Abstract An efficient reverse-phase high-performance liquid chromatographic method, based on the design of the experiment approach, was developed for the simultaneous determination of capsiate isomers. Critical method parameters, i.e., flow rate and mobile phase composition, demarcated during preliminary screening were optimized using central composite design. Chromatographic separation was achieved on a Nucleodur C18 column (250 × 4.6 mm, 5 μm), with the mobile phase consisting of water–acetonitrile (40:60), both acidified with 0.1% v/v formic acid, passed at a flow rate of 1 mL/min. E- and Z-capsiates were eluted from the column at the retention times of 18.56 ± 0.09 and 17.30 ± 0.08 min, respectively, with a resolution factor of 1.693 ± 0.046. The method was found to be linear within the concentration range of 1.054–5.270 and 8.623–43.115 μg/mL for Z- and E-isomers, respectively, with an R2 of >0.99. Recovery of the individual values was in range of 96.15–101.92%, with a relative standard deviation of <2%. The developed method was used to quantify capsiate isomers extracted from sweet pepper fruits. Therefore, the proposed method is presented for optimum isomeric resolution of these closely related E- and Z-isomers with convenient sample preparation, acceptable run-time, cost effectiveness and use of conventional instruments. Highlights
Abstract: The maintenance of diversity is, from a genetic perspective, one of the key aims in a conservation program. Because the most widely used measure of genetic diversity is the expected heterozygosity of the population, or gene diversity (GD), most research has been devoted to finding optimal strategies for maximizing this parameter. Little attention has been paid, however, to the development of strategies to manage allelic diversity (AD), the number of alleles maintained in the population. Using computer simulations, we show that the strategies that maximize GD, by managing contributions from parents, keep levels of AD as high as strategies maximizing AD itself, for a wide range of situations including different numbers of molecular markers used and the possibility of evaluating a number of offspring per parent to make decisions. Because maximization of GD also minimizes levels of inbreeding, this should be the strategy of choice in any conservationprogram.
Flavonoids undergo substantial hepatic metabolism and the metabolites might significantly contribute to the effects of these dietary constituents. The metabolites of flavonoids in liver can be summarized as follows: 1) For flavones, the hydroxylation appears to occur at the C-4'-, C-3', C-6 and C-8- position when there is a single or no hydroxy group on the B-ring. The methoxyl groups positioned at the C-7, C-6 or C-4'- position of flavones are demethylated. The glucuronidation occurs at the 6, 7, 4' or 3'- hydroxyl moiety. Flavone glycosides and aglycones appear to undergo similar metabolic pathways. 2) For flavonols, the hydroxylation appears at the 3' and 4'- position and flavonols with a 4'-methoxy group are easily O-demethylated to their corresponding hydroxylated analogs. The glucuronidation takes place at the 7, 3, 3' and 4'- hydroxyl moiety. 3) For isoflavones, the microsomal hydroxylation is observed at the C-3'-, C-6 and C-8- position when there is a single or no hydroxy group on the B-ring. The demethylation takes place at the C-6- or C-4'- position when there is one methoxy group on C-4' or C-6-position, respectively. The glucuronidation occurs at the 4, or 5- hydroxyl moiety. 4) For chalcones, the C-3'-, and C-8- positions undergo hydroxylation. The C-8- position is a very active site for metabolism of chalcones.
The relationship between the proanthocyanidin profile and the perceived astringency was assessed in 13 commercial Tempranillo red wines. The concentration and compositional information were obtained by liquid chromatography with diode array detection coupled to electrospray ionization mass spectrometry after acid-catalyzed depolymerization of wine proanthocyanidins in the presence of excess phloroglucinol. Statistical analysis of the results showed significant correlations between sensory and chemical determinations. Astringency was more affected by the subunit composition than by the total concentration or the average degree of polymerization of wine proanthocyanidins. Higher proportions of epicatechin (EC) subunits in extension positions and gallocatechin (GC) subunits in terminal positions were shown to increase astringency. On the contrary, the amount of epigallocatechin (EGC) in both extension and terminal positions was negatively correlated with the perceived astringency.
A study was conducted to develop a optical response model of highly faceted metal nanoparitcles by using a 3D boundary element method (BEM). The study also can be used to develop model for rod-to-octahedron transition. The BEM for axially symmetric particles can provide optical spectra in decorated nanorods, decahedrons, and nanostars. Gold nanorods were synthesized during the study in water and transfer into N,N-dimethylformamide (DMF). The study also examine the chemical growth of axially symmetric gold nanorods into octahedrons. It was observed during the study that the modeling of the cross-section is simple for a cylinder, while modeling of cross-section of prism require total width and the curvature of the edges. The study concluded that this method is computationally more efficient the DDA of FDTD techniques. © 2008
