Vernonia volkameriaefolia Seed oil: a rich source of epoxy acid

The seeds ofVernonia volkameriaefolia contain 20% oil and are a good source of epoxidized triglycerides. The vernolic acid (cis-12, 13-epoxy-cis-9, 10-octadecenoic acid) content of the oil was 63.5%. The structure of this compound was established by chemical and physical methods, including a study of the mass spectral fragmentation of the parent compound and its derivatives.     

Naturally occurring epoxy oils1

Fatty acids containing oxirane functional groups have unexpectedly been found in wide distribution in seed oils, usually present as longchain glycerides. Four such acids have been discovered:cis- andtrans-9,10-epoxystearic acid; vernolic (cis-12,13-epoxyoleic) acid; coronaric acid, isomeric with vernolic acid but with the oxirane and double-bond functions in the reverse positions; andcis-15,16-epoxylinoleic acid. No single analytical tool has been universally successful in measuring the oxirance content of epoxides. This appears to be caused by the way in which the chemical reactivity of the three-membered cyclic ether is modified by molecular structure and by the presence of nearby substituents. A survey of the published methods for the determination of oxirane functions, including mention of the nature of interfering substances, is given. Techniques used to overcome some of these difficulties are discussed. These procedures include the use of chromatographic and spectrophotometric procedures to solve some of the analytical problems which are encountered. Special consideration is given to vernolic acid and its glycerides since this is the most widely distributed and abundant epoxy acid found in seed oils to date. Presented at the AOCS Meeting, Symposium on Composition and Analysis, New Orleans, May 1967. E. Utiliz. Res. Dev. Div., ARS, USDA.     

Enzymatic synthesis and spectroscopic characterization of 1,3-divernoloyl glycerol fromVernonia galamensis seed oil

cis-12,13-Epoxy-cis-octadecenoic (vernolic) acid occurs in triglycerides of the seed oil ofVernonia galamensis. The seeds also contain a lipase capable of hydrolyzing the triglycerides. Previous investigators incubated the seed ofVernonia anthelmintica and isolated 5.6% yield of 1,3-divernoloyl glycerol. We used crude lipase extract fromV. galamensis seed to synthesize 1,3-divernoloyl glycerol from vernonia oil in pentane at 40% yield. A 94% conversion of the 1,3-divernoloyl glycerol to pure vernolic acid (5.34% oxirane = 98.9% purity) was achieved by a low-energy saponification process. The carbon-13 nuclear magnetic resonance (NMR) spectrum of the 1,3-divernoloyl glyceride indicates a potential for using carbon-13 NMR spectroscopy in the identification of isomeric diglycerides. Thus the paper describes the synthesis, spectroscopic and chemical characterization of 1,3-divernoloyl glycerol, in addition to providing quantitative carbon-13 NMR studies ofV. galamensis oil.     

The stereochemistry of enzymic hydration and of chemical cleavage of D-(+)-cis-12,13-epoxyoleic acid (Vernolic acid)

The absolute optical configurations of (+)-threo-12,13-dihydroxyoleic acid, derived by enzymic hydration of endogenous vernolic acid in crushedVernonia anthelmintica seed, and of (−)-threo-12,13-dihydroxyoleic acid, derived by acetolysis-hydrolysis of vernolic acid, have been determined. The absolute configuration of the (+)-enantiomer is L-12,D-13-dihydroxyoleic acid and, as the parent vernolic acid is known to be D-12,D-13-epoxyoleic acid, the stereochemistry of the enzymic hydration is thus shown to involve attack by hydroxyl at the 12 position with inversion at that position. Chemical cleavage of vernolic acid, on the other hand, involves preferential nucleophilic attack, with inversion, at the 13 position.     

