Phytosterol fatty acyl esters

Abbreviations nr—not reported TAG—triacylglycerols FFA—free fatty acids St —phytosterol fatty acyl esters St—free phytosterols FPE—phytosterol ferulate esters tocols-tocopherols and tocotrienols GL—glycolipids PL—phospholipids RBD—refined, bleached, and deodorized oil. 

Abbreviations nr, not reported TAG, triacylglycerols FFA, free fatty acids St E, phytosterol fatty acyl esters St, free phytosterols FPE, phytosterol ferulate esters Tocols, tocopherols and tocotrienols GL, glycolipids PL, phospholipids and RBD, refined, bleached and deodorized oil. 

Com germ oil contains two phytosterol lipid classes, free phytosterols and phytosterol fatty acyl esters (Table 10.1). Phytosterols have been recognized as one of the twelve most important classes of phytonutrients (Fahey et al. 1999). Most chemical identification of phytosterols in vegetable oils has been conducted by saponifying (hydrolyzing with base) the oil and measuring the resulting free phytosterols, usually by GLC (Table 10.4). The major phytosterols... 

Figure 1. HPLC-ELSD chromatogram of corn fiber oil. Insert shows the structure of sitostanyl-ferulate, the major ferulate-phytosterol ester in corn fiber oil (Norton, 1995). Abbreviations StE, phytosterol fatty acyl ester TAG, triacylglycerol, a-Toc, a-tocopherol FFA, free fatty acids CE, p-coumarate-phytosterol esters y-Toc, y tocopherol ST, free phytosterols 1,3-D, 1,2-diacylglycerols FE, ferulate-phytosterol esters 1,2-D, 1,2-diacylglycerols.

Cmde com oil contains principally triglycerides and minor nonpolar and polar lipid components such as free fatty acids, phytosterol fatty acyl esters, free phytosterols, phytosterol femlate esters, tocols, tocopherols, tocotrienols glycolipids, phospholipids, pigments, volatile compoimds, waxes etc. (Gimstone, 2011). 

Phytosterols (PS) are plant sterols or stands found in plants. Plant sterols belong to the triterpene family and differ from cholesterol by having a methyl or ethyl group in C24. Plant stanols, on the other hand, are the saturated form of the plant sterols (Fig. 113.1). PS are present in free or conjugated form as fatty-acyl esters, hydroxycinnamate steryl esters, steryl glycosides, or acylated steryl glycosides. The main function of plant sterols/stanols is to stabilize plant membranes and serve as precursors in the synthesis of steroidal saponins, alkaloids, and other steroids [1]. 

Figure 10.1 Examples of structural formulas of phytosterol and sterol conjugates. FS = free sterol alcohol, SE = sterol fatty acid ester, SF = steryl ferulate, SG = steryl glycoside, ASG = acylated steryl glycoside.

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