Biomedical subjects

Kevin B Hicks

Publications and source records attributed to Kevin B Hicks.

14 recordsLinked to original sources

PubMed2006

Reinvestigation of the effect of heat pretreatment of corn fiber and corn germ on the levels of extractable tocopherols and tocotrienols.

We previously reported that heat pretreatment of corn fiber (150 degrees C, 1 h) caused a tenfold increase in the levels of extractable gamma-tocopherol. The current study was a reinvestigation of the previous effect, using improved methods (HPLC with fluorescence detection, diode-array UV detection, and mass spectrometry) for tocol analysis. Heat pretreatment did not cause an increase in the levels of any of the tocopherols or tocotrienols in corn fiber oil, but lowered the levels of three of the tocols and had no effect on the levels of the other two tocols. Heat pretreatment of corn germ had a similar effect. UV and mass spectra indicated that the peak that we had identified as gamma-tocopherol in our previous report was probably a mixture of oxidation products of triacylglycerols. Thus, heat treatment of corn germ or other corn-oil containing fractions at high temperatures leads to decreases in gamma-tocopherol, gamma-tocotrienol, and delta-tocotrienol and to the production of triacylglycerol oxidation products.

Chromatography, High Pressure Liquid↗

PubMed2006

Corn stover fractions and bioenergy: chemical composition, structure, and response to enzyme pretreatment.

Information is presented on structure, composition, and response to enzymes of corn stover related to barriers for bioconversion to ethanol. Aromatic compounds occurred in most tissue cell walls. Ferulic acid esterase treatment before cellulase treatment significantly improved dry weight loss and release of phenolic acids and sugars in most fractions over cellulase alone. Leaf fractions were considerably higher in dry weight loss and released sugars with esterase treatment, but stem pith cells gave up the most phenolic acids. Results help identify plant fractions more appropriate for coproducts and bioconversion and those more suitable as residues for soil erosion control.

Bioreactors↗

PubMed2005

Biodegradable composites from sugar beet pulp and poly(lactic acid).

Sugar beet pulp and poly(lactic acid) (PLA) composites were prepared by compression-heating. The resultant thermoplastics had a lower density, but they had tensile strength similar to that of pure PLA specimens as well as the same geometric properties. Tensile properties depended on the initial water content of sugar beet pulp and the process by which composites were manufactured. In comparison with sugar beet pulp, the composite showed improved water resistance. This can be attributed to the hydrophobic character of PLA and pulp-matrix interactions. The composite thermoplastics showed suitable properties for potential use as lightweight construction materials.

Beta vulgaris↗

PubMed2005

Encapsulation of essential oils in zein nanospherical particles.

Three essential oils, oregano, red thyme, and cassia (100% pure oil), were encapsulated by phase separation into zein nanospheres. Topographical images indicated that the powders were made up of irregularly shaped particles ( approximately 50 mum) containing close-packed nanospheres. Approximately 31% of the oregano encapsulated particles had mean diameters greater than 100 nm compared to 19% for the zein alone particles. In vitro digestion of zein particles with pepsin at a concentration ratio of 10:1 was complete after 52 h in phosphate-citrate buffer, pH 3.5, at 37 degrees C by spectroscopic analysis. Nonenzymatic, aqueous in vitro release of essential oils from encapsulated zein particles was carried out in phosphate buffered saline at pH 7.4 and 37 degrees C. Release occurred at varying rates over 20 h probably from different locations within the closely packed nanospheres of different sizes. Gel electrophoresis SDS-PAGE of zein incubated with freeze-dried swine manure solids at 37 degrees C indicated that preformed microbial enzymes capable of digesting zein within minutes were present in the manure. Except for differences in size of nanospheres, no structural differences were resolved by several microscopic methods, suggesting that the oil and proteins phases were blended during phase separation.

Animals↗

PubMed2005

Interaction of various pectin formulations with porcine colonic tissues.

Pectins of low and high degrees of esterification, as well as pectin derivatives carrying primary amines, were investigate for gel forming ability with mucosal tissues. The combination of scanning electronic microscopy and small deformation dynamic mechanical studies revealed that pectins with higher net electrical charges are more bioadhesive than the less charged ones. Both the negatively charged pectin formulation, P-25, and the positively charged formulation, P-N, were able to synergize with the mucus to produce rheologically strengthened gels. The highly esterified pectin, P-94, also synergized with the mucosal glycoproteins to form a gel structure via coil entanglements. The ex vivo studies further confirmed the microstructures of mucus gel networks with adsorbed pectins. When incubated with porcine intestinal mucus membrane, P-94 gels were found generally bound to the lumen area, P-25 gels were able to penetrate deeply near the wall area, P-N gels interacted with mucins via electrostatic bonding and dispersed into the whole area from the lumen to the wall. Hence, both P-N and P-94, by enhancing the protective barrier properties of mucus systems, may be useful alternatives for the treatment of mucus related irritation and infection. In drug-delivery systems, P-N and P-25 would deliver incorporated drugs mainly by pectin dissolution, while a diffusion mechanism would release drugs from P-94 gels.