Naturally occurring epoxy acids. IV. The absolute optical configuration of vernolic acid

Vernolic acid [(+)-cis-12,13-epoxyleic acid] was transformed by stereospecific reactions to a mixture ofthreo-9,10,12-andthreo-9,10,13-trihydroxyoctadecanols. The four components of this mixture were separately isolated by chromatography on thin layers impregnated with glycol-complexing agents. The 9,10,12-trihydroxyoctadecanols so obtained were identical to the corresponding derivatives of D-(+)-ricinoleic acid, thereby proving the absolute optical configuration of the epoxy group of vernolic acid to be D. As a corollary to this the absolute configurations of some other oxygenated fatty acids have been deduced.     

Centratherun ritchiei Seed Oil — Characterization of Vernolic Acid

Vernolic acid has been found at the 30.1% level in Centratherum ritchiei (Compositae) seed oil. This acid, cis-12, 13-epoxyoctadec-cis-9-enoic, was isolated by preparative TLC and characterized by IR, NMR and MS. A successful attempt has been made to identify vernolic acid, without its derivatization, by mass spectral study. A reference vernolic acid (Vernonia anthelmintica seed oil) has been used for comparison purpose throughout the study.     

Vernonia anthelmintica (L) willd. highly purified epoxy components from the seed oil

The chief component ofVernonia anthelmintica (L.) A Willd. (ironweed) seed oil, trivernolin, and its minor components, 1,3-divernolin and vernolic (epoxyoleic) acid, have been produced in pound quantities of commercial grade quality (93-99% pure). Refinement of these epoxy components to chromatographically pure compounds has now been accomplished. Trivernolin has been the most difficult, vernolic acid the easiest, to purify. To upgrade trivernolin to about 100% purity, a combination of procedures was necessary including extraction, low temperature crystallizations, adsorbent treatments, and column chromatog-raphy, each monitored by thin-layer chromatog-raphy (TLC). Vernolic acid of 93.7% purity was highly refined by a single pass through a silicic acid column. Some physical characteristics of these epoxy compounds are given. None of the compounds were completely stable in storage as evaluated by Chromatographic procedures.     

Vernonia galamensis: A rich source of epoxy acid

A percolation extraction ofVernonia galamensis seed, affording 38.6% of crude vernonia oil is described. The dark colored crude oil was degummed with water, treated with activated charcoal and bleached with a neutral agent, to give a light colored oil (Lovibond: 0.9 red, 3.5 yellow). Gas chromatographic/mass spectrometric analysis of the refined oil indicates a relative fatty acid composition of 79–81% vernolic (cis-12,13-epoxy-cis-9-octadecenoic) acid, 11–12% linoleic acid, 4–6% oleic acid, 2–3% stearic acid, 2–4% palmitic acid, and a trace amount of arachidic acid.     

Determination of vernolic acid content in the oil ofEuphorbia lagascae by gas and supercritical fluid chromatography

Determination of the content of vernolic acid (12,13-epoxy-9c-octadecenoic) in the oil ofEuphorbia lagascae has been performed by gas chromatography of the fatty acid methyl ester derivatives of the triacylglycerols in the oil and by supercritical fluid chromatography (SFC) of the raw oil and the fatty acid derivatives of the oil. The content of vernolic acid was found to be 55 wt%. The three methods were compared, and SFC analysis of the fatty acid derivatives was found to be the most accurate method.     

The seed oil ofBernardia pulchella (Euphorbiaceae) —A rich source of vernolic acid

The fatty acids from the seed oil ofBernardia pulchella (Euphorbiaceae) have been analyzed by gas chromatography (GC) and GC-mass spectrometry (MS) analysis of their methyl esters. Vernolic acid is the main compound (91%), along with other usual fatty acids. In addition to the quantitation by GC analysis,¹H-nuclear magnetic resonance (NMR) signals from the seed oil have been used to estimate the total epoxy fatty acid content. The structure of vernolic acid has been proven by spectroscopic methods (infrared,¹H, and¹³C-NMR) and by GC-MS analysis of the corresponding silylated hydroxy-methoxy derivative. The 4,4-dimethyloxazoline derivatives of the fatty acid mixture have also been examined by GC-MS, and it was shown that this derivazation reaction is not suitable for the structure analysis of vernolic acid.     

