Steryl ferulates

Norton, R. A. Quantitation of steryl ferulate and p-coumarate esters from corn and rice. Lipids 1995 30(3) 269-274. 

Norton, R.A. (1995) Quantitation of steryl ferulate and p-coumaric esters from com and rice. lipids, 30,... 

Nystrom, L. Makinen, M. Lampi, A. Piironen, V. 2005. Antioxidant activity of steryl ferulate extracts from rye and wheat bran. J. Agric. Food Chem. 53 2503-2510. 

Keywords Plant sterol phytosterol sterol conjugate steryl ferulate gamma-oryzanol steryl glycoside acylated steryl glycoside steryl ester free sterol. 

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.

Steryl ferulates (SFs) are esters of phytosterols and ferulic acid. Also esters of other phenolic acids, namely p-coumaric acid and caffeic acid,... 

Table 10.1 Levels of steryl ferulates in natural sources.

Figure 10.3 Structural formulas of selected steryl ferulates identified in y-oryzanol.

Table 10.2 Antioxidant activities of steryl ferulates in various studies. 

Steryl ferulates evaluated (in the order of inereasing antioxidant aetivity) ... 

Model system (Monitored factor representing oxidation) Substrate Temp, (if not ambient) Steryl ferulates evaluated (in the order of increasing antioxidant activity) Reference... 

Other Biological Functions of Steryl Ferulates/Sterol Conjugates... 

Owing to the UV absorbance of ferulic acid, steryl ferulates (SFs) can be analyzed from oils and total lipid extracts using UV-spectropho-tometric methods. These methods are robust and easy to perform, and provide a good estimate of the total content of SFs in a sample. The absorption maximum varies between different solvents, being 314nm, 327 nm, and 328 nm in heptane, isopropanol, and methanol, respectively (Evershed et ah, 1988 Seetharamaiah and Prabhakar, 1989 Bucci et ah, 2003). Further, the specific extinction coefficients for quantification of SFs are 358.9 cm in hexane (314nm, 25 °C) and 19,500 L mol cm (328 nm) (Evershed et ah, 1988 Seetharamaiah and Prabhakar, 1989). 

The oil matrix, i.e. other components present in the oil samples, may naturally interfere with the analysis and quantification. To overcome this, Bucci et ah (2003) suggested using second derivatives or a multicomponent analysis instead of a fixed wavelength. With these it is possible to improve the accuracy of the method, especially with oils with a relatively low content of steryl ferulates. 

Figure 10.5 UV-spectra of the c -steryl ferulates (upper line) and trans-sieryX ferulates (lower line).

NP-HPLC Normal-phase liquid chromatographic methods applying Diol-columns or common silica columns are well suited for the analysis of the total steryl ferulate content. They require very little sample preparation, as total lipid extracts can frequently be directly injected into the column without purification or fractionation. Run times for SFs are also relatively short, and a good separation from other lipid components can be obtained in less than 10 min in traditional HPLC systems. Depending on the column type and the sample, SFs elute as one or two peaks. Two peaks are obtained from the separation of SFs, which have ferulic acid both in cis- and trans- configuration (Nystrom et ah, 2008). The relative retention time (obtained with a silica column and hexane/ethyl acetate 97 3 as eluent) of the cis- form is about 0.5 smaller than that of steryl irans -ferulates (Akihisa et al., 2000). 

Table 10.3 Columns and eluent systems used for the analysis of steryl ferulates in selected studies. 

Evershed, R.P. Spooner, N. Preseott, M.C. Goad, L.J. 1988. Isolation and Characterization of intact steryl ferulates from seeds. J. Chromatogr. 440 23-35. 

Fang, N. Yu, S. Badger, T.H. 2003. Charaeterization of triterpene aleohol and steryl ferulates in rice bran using LC-MS/MS. J. Agrie. Food Chem. 51 3260-3267. 

Miller, A. Engel, K.H. 2006. Content of y-oryzanol and composition of steryl ferulates in brown rice (Oryza sativa L.) of European origin. J. Agric. Food Chem. 54 8127-8133. 

Nystrom, L. Achrenius, T. Lampi, A.-M. Moreau, R.A. Piironen, V. 2007a. A comparison of the antioxidant properties of steryl ferulates with tocopherol at high temperatures. Food Chem. 101 947-954. 

Nystrom, L. Paasonen, A. Lampi, A.-M. Piironen, V. 2007c. Total plant sterols, steryl ferulates and steryl glycosides in milling fractions of wheat and rye. J. Cereal Sci. 45 106 115. 

Nystrom, L. Moreau, R.A. Lampi, A.-M. Hicks, K.B. Piironen V. 2008. Enzymatic hydrolysis of steryl ferulates and steryl glycosides. Eur. Food Res. Tech. 227 727-733. 

From the perspective of human health, phenylpropanoids such as resveratrol, steryl ferulate, and isoflavones have been implicated in reducing the risk of heart disease and certain cancers. " Recently, it has been suggested that resveratrol may also increase longevity by inducing a signal cascade normally associated with a calorie reduced diet. Finally, phenylpropanoids have been found to play diverse roles in ecology. A host of compounds, including the phenylpropanoid... 

A mixture of free sterols, steryl ferulates, and diglycerides from rice grain were found to induce oviposition of the rice grain weevil, Sitophilus zeamais. When the individual components of the mixture were tested separately, however, they repelled the female from egg laying (Harbome, 1987). 

Ibn steryl ferulate and coumarate esters were extracted from com and rice and were identified using a C g column (A = 325 nm) and an 82/3/2/13 acetonitrile/1-butanol/acetic acid/water mobile phase. Good resolution was obtained and the elution was complete in 35 min. Chromatograms showing the effects of varying water level (1-21%) on peak shape and resolution were shown. Levels from 70 pg to 26mg/g sample were tabulated [1065]. 

Feruhc acid esters of phytosterols (steryl ferulates) have been identified in rice, wheat, rye, triticale and barley. The highest amounts of ferulated phytosterols occur in rice. They are also... 

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