Animals↗

PubMed2004

The in vitro hydrolysis of phytosterol conjugates in food matrices by mammalian digestive enzymes.

All fruits, vegetables, and grains contain phytosterols. Numerous clinical studies have documented that phytosterols lower LDL-cholesterol levels and thereby reduce the risk of cardiovascular disease. Most experts believe that the cholesterol-lowering mechanism of phytosterols requires that they be in their "free" form. In addition to their occurrence in the free form, phytosterols also occur as four common phytosterol conjugates: (i) fatty acyl esters, (ii) hydroxycinnamate esters, (iii) steryl glycosides, and (iv) fatty acylated steryl glycosides. This study was undertaken to investigate the extent of hydrolysis of four common phytosterol conjugates by mammalian digestive enzymes (cholesterol esterase and pancreatin, a mixture of pancreatic enzymes) and for comparison purposes, by KOH. Two types of purified hydroxycinnamate esters (sitostanyl ferulate and oryzanol, a mixture of hydroxycinnamate esters purified from rice bran oil) were hydrolyzed by cholesterol esterase and by pancreatin. Both cholesterol esterase and pancreatin hydrolyzed the phytosteryl esters in two functional food matrices, and they hydrolyzed the hydroxycinnamate esters in corn fiber oil. This is the first report to demonstrate that phytostanyl ferulate esters (which are present at levels of 3-6% in corn fiber oil) are hydrolyzed by pancreatic cholesterol esterase. It is also the first report that pancreatin contains enzymes that hydrolyze the fatty acyl moiety of fatty acylated steryl glycoside, converting it to steryl glycoside. Pancreatin had no effect on steryl glycosides. The ability of pancreatin to hydrolyze three other types of lipid conjugates was also evaluated. Phospholipids were completely hydrolyzed. About half of the galactolipids were hydrolyzed, and less than 10% of the polyamine conjugates were hydrolyzed. The extents of hydrolysis of phytosteryl esters by base (saponification) were also studied, and conditions commonly used for the saponification of acyl lipids (1.5 N methanolic KOH, 30 min at 70 degrees C), were found to result in a nearly 100% hydrolysis of TAG but only about 35-45% hydrolysis of the phytosteryl fatty acyl esters or phytosteryl hydroxycinnamate esters.

Animals↗

PubMed2004

Pearling barley and rye to produce phytosterol-rich fractions.

Because of the positive health effects of phytosterols, phytosterol-enriched foods and foods containing elevated levels of natural phytosterols are being developed. Phytosterol contents in cereals are moderate, whereas their levels in the outer layers of the kernels are higher. The phytosterols in cereals are currently underutilized; thus, there is a need to create or identify processing fractions that are enriched in phytosterols. In this study, pearling of hulless barley and rye was investigated as a potential process to make fractions with higher levels of phytosterols. The grains were pearled with a laboratory-scale pearler to produce pearling fines and pearled grains. Lipids were extracted by accelerated solvent extraction, and nonpolar lipids were analyzed by normal-phase HPLC with ELSD and UV detection. Total sterol analyses were performed by GC. After a 90-s pearling, the amounts of pearling fines from hulless barley and rye were 14.6 and 20.1%, respectively, of the original kernel weights. During pearling, higher levels of phytosterols and other lipids were fractionated into the fines. The contents of free sterols and sterols esterified with FA in the fines were at least double those in the whole grains. Pearling fines of hulless barley and rye contained >2 mg/g phytosterol compounds, which makes them a good source of phytosterols and thus valuable raw materials for health-promoting foods.

Food↗

PubMed2004

Pectin/poly(lactide-co-glycolide) composite matrices for biomedical applications.

The aim of the research was to develop matrices for the delivery of biologically active substances for tissue regeneration. To this end, a new biodegradable matrix composed of a hydrophobic porous poly(lactide-co-glycolide), p(LGA), network entangled with another network of hydrophilic pectin was fabricated in the presence of calcium chloride. The calcium salts function as both a pore forming reagent and cross-linker for the formation of pectin networks; the method combines creating pores and cross-linking polymers in one step. Microscopic imaging and dynamic mechanical analysis revealed a double-network structure of the composite matrices. The pectin enables the composite to carry signal molecules. This is accomplished by linking signal molecules to pectin by physical adsorption or by chemical reaction. The p(LGA) networks in the composite impart mechanical properties comparable to p(LGA) alone. The mechanical properties of the composite are far superior to matrices containing only pectin. Furthermore, the pectin-containing matrices improved cell adhesion and proliferation when compared to plain p(LGA) matrices, as determined in vitro by osteoblast culture.