Alchornea cordifolia seed oil: A rich source of a new C20 epoxide, (+)cis-14,15-epoxy-cis-11-eicosenoic acid

A C₂₀ homolog of vernolic acid has been found at the 50% level inAlchornea cordifolia, Euphorbiaceae, seed oil. This new acid, (+)cis-14,15-epoxy-cis-11-eicosenoic (alchornoic) acid, was isolated by high-pressure liquid chromotography and characterized by mass spectrometry, nuclear magnetic resonance and infrared spectroscopy, optical rotary dispersion, and ozonolysis-gas-chromotography.     

HBr-Reactive acids ofMalva sylvestris seed oil

Malva sylvestris seed oil contained 5.6% sterculic, 11.0% malvalic, 1.6% vernolic, 15.6% lauric, 6.6% myristic, 26.6% palmitic, 5.6% palmitoleic, a trace of stearic, 23.0% oleic and 4.0% linoleic acids. The co-occurrence of malvalic and sterculic acids was established by gas liquid chromatography (GLC) of the silver nitrate-methanol treated esters usingSterculia foetida esters as the reference standard. Co-occurrence of epoxy acid (vernolic acid) was confirmed withVernonia anthelmintica as the lipid standard.     

<Emphasis Type="Italic">Geranium sanguineum</Emphasis> (Geraniaceae) seed oil: A new source of petroselinic and vernolic acid

The occurrent of petroselinic acid (18∶1Δ6cis) in seed oils was believed to be limited to the Umbelliferae or Apiaceae, and a few other members of the Umbelliflorae. A major occurrence of petroselinic acid outside the Umbelliflorae must therefore be regarded as highly unusual and surprising. The seed oil of Geranium sanguineum, a member of the family Geraniaceae, has now been found to contain petroselinic and vernolic acids as major FA in its seed oil TAG. These unusual FA have not been reported previously as constituents of Geraniaceae seed oils. The structure and composition of the seed oil FA from G. sanguineum were determined by combined use of chromatographic (TLC, capillary GLC) and spectroscopic (IR, GC-MS) techniques. The double-bond position in petroselinic acid was located unambiguously by the characteristic mass fragmentation of its dimethyldisulfide (DMDS) adduct. The epoxy FA was identified as vernolic acid by co-chromatography and by the mass fragments formed during GC-MS of the products of the epoxy ring-opening reaction with BF₃ in methanol.     

Vernonia anthelmintica (L.) Willd. trivernolin, 1,3-divernolin and vernolic (Epoxyoleic) acid from the seed oil

The epoxy fatty acid components isolated from the seed oil ofV. anthelmintica, Indian ironweed, where the seed had been allowed to undergo lipolysis after grinding, were trivernolin, 1,3-divernolin, and vernolic acid. By inactivation of the hydrolytic enzyme system present in the seed, oil containing more than 50% trivernolin may be obtained. This species has potentialities as a replacement crop for those now in surplus; its seed contains 20 to 26% of an oil rich in epoxyoleic (vernolic) acid combined as glycerides amounting to 70 to 75%. Presented at the A.O.C.S. meeting in St. Louis, 1961. Eastern Utilization Research and Development Division, Agricultural Research Service, U.S.D.A.     

