Biomedical subjects

Rebecca J Robbins

Publications and source records attributed to Rebecca J Robbins.

6 recordsLinked to original sources

PubMed2006

High-performance liquid chromatography separation and purification of cacao (Theobroma cacao L.) procyanidins according to degree of polymerization using a diol stationary phase.

A new chromatographic approach for separating cacao procyanidins according to their degree of polymerization has been developed. It utilizes diol stationary phase columns operating in normal phase mode with a binary gradient of acidified acetonitrile and methanol-water. Performance of the diol stationary phase was evaluated on an analytical scale utilizing classical chromatographic conditions for the normal phase separation of procyanidins according to their degree of polymerization. The new separation approach was developed on an analytical scale but further extended to the preparative scale. These newly developed analytical and preparative high-performance liquid chromatography procedures were successfully applied to the separation, as well as isolation, of cacao procyanidins from unfermented cacao seeds. The degree of polymerization associated with each molecular weight fraction was determined by mass spectrometry.

Cacao↗

PubMed2006

Analysis of flavanols in foods: what methods are required to enable meaningful health recommendations?

Flavanols and their related oligomeric compounds, the procyanidins, have received increased attention during the past decade due to their reported health benefits. On the basis of compelling data published during the past decade demonstrating that the consumption of certain flavanol-rich foods can improve markers of cardiovascular health, additional clinical, and epidemiological research is clearly warranted to establish appropriate public health recommendations. However, recommendations on the consumption of these foods appropriate for use by health professionals can only be made on the basis of clinical investigations that accurately identify and quantify--through proper analytical measurement systems--the flavanols in the foods used in these investigations. This manuscript provides an overview of the strengths, weaknesses, and limitations of commonly used analytical methods to characterize the content of flavanols in foods. Two nonspecific measurements widely used by investigators, the Folin-Ciocalteu assay and the Oxygen Radical Absorbance Capacity (ORAC) measurement, are discussed in this context, as is the use of various high-performance liquid chromatography methods that provide more specific data related to the content of flavanols in foods. A comparison of the data obtained from these analytical methods to those of the more rigorous high-performance liquid chromatography analyses demonstrates that these nonspecific methods are ill-suited for providing unequivocal data necessary to evaluate the importance of dietary flavanols in the context of improving cardiovascular health. Meaningful dietary recommendations for the consumption of flavanol-rich foods will only be made possible by additional well-designed clinical and epidemiological studies enabled by detailed compositional data obtained through use of appropriate analytical methods.

Biflavonoids↗

PubMed2005

Cultivation conditions and selenium fertilization alter the phenolic profile, glucosinolate, and sulforaphane content of broccoli.

Broccoli is a food often consumed for its potential health-promoting properties. The health benefits of broccoli are partly associated with secondary plant compounds that have bioactivity; glucosinolates and phenolic acids are two of the most abundant and important in broccoli. In an effort to determine how variety, stress, and production conditions affect the production of these bioactive components broccoli was grown in the greenhouse with and without selenium (Se) fertilization, and in the field under conventional or organic farming procedures and with or without water stress. High-performance liquid chromatography/mass spectrometry was used to separate and identify 12 primary phenolic compounds. Variety had a major effect: There was a preponderance of flavonoids in the Majestic variety, but hydroxycinnamic esters were relatively more abundant in the Legacy variety. Organic farming and water stress decreased the overall production of phenolics. Se fertilization increased glucosinolates in general, and sulforaphane in particular, up to a point; above that Se fertilization decreased glucosinolate production. Organic farming and water stress also decreased glucosinolate production. These data show environmental and genetic variation in phenolics and glucosinolates in broccoli, and warn that not all broccoli may contain all health-promoting bioactive components. They further show that selection for one bioactive component (Se) may decrease the content of other bioactive components such as phenolics and glucosinolates.

Agriculture↗

PubMed2005

Selenium enrichment of broccoli: interactions between selenium and secondary plant compounds.

Multiple components of broccoli, such as sulforaphane (Sf) and phenolic acids, may inhibit cancer. Additionally, broccoli can accumulate selenium (Se), and Se has been demonstrated to reduce the risk of cancer. Studies were conducted to determine whether enhancement of broccoli with Se would produce a plant with superior health benefits. Although increasing the concentration of Se in broccoli from <1.0 to >800 microg/g resulted in inhibition of colon cancer in rats, it also decreased the Sf content by >80% and inhibited production of most phenolic acids. The inclusion of Se-enriched broccoli in the diet of rats induced the activity of the selenoprotein thioredoxin reductase beyond the maximum activity induced by Se alone. These results emphasize the complex interactions of bioactive chemicals in a food; attempts to maximize one component may affect accumulation of another, and consumption of high amounts of multiple bioactive compounds may result in unexpected metabolic interactions within the body.

Anticarcinogenic Agents↗

PubMed2004

Development of a quantitative high-performance liquid chromatography-photodiode array detection measurement system for phenolic acids.

A quantitative high-performance liquid chromatography-photodiode array detection method separating 16 phenolic acids was achieved. Six columns and several mobile phases were investigated. Resolution was achieved with a high-purity silica Phenomenex Luna C18 column (150 mm x 4.6 mm, 5 microm) and a binary gradient consisting of CH3OH-water (with 0.1% formic acid) and flow rate set at 0.7 ml/min. Acids were detected and quantitation performed at wavelength representing the lowest energy lambda(max) for individual acids. Extraction procedure from wine was optimized and yields ranged from 79 to 87% based on internal standard recovery. To confirm our quantitative results, identical samples were analyzed both in-house and by a collaborating laboratory. Correlation of two data sets generated linear regression equations that approached unity (0.93-0.98) and R2 values ranging from 0.990 to 0.999.

Calibration↗

PubMed2003

Phenolic acids in foods: an overview of analytical methodology.

Phenolic acids are aromatic secondary plant metabolites, widely spread throughout the plant kingdom. Existing analytical methods for phenolic acids originated from interest in their biological roles as secondary metabolites and from their roles in food quality and their organoleptic properties. Recent interest in phenolic acids stems from their potential protective role, through ingestion of fruits and vegetables, against oxidative damage diseases (coronary heart disease, stroke, and cancers). High performance liquid chromatography (HPLC) as well as gas chromatography (GC) are the two separation techniques reviewed. Extraction from plant matrixes and cleavage reactions through hydrolysis (acidic, basic, and enzymatic) are discussed as are the derivatization reagents used in sample preparation for GC. Detection systems discussed include UV-Vis spectroscopy, mass spectrometry, electrochemical, and fluorometric detection. The most common tandem techniques are HPLC/UV and GC/MS, yet LC/MS is becoming more common. The masses and MS fragmentation patterns of phenolic acids are discussed and tabulated as are the UV absorption maxima.

Chromatography↗