Charles W. Nagel

Analysis of phenolic acids and flavonoids by high-pressure liquid chromatography☆

Abstract A high-pressure liquid chromatographic (HPLC) technique for the separation and quantitation of three classes of naturally occurring phenolic compounds has been developed. Investigated were a series of phenolic acids, both cinnamic and benzoic, and a variety of flavone compounds including flavones, flavonols, and flavanones as well as glycosylated flavone derivatives with mono- and disaccharide substitution. The effects of structural variations within the phenolic compounds upon elution order and retention were elaborated. The technique offers selectivity, resolution, speed, and sensitivity (minimum detectable amounts below 50 ng) far superior to classical techniques such as paper chromatography. Time of analysis by the HPLC technique is measured in minutes while an equivalent analysis by classical techniques would require several days, if not weeks.

High-pressure liquid chromatographyic analysis of hydroxycinnamic acid—tartaric acid esters and their glucose esters in vitis vinifera

Abstract A high-pressure liquid chromatographic technique has been developed to separate and quantify the amount of monocaffeoyl, mono-p-coumaroyl-, and monoferuloyl-tartaric acid in grapes. The method features direct analysis of the grape juice with minimum sample preparation. The identity of the hydroxycinnamic acid—tartaric acid esters has been established through hydrolysis of the esters followed by gas—liquid chromatography and high-pressure liquid chromatography. The absence of chlorogenic and neochlorogenic acids often reported in grapes has been substantiated. Evidence will be presented for the occurrence of an ester of caffeic acid—glucose—tartaric acid.

The isolation of oligogalacturonic acids by column chromatography

Abstract A series of oligogalacturonic acids, including di-, tri-, tetra-, penta-, hexa-, hepta-, and octa-galacturonic acids and unsaturated di-, tri-, tetra-, and pentagalacturonic acids, were produced by enzymic cleavage of pectic acid and separated by ion exchange column chromatography. Evidence for their purity was presented.

High-pressure liquid chromatographic separation of the naturally occurring toxicants myristicin, related aromatic ethers and falcarinol☆

The naturally occurring toxicants myristicin, twelve related aromatic ethers and the toxic acetylenic alcohol, falcarinol, were separated from one another by high-pressure liquid chromatography (HPLC). The technique employed a microparticulate nitrile phase column and used heptane and tetrahydrofuran as the eluting solvents. Preparative HPLC with 5-micrometer silica allowed isolation of gram quantities of parsleyapiole and dillapiole from extracts of plain parsley seeds and dill seeds, respectively. Commercially available myristicin as well as other aromatic ethers were also purified in gram quantities with the preparative column.

Microbial degradation of gum karaya.

Abstract Gum karaya (Sterculia urens gum) was degraded by a fungal isolate, a Cephalosporium sp. The patterns of carbohydrate utilization and enzyme secretion by the organism growing on the purified polysaccharide were determined, together with the ratio of neutral sugars present in the gum. Cephalosporium growth-studies indicate that the gum contains at least three different types of chains. One chain (50% of the total polysaccharide) is postulated to contain repeating units of four galacturonic acid residues containing β- D -galactose branches and having an L -rhamnose residue at the reducing end of the unit. A second chain (17% of the polysaccharide) contained 50% of galacturonic acid, 40% of rhamnose, and 10% of galactose by weight and is postulated to contain an oligorhamnan chain, containing D -galacturonic acid branch-residues, and interrupted occasionally by a D -galactose residue. D -Glucuronic acid is apparently confined to a third type of chain, comprising 33% of the polysaccharide.