Purification and identification of components of gamma-oryzanol in rice bran Oil

Comparison of three spectrophotometric methods for the determination of gamma-oryzanol in rice bran oil

A comparison of the results obtained by applying three spectrophotometric methods (at fixed wavelength, second-derivative and multicomponent analysis) to the determination of gamma-oryzanol in rice bran oil is reported. At fixed wavelength the results are more accurate when using isopropyl alcohol, rather than n-heptane, to dilute the oil samples, because the absorption bands of gamma-oryzanol are red-shifted and the absorbance, measured at lambda(max)=327 nm, is less affected by the interference of the oil "matrix" (lambda(max)=314 nm in n-heptane).However, to obtain accurate results also in oils with a low content of gamma-oryzanol, it is necessary to perform the analysis using second-derivative ((2)D330.365) or multicomponent (lambda=310-360 nm) methods. The first one fully removes the interference of oil matrix whilst the second, which needs a specific computational program to process the spectrophotometric data, furnishes evidence the presence of some unexpected interference in the analysis and/or standards which are not representative of the analysed samples, from the square root of the sum of the squared differences at each point between the linear combination of the standards and the unknown spectra (RMS error).Finally, some aspects of the chemical, spectroscopic (UV, IR) and thermoanalytical (TG, DSC) behaviour of gamma-oryzanol and the values of the parameters which enable "computation" of its UV spectra are reported.

Coupled liquid chromatography-gas chromatography for the rapid analysis of gamma-oryzanol in rice lipids

An approach based on on-line coupled liquid chromatography-gas chromatography (LC-GC) was developed for the rapid analysis of gamma-oryzanol in rice. Total lipids were extracted from rice and subjected to LC-GC without any prior purification. gamma-Oryzanol was pre-separated by HPLC from rice lipids and transferred on-line to GC analysis in order to separate its major constituents. 24-methylenecycloartanyl ferulate, cycloartenyl ferulate, campesteryl ferulate, beta-sitosteryl ferulate and campestanyl ferulate. The identities of the compounds were confirmed by off-line GC-MS analysis. Total gamma-oryzanol content could be quantified by HPLC-UV detection and the distribution of gamma-oryzanol constituents could be determined by on-line coupled GC analysis. The proposed methodology paves the way for high-throughput investigations providing information on natural variations in gamma-oryzanol content and its composition in different rice varieties.

Phytosterols, phytostanols, and their conjugates in foods: structural diversity, quantitative analysis, and health-promoting uses

Phytosterols (plant sterols) are triterpenes that are important structural components of plant membranes, and free phytosterols serve to stabilize phospholipid bilayers in plant cell membranes just as cholesterol does in animal cell membranes. Most phytosterols contain 28 or 29 carbons and one or two carbon-carbon double bonds, typically one in the sterol nucleus and sometimes a second in the alkyl side chain. Phytostanols are a fully-saturated subgroup of phytosterols (contain no double bonds). Phytostanols occur in trace levels in many plant species and they occur in high levels in tissues of only in a few cereal species. Phytosterols can be converted to phytostanols by chemical hydrogenation. More than 200 different types of phytosterols have been reported in plant species. In addition to the free form, phytosterols occur as four types of "conjugates," in which the 3beta-OH group is esterified to a fatty acid or a hydroxycinnamic acid, or glycosylated with a hexose (usually glucose) or a 6-fatty-acyl hexose. The most popular methods for phytosterol analysis involve hydrolysis of the esters (and sometimes the glycosides) and capillary GLC of the total phytosterols, either in the free form or as TMS or acetylated derivatives. Several alternative methods have been reported for analysis of free phytosterols and intact phytosteryl conjugates. Phytosterols and phytostanols have received much attention in the last five years because of their cholesterol-lowering properties. Early phytosterol-enriched products contained free phytosterols and relatively large dosages were required to significantly lower serum cholesterol. In the last several years two spreads, one containing phytostanyl fatty-acid esters and the other phytosteryl fatty-acid esters, have been commercialized and were shown to significantly lower serum cholesterol at dosages of 1-3 g per day. The popularity of these products has caused the medical and biochemical community to focus much attention on phytosterols and consequently research activity on phytosterols has increased dramatically.

Screening of chemiluminescence constituents of cereals and DPPH radical scavenging activity of gamma-oryzanol

The chemiluminescence (CL) constituents of cereals were detected by CL using the H(2)O(2)-acetaldehyde system. The cereals tested, such as rice, millet and sorghum, exhibited various levels of CL activity. The gamma-oryzanol fraction was extracted from brown rice and separated into four constituents by HPLC. The four constituents were identified as cycloartenyl ferulate, 24-methylenecycroartanyl ferulate, campesteryl ferulate and beta-sitosteryl ferulate. Free radical scavenging activities with 1,1-diphenyl-2-picrylhydrazyl (DPPH) and CL intensities of four constituents (gamma-oryzanol components) were measured and compared with that of gallic acid, which is a typical free radical scavenger. Four constituents scavenged DPPH radicals and scavenging activities were proportional to CL intensities. Concentrations of four CL constituents required to quench 50% (IC(50)) of the free radicals ranged from 0.9 to 1.1 mmol/L. We demonstrated that measurement of CL intensities was a rapid and convenient method for screening DPPH radical scavenging activities of rice.

Identification of a sucrose diester of a substituted beta-truxinic acid in oats

A novel compound, 4,4'-dihydroxy-3,3'-dimethoxy-beta-truxinic acid esterified to sucrose through the fructosyl 3-and 6-carbons (1), was isolated from oat grains (Avena sativa L.). Its structure was determined by a combination of mass spectrometry and 1-D and 2-D NMR. The amounts of 1 in groats of six different oat cultivars ranged from 101 to 150 microg g(-1) (dry wt). None was detected in the hulls. The free diacid, 4,4'-dihydroxy-3,3'-dimethoxy-beta-truxinic acid (2), could not be detected in groats nor in hulls.

Influence of high-oryzanol rice bran oil on the oxidative stability of whole milk powder

The effect of high oryzanol rice bran oil (RBO) on the oxidative stability of low-heat and high-heat whole milk powder (WMP) was investigated. Milk (3.6% fat) was fortified with RBO at 0.1 and 0.2% (wt/wt) and was concentrated and dried. Control WMP was made without RBO addition. Thiobarbituric acid reactive substances (TBARS) were used to monitor oxidation during storage at 45 degrees C for 40 d. The oxidation of low-heat WMP was significantly reduced by addition of 0.1% RBO, but there was no significant effect on the oxidation of high-heat WMP. An increase of RBO to 0.2% did not significantly improve the oxidative stability when compared with 0.1% RBO. The TBARS in RBO-fortified, low-heat WMP increased with storage time up to 30 d but decreased with further storage to 40 d. The TBARS in all high-heat WMP and low-heat control WMP increased up to 20 d storage and then decreased with further storage. The most likely reason for this increase was due to the reaction of TBARS with milk proteins. Addition of RBO reduced the L (lightness) value and increased the b (yellowness) value but had no effect on the a (redness) value. When compared with the control milk powder, consumers could not detect any effect on the flavor of the reconstituted 0.1% RBO WMP but could detect a flavor difference in the 0.2% RBO WMP.