U.S. Department of Energy Pacific Northwest National

Laboratory

Detection of Sterol, Detection of Sterol, StanolStanol, Lipid and Carbohydrate Components in Corn , Lipid and Carbohydrate Components in Corn Fiber Products. Fiber Products. 1313C NMR and Chromatographic Methods C NMR and Chromatographic Methods

CH3

CH3

H

CH3

CH3

CH2CH3

HO

CH3

β-Sitosterol24β-Ethylcholesterol

24

CH3

CH3

H

CH3

CH3

HO

CH3

CH3

Campestanol24β-Methyl- cholestane-3β-ol

CH3

CH3

H

CH3

CH3

CH2CH3

HO

CH3

StigmastanolDihydro-β-sitosterol24β-Ethyl-5β-cholestan-3β-ol

24CH3

CH3

H

CH3

CH3

HO

CH3

CH3

Campesterol24β-Methyl-5- cholesten-3β-ol

CH3

CH3

H

CH3

CH3

CH2CH3

HO

H

H

CH3

Stigmasterol3β-Hydroxy-24-Ethyl-5,22-cholestadiene

24

24

24

55

33

22 β-Sitosteryl Oleate

CH2CH3

O

O

CH2CH3

O

O

OCH3

HOβ-Sitosteryl Ferulate

CH2CH3

O

O

HOβ-Sitosteryl Coumarate

CH2CH3

O

O

OCH3

O

O

CH3

β-Sitosteryl Ferulate

O

OH

OCH3

HO

Ac2O

O

OH

OCH3

O

CH3

β-Sitosterol, Dicyclohexyl-Carbodiimide

CH2CH3

O

O

OCH3

HO

SelectiveHydrolysisBu4NOH

Pacific Northwest National LaboratoryJames A. Franz, Nicole M. Stair, Danielle S. Muzatko,

Andrew Schmidt, Todd M. Werpy, Rick J. Orth and Mikhail S. Alnajjar

Archer Daniels MidlandAnne R. Rammelsberg, Kyle E. Beery, and Charles A. Abbas

National Corn Growers AssociationNathan Danielson, Rene J. Shunk

Northern SourcesG. David Mendenhall

Introduction. Archer Daniels Midland, PNNL, and the National Corn Growers Association have collaborated in this study to develop the enhanced recovery of components of wet-milled corn fiber. The components include hemicellulose, and high value sterol and stanolneutraceutical components. The study augmented conventional analytical methods for glycerides and saccharides with the development of 13C NMR spectroscopic data allowing the direct detection, in the raw oil, of a suite of free sterols and stanols, together with fatty acid, ferulate, and coumarate derivatives of sterols and stanols. 13C NMR data for the ferulate and coumarate sterol and stanol esters have not been published, and thus were developed in this work. We present new spectroscopic data for the sterol substances and illustrate approaches to analysis of neutraceutical product distributions.

Figure 1. Major Sterol Components of Wet Milled Corn Fiber Oil These components constitute the bulk of fiber associated sterols

Figure 2. The primary ester derivatives of wet milled corn fiber oil are ferulate and fatty acid sterol and stanol esters. Coumarate esters are found to be trace components, at less than 1/7th the ferulate content.

Figure 3. Authentic ferulate and coumarate esters prepared by acetylation, esterification, and selective hydrolysis steps

Figure 5. The 3-carbon of the sterol and stanol ring system and the aromatic carbons of ferulate and coumarate rings are useful diagnostic resonances for quantifying ratios of ester/free sterol and stanol/sterol ratios. The spectrum above illustrates the dominance of ferulate over coumarate esters (ratio > 7:1). Major product groupings are shown above: (i), free fatty acid carboxyl, (ii),glyceride and sterol/stanol fatty ester carboxylate, (iii), olefinicresonances, primarily of linoleic and oleic acid functions, (iv) quaternary triglyceride C-O, (v) outer triglyceride C-O’s, and (vi) alkane carbon of glycerides. The resonances provide direct measure of classes of sterols, stanols, esters, and primary components in corn oil. Fumarate aromatic resonances remain unchanged as the sterol/fatty component is varied. Similarly, all classes of esters give identical chemical shifts for the C3 sterol carbon, within 0.1 ppm. Thus total fumarate, coumarate, content is directly available. The spectrum (region B) shows the absence of tocopherols in the corn fiber extracts ( aliphatic C-O resonance of the C2 carbon at 74.6 ppm).

