Structure and occurrence of unusual fatty acids in minor seed oils

In various biological systems, 1,2-epoxides are able to cause biological effects with genetic mechanisms: point mutations, deletions, chromosomal aberrations, gene conversion, crossing-over, cancer and virus (prophage) induction. Dose—response curves are linear, or should be interpreted to have a linear component that predominates at low doses or concentrations. In forward mutation systems the effectiveness is related to the dose in the target cells and to the chemical reactivity. By applying experimentally determined correction factors for difunctionality (in the case of diepoxides or monoepoxides with a reactive substituent such as a carbonyl group), genetic risks may be estimated by a unitary approach, valid for epoxides in general, if not for all alkylating agents. The use of this approach, to calculate type-II errors in negative carcinogenicity tests, indicates that no data presently available support a conclusion that certain epoxides are non-mutagenic or non-carcinogenic, i.e. are less effective than expected from reactivity data. Determination of the rad-equivalence of genetic risks, i.e. the use of corresponding risks from a unit dose of ionizing radiation as a standard, indicates that the risks associated with Threshold Limit Values for epoxides in work environments in Western countries are 1–2 orders of magnitude higher than permissible risks for radiological workers.

Genetic toxicity of some important epoxides

Occurrence and Characteristics of Oils and Fats

Biosynthesis and Function of Polyacetylenes and Allied Natural Products

Publisher Summary The polymers are embedded in or associated with a complex mixture of relatively nonpolar lipids that are collectively called wax because of the similarity of their physical properties to those of the honeycomb material. In most plants, wax can be found on the surface and the crystalline structure of this wax is a rather unique characteristic of each species. The most widespread site of occurrence of wax is the cuticle, and the abundance of production of cuticular waxes by some aerial parts of plants allows easy removal of the most familiar and widely utilized plant waxes such as carnauba wax. Internal organs usually contain little wax, except in rare plants such as jojoba in which large amounts of wax esters are stored as the major energy reserve. This chapter presents a methodology that is useful for examining waxes and polymerized lipids. It discusses the types of compounds found in plant waxes and in lipid-derived polymers and explains their biosynthesis, degradation, and possible functions.

Cutin, suberin, and waxes

A New Type of Naturally Occurring Polyunsaturated Fatty Acid

Thalictrum polycarpum Fatty Acids—A New Class of Fatty Acids from Vegetable Seed Oils*

Chemical analysis of a number of sunflower (Helianthus annuus) seed oil samples revealed a low and variable percentage of hydrogen bromide-reactive material. To characterize the compounds responsible for this reactivity, oil was extracted from selected introductions from Uruguay, Turkey, and Yugoslavia that had been subjected to prolonged storage. Two epoxy fatty acids and two conjugated dienolic acids were isolated from the methyl esters derived from these sunflower seed oils by using a combination of column chromatography and countercurrent distribution. The epoxy acids arecis-9,10-epoxystearic acid (0.5%) andcis-9,10-epoxy-cis-12-octadecenoic (coronaric) acid (2.2%). Characterization of the dienols revealed that they are 9-hydroxy-trans-10,cis-12-octadecadienoic acid (1.2%) and 13-hydroxy-cis-9,trans-11-octadecadienoic acid (1.3%). Fresher seed of some of these introductions contained less of the oxygenated components.

Oxygenated fatty acids of oil from sunflower seeds after prolonged storage.

1. Lamium purpureum L. (Labiatae) seed oil contains 16% of a new acid characterized as (−)-octadeca-5,6-trans-16-trienoic acid (proposed trivial name `lamenallenic acid') (Ia). The acid was isolated as its methyl ester by countercurrent distribution by using a combination of recycle–single withdrawal techniques. Methyl lamenallenate (Ib) is strongly laevorotatory. 2. The structure was established by infrared spectroscopy, nuclear-magnetic-resonance spectroscopy, quantitative hydrogenation and oxidative cleavage data of the original acid and of hydrazine partial reduction products. 3. Other unsaturated esters identified by their cleavage products were oleate, linoleate and linolenate. 4. A very small amount (less than 1%) of methyl laballenate [(−)-methyl octadeca-5,6-dienoate] was also isolated and identified.

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K. L. Mikolajczak

Papers

A New Type of Naturally Occurring Polyunsaturated Fatty Acid

Thalictrum polycarpum Fatty Acids—A New Class of Fatty Acids from Vegetable Seed Oils*

Oxygenated fatty acids of oil from sunflower seeds after prolonged storage.

An octadecatrienoic acid from Lamium purpureum L. seed oil containing 5,6-allenic and trans-16-olefinic unsaturation.

Structure and reactions of a cyanogenetic lipid from Cordia verbenacea DC. seed oil