Sterculic oil

Researchers have used one of two approaches to quantify endogenous synthesis. The first involves inhibiting the A-9-desaturase, thereby inhibiting conversion of VA to RA. Using abomasal infusion of sterculic oil to inhibit A-9-desaturase activity, combined with monoene/saturate pair ratios to correct for the extent of inhibition, Griinari et al. (2000) estimated that a minimum of 64% of RA in their milk fat samples was derived from desaturation of VA. Further experiments using sterculic oil also indicated that the... 

Double bonds are accommodated by rings of all sizes The smallest cycloalkene cyclo propene was first synthesized m 1922 A cyclopropene nng is present m sterculic acid a substance derived from one of the components of the oil present m the seeds of a tree (Sterculia foelida) that grows m the Philippines and Indonesia... 

Sterculic acid is a potent inhibitor of several desaturases, which are the enzymes responsible for the formation of double bonds in long-chain acids used as fuels, membrane components, and other critical biological molecules. Consequently, vegetable oils containing sterculic acid must be hydrogenated or processed at high temperatures to reduce or destroy the cyclopropene ring. 

Many chemists once believed that a cyclopropene could never be made because it would snap open (or polymerize) immediately from the large ring strain. Cyclopropene was eventually synthesized, however, and it can be stored in the cold. Cyclopropenes were still considered to be strange, highly unusual compounds. Natural-product chemists were surprised when they found that the kernel oil of Sterculia foelida, a tropical tree, contains sterculic acid, a carboxylic acid with a cyclopropene ring. 

Halphen Test for Detecting Cottonseed Oil (Cb 1-25) estimates the presence of cottonseed oil in vegetable or animal fats or oils as the result of a pink color formed between the reagent and cyclopropenoic fatty acids (sterculic and malvalic) normally present in cottonseed oil. 

Glanded cottonseed kernels contain 1.1-1.3% gossypol (19) plus related pigments that affect nutritional properties and color of the oil and meal. Cottonseed also contains the cydoptopenoid acids, malvahc and sterculic acids, which exist as glycerides and are concentrated in the seed axis (32). 

This type of fatty acid is usually found at low levels (around 1%) in plant oils that contain cyclopropene acids. Cyclopropene acids are characteristic for oils from the Malvalaceae, Stercu-liaceae, Bombaceae, Tiliaceae, and Sapicidaceae families with sterculic acid (9,10-methyleneoctadec-9-enoic acid) and mal-valic acid (8,9-methyleneheptadec-8-enoic acid) as two major compounds. Sterculic acid is more abundant (about 50% of the total fatty acids in Sterculiafoetida oil). 2-Hydroxysterculic acid may also be present in this oil as a possible intermediate in the biosynthesis of malvalic acid (through a-oxidation of sterculic acid). 

Jones (36) reviewed the natural antinutrients of cottonseed protein products— gossypol and the cyclopropenoic fatty acids (CPFA malvalic and sterculic acids). The CPFAs participate in forming the pink color complex in the Halphen reaction, a test specific for the admixture of cottonseed oil with other oils and fats. They also inhibit A9 desamrase, an enzyme that converts stearic acid into oleic acid, and thus increase hardness of fats from animals (e.g., pig backfat and lard) raised or finished on feedstuffs containing high levels of polyunsamrated oils like corn. Feed industry practice is to limit cottonseed lipids to no more than 0.1-0.2% in the diet of laying hens to avoid pink discoloration of egg whites and alterations of the vitelline membrane that cause pasty yolks. 

Cottonseed oil contains up to 0.5% of a pair of unique fatty acids malvalic (18 1) and sterculic (19 1). These acids are characterized by the presence of a cyclopropene group at or near the center of the fatty acid chain. Under appropriate conditions these give colored compounds and the development of a red color in the Halphen test (reaction with sulfur in carbon disulfide in the presence of amyl alcohol) is due to the cyclopropene acids and therefore characteristic of cottonseed oil (and other minor oils containing cyclopropene acids). This test for cottonseed oil was developed over a century ago in 1897. Inclusion of cyclopropenoid acids in animal diets causes undesirable physiological effects such as reduced egg production, poor hatching, and pink egg whites in chickens, and in rats, decreased growth and sexual development and... 

One feature distinguishing cottonseed oil from other commercial oils is its content of C20, C22 and C24 saturated fatty acids. The presence of cyclo-propenoid acids (0.1-1.3%) (Bailey etal., 1966 Pan-dey and Suri, 1982) is of even greater importance. These acids are responsible for giving a positive Hal-phen test (Halphen, 1897) which has been used to characterize cottonseed oil for almost 100 years. The major cyclopropenoid acids are sterculic (C19) and malvalic (Cis) (Shenstone and Vickery, 1959, 1961) (Sections 1.8 and 3.2.14). 

This oil contains malvalic (M), dihydromalvalic (MH2), sterculic (S) and dihydrosterculic (SH2)... 

Occurs in a number of seed oils, frequently with sterculic acid, and in some microorganisms. Mp 35.6-36.5 , 38.6-39.0 . 

A popular method is to analyse the total fatty acid methyl esters by CjC after reaction with silver nitrate/anhydrous methanol for 2 h at 30°C (Bianchini, Ralaimanarivo and Gaydou, 1981 Eisele et aL, 1974 Gaydou, Bianchini and Ralaimanarivo, 1983 Ralaimanarivo, Gaydou and Bianchini, 1982). Most fatty esters remain unchanged, but cyclopropene esters are converted to later-eluting methoxy ether derivatives and small amounts of ketone derivatives. Two partially resolved peaks, those from sterculic acid eluting later, are observed for each type of derivative from each cyclopropene acid and can be quantified and used to determine the proportion of sterculic and malvalic acids in the untreated oil. Verification of the identities of the acids can be determined from GC-MS of the methyl esters of the products (Ahmad et al., 1979 Eisele et ai, 1974) but prominent allylic ions in the mass spectra of the DMOX derivatives of the methoxy ethers are more readily interpretable to reveal the positions of the cyclopropene rings (Spitzer, 1995). 

Figure 5.8 Mass spectra (70 eV) of dimethyloxazoline derivatives of A, 9,10-methyleneocta-dec-9-enoic (sterculic) acid B, 2-hydroxy-sterculic acid. Redrawn from Spitzer, V., GC-MS characterization (chemical ionization and electron impact modes) of the methyl esters and oxazoline derivatives of cyclopropenoid fatty acids, J. Am. Oil Chem. Soc., 68(12), 963-9,1991.

Azima tetracantha is a flowering shrub that grows in India with a seed oil content of 12% (Daulatabad et al., 1991). Major fatty acids are linoleic (28.8%), linolenic acid (22%) and oleic acid (15.3%), with smaller amounts of palmitic (5.2%), myristic (4.2%), lauric (3.5%) and stearic (1.6%). This seed contains three unusual fatty acids ricinoleic (9.8%), malvalic (4.0%) and sterculic (5.6%). 

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