Finally, fatty acid esters and sterol ferulate making up peak a, region B can be decomposed into fatty ester and ferulate by comparison with the aromatic ferulate resonances. This exercise reveals that fatty esters occur in excess of ferulates by a ratio of 1.5-2:1, in agreement with independent analysis

Figure 7. GC Analysis of Silylated Sterol Derivatives: A,cholesterol(standard), B, Campesterol; C, Campestanol; D, Stigmasterol, E, β-Sitosterol; F, β-Sitostanol. The GC analysis is carried out after saponification and Trimethylsilylation. Peak at 40.54 is brassicasterol.

74.14374.143

74.14974.149

73.91373.913

74.13974.139

74.12674.126

FerulateFerulateEsterEster

73.86173.86174.16274.16274.02874.02872.03072.030StigmasterolStigmasterol

72.04172.041CampesterolCampesterol

73.65773.65771.52471.524SitostanolSitostanol

74.23174.23172.02872.028SitosterolSitosterol

71.3271.32CholestanolCholestanol

73.85873.85873.90873.90871.8171.81CholesterolCholesterol

OleateOleateAcetateAcetateCoumarateCoumarateFree Sterol/Free Sterol/StanolStanol

O

CH3CH3 CH3 CH3

CH3

HO

R1

R2

R3

5

78

R1=R2=R3 = CH3, α-Tocopherol; R1=R3 = CH3, R2= H, β-TocopherolR1=H, R2=R3=CH3, γ-Tocopherol; R1=R2=H, R3=CH3, δ-Tocopherol

6

12

3

4

Figure 4. Tocopherols and tocotrienols provide useful diagnostic peaks in the aromatic region and for the C-2 resonance. Note the absence of tocopherols in the corn fiber oil (Figure 5, below).

Table. 13C Chemical Shifts of C-3 Carbon of Sterols, Stanols, and Esters.

The data show separation of free sterols and stanols, allowing measurement of total alcohols and sterol/stanol ratio. The data show convenient separation of esters and free sterols, allowing the total of all sterol/stanol nuclei to be measured, and the ratio ester/free sterol to be measured

Figure 6. Figure (left) illustrates saponificationof ferulate and fatty acid esters to free sterols and stanols. Total free sterol and sterol/stanol ratio determined.

0

0.5

1

1.5

2

2.5

3

Campe

sterol

Sitoste

rol

Stigmas

terol

Campe

stano

l

Sitosta

nol

Total

Wt%

Dry

Fib

er

Figure 8 . GC analysis reveals 2.5 wt% sterols and stanols, and a sterol/stanol ratio of 1.6. The relative yields of sterols and stanolsare essentially constant for the corn fiber extract oil for a given hydrolysis condition. NMR analysis reveals 2.6% yield for this material and a sterol/stanol ratio of 1.5.

Summary. With the availability of authentic sterol ester derivatives, this study provides data supporting the direct analysis of sterol/stanol content in grain oils. The spectroscopic methods are particularly useful for components that are difficult to analyze by gas chromatographic methods, or for which inadequate selectivity and structural uniqueness exists for liquid chromatographic methods. The superior structural information available from 13C NMR spectroscopy together with detailed chemical shift information for constituents allows NMR to be conveniently used for analysis of minor organic components in grain byproduct streams.

Acknowledgement. This work was supported by the U.S. Department of Energy, Office of Energy Efficiency, Office of Transportation Technology, Contract DE-FC36-00G10596, A000