalfa seedling enzyme. When the pure positional isomers of linoleic acid hydroperoxide served as substrates, the corn germ enzyme formed one of two γ-ketols: 12-oxo-9-hydroxy-trans-10-octadecenoic acid from 13-hydroperoxy-cis-9,trans-11-octadecadienoic acid (99+% pure) and 10-oxo-13-hydroxy-trans-11-octadecenoic acid from 9-hydroperoxy-trans-10,cis-12-octadecadienoic acid (96% pure). Also isolated from these reactions was one of two α-ketols commonly found as a result of catalysis by linoleic acid hydroperoxide isomerase: 12-oxo-13-hydroxy-cis-9-octadecenoic acid from the 13-hydroperoxide and 10-oxo-9-hydroxy-cis-12-octadecenoic acid from the 9-hydroperoxide. Evidence is offered that γ-ketol formation is catalyzed by linoleic acid hydroperoxide isomerase, the same enzyme responsible for α-ketol production. Presented at the AOCS Spring Meeting, Dallas, Texas, April, 1975.