Identification and distribution of epoxyacyl groups in new,natural epoxy oils

New high-epoxy vegetable oils from nine species representing three plant families and four genera have been investigated. The epoxyacyl moiety in at least one oil from each genus was characterized and shown to be the (+)-vernoloyl (cis-12,13-epoxy-cis-9-octadecenoyl) group. Intraglyceride distribution studies revealed a general preference of the (+)-vernoloyl groups for the β-position of triglyceride molecules. Interglyceride distribution of (+)-vernoloyl groups was studied in three oils and found not to agree with predictions based on either 1,2,3-random or 1,3-random-2-random distribution. A striking exception to the general intraglyceride distribution pattern was discovered in the monoepoxy triglyceride fraction fromEuphorbia lagascae seed oil. Presented in part at the AOCS Meeting in Houston, April, 1965. No. Utiliz, Res. Dev. Div., ARS, USDA.     

Search for new industrial oils. XII. Fifty-eight euphorbiaceae oils,including one rich in vernolic acid

Seed oil ofEuphorbia lagascae Spreng. contains 57% ofcis-12,13-epoxy-cis-9-octadecenoic (vernolic) acid. The amt of trivernolin in the glycerides of this species indicates random or restricted random distribution of the vernolic acid. Seed from 57 additional species in the Euphorbiaceae were analyzed for oil and protein contents and also for fatty acid composition of the oils. Iodine values (I.V.) of the oils ranged from 87–221. Among these oils, samples were encountered with as much as 76% linolenic, 77% linoleic or 84% oleic acid. Presented at the AOCS in New Orleans, 1964. A laboratory of the No. Utiliz. Res. & Dev. Div., ARS, USDA. ARS, USDA.     

Compositional variation in seed oils of theCrepis genus

Seed oils from eight species of the genusCrepis (family Compositae) fall into three groups differing in chemical composition. Besides conventional fatty acids the oils contain either vernolic acid (47–68%), crepenynic (36–65%), or both (18–35% vernolic and 7–11% crepenynic). Within any one section of the genus, the oils are chemically similar, among the limited groups of samples examined. No. Utiliz. Res. Dev. Div., ARS, USDA. Crops Research Division, ARS, USDA.     

Hibiscus mutabilis Seed Oil – Characterization of HBr-Reactive Acids

The seed oil of Hibiscus mutabilis (Chameleon rose) (Malvaceae) contains three HBr-reactive fatty acids. These are found to be cis-12, 13-epoxyoleic (vernolic) acid, 5.9%; 9,10-methylene-octadec-9-enoic (sterculic) acid. 7.3%; as well as 8,9-methylene-heptadec-8-enoic (malvalic) acid, 14.0%. Co-occurrence of these acids was established by combined spectroscopie, chromatographic and chemical techniques.     

Note: Thermally removable epoxy adhesives incorporating thermally reversible diels-alder adducts

Thermally reversible adhesives are prepared through the reaction of aliphatic diamines and a diepoxy compound containing two Diels-Alder adducts. The diepoxy compound is formed via the Diels-Alder reaction between two epoxy-containing furans and a bismaleimide. The adhesive displays a T g of m 40°C and a constant shear modulus up to approximately 90°C. At temperatures exceeding 90°C the retro Diels-Alder reaction occurs, which leads to a significant loss in modulus. The loss of modulus is reversible with temperature. A thermally reversible adhesive is proposed based upon the loss of modulus at an elevated temperature, i.e., adhesives bonds are easily broken at elevated temperature where the modulus is low.     

Co-occurrence of Coronaric and Vernolic Acids in Compositae Seed Oils

Seed oils of Lactuca scariola Linn., L. sativa Linn. and Siegesbeckia orientalis Linn., were found to contain epoxy acids in 10.0% (6.0% coronaric + 4.0% vernolic), 27.4% (16.9% coronaric + 10.5% vernolic) and 20.0% (16% coronaric + 4.0% vernolic) amount, respectively, alongwith normal fatty acids. The co-occurrence of the two epoxy acids was confirmed by chromatographic (TLC, GLC), spectroscopic and chemical methods. Further, this was confirmed by mass spectral study of methyl ester and its methoxy hydroxy derivative in the case of S. orientalis seed oil.The seed oils of Chrysanthemum coronariumand Vernonia anthelmintica were used as reference standard.