Adsorption↗

PubMed2004

Fermentation of "Quick Fiber" produced from a modified corn-milling process into ethanol and recovery of corn fiber.

Approximately 9% of the 9.7 billion bushels of corn harvested in the United States was used for fuel ethanol production in 2002, half of which was prepared for fermentation by dry grinding. The University of Illinois has developed a modified dry grind process that allows recovery of the fiber fractions prior to fermentation. We report here on conversion of this fiber (Quick Fiber [QF]) to ethanol. QF was analyzed and found to contain 32%wt glucans and 65%wt total carbohydrates. QF was pretreated with dilute acid and converted into ethanol using either ethanologenic Escherichia coli strain FBR5 or Saccharomyces cerevisiae. For the bacterial fermentation the liquid fraction was fermented, and for the yeast fermentation both liquid and solids were fermented. For the bacterial fermentation, the final ethanol concentration was 30 g/L, a yield of 0.44 g ethanol/g of sugar(s) initially present in the hydrolysate, which is 85% of the theoretical yield. The ethanol yield with yeast was 0.096 gal/bu of processed corn assuming a QF yield of 3.04 lb/bu. The residuals from the fermentations were also evaluated as a source of corn fiber oil, which has value as a nutraceutical. Corn fiber oil yields were 8.28%wt for solids recovered following pretreatment.

Biomass↗

PubMed2003

Evaluation of a commercial enzyme-based serum cholesterol test kit for analysis of phytosterol and phytostanol products.

Plant sterols (phytosterols) have been shown to possess serum cholesterol-lowering properties. In recent years, several phytosterol-enriched functional food products have been developed and marketed. Some phytosterol products contain common unsaturated sterols and some contain a subset of phytosterols called phytostanols (saturated sterols, also called plant stanols). Current methods for the quantitative analysis of plant sterols are labor intensive and require sophisticated gas or liquid chromatographs. In this study, a popular commercial spectrophotometric serum cholesterol test kit was evaluated for the analysis of plant sterols. The results indicate that the method could be modified to analyze phytosterols and phytostanols by increasing the incubation time. Both free phytosterols and fatty acyl phytosteryl esters were quantitatively analyzed, but ferulate phytosteryl esters, such as those that are found in corn and other cereals, were not hydrolyzed by the enzymes in the test kit and therefore were not detected.

Cholesterol↗

PubMed2003

Pectin-based systems for colon-specific drug delivery via oral route.

Pectin-derived matrices are now being examined and tested for controlled drug delivery. Pectin is intact in the upper gastrointestinal tract and degraded by colonic microflora. The composition of this microflora remains relatively consistent across a diverse human population. Thus, pectin-derived drug carriers provide promising potential for colon-specific drug delivery. This paper reviews recent developments in pectin-derived formulations. Subjects reviewed include gelation of pectin, calcium cross-linked pectinate, composites of pectin and other polymers, technologies to fabricate pectin into useful drug delivery vehicles, and methods to evaluate release kinetics of incorporated drugs. This article discusses advantages, limitations, and possible future developments in pectin-based formulations with particular emphasis on the field of colon-specific drug delivery.

Administration, Oral↗

PubMed2002

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.

Animals↗

PubMedDate not supplied

Pectin/zein beads for potential colon-specific drug delivery: synthesis and in vitro evaluation.

Novel complex hydrogel beads were prepared from two edible polymers: pectin, a carbohydrate from citrus fruits, and zein, a protein from corn. The pectin/zein complex hydrogels did not swell in physiological environments, but hydrolyzed in the presence of pectinases. An in vitro study showed the capacity of the hydrogels to endure protease attack and residence time variation. The physical and biological properties of the new hydrogels were attributed to molecular entanglement of the two polymers. The pectin networks were stabilized by the bound zein molecules. In turn, the pectin networks shielded the bound zein from protease digestion.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMedDate not supplied

Pectin gel vehicles for controlled fragrance delivery.

Using citronellal as a model compound, pectin gels formulations were evaluated for the controlled fragrance release by kinetic and static methods. The pectins with higher degrees of esterification induced a stronger molecular association with the nonpolar fragrance. This resulted in a prolonged duration of fragrance release and the limitation of fragrance adsorption to the receptor skin layers. The increase in pectin concentrations suppressed the fragrance release by a diffusion mechanism. Blocking the carboxyl groups of pectin with calcium ions reduces the hydrophilicity of pectin and provides physical barriers for citronellal diffusion. The pectin/calcium microparticles are promising materials for controlled fragrance release.

Acyclic Monoterpenes↗