Veronika Nagy

Gram-scale synthesis of a glucopyranosylidene-spiro-thiohydantoin and its effect on hepatic glycogen metabolism studied in vitro and in vivo

Abstract A high yielding, simple synthesis is described starting from d -glucose to produce gram quantities of a glucopyranosylidene-spiro-thiohydantoin. This compound efficiently inhibited the activity of rat liver glycogen phosphorylase a ; moreover, it also activated phosphorylase phosphatase which, in turn, decreased the amount of glycogen phosphorylase a . Both effects result in the inhibition of glycogen mobilization and the formation of glucose from glycogen.

Hydrophilic carotenoids: Recent progress

Carotenoids are substantially hydrophobic antioxidants. Hydrophobicity is this context is rather a disadvantage, because their utilization in medicine as antioxidants or in food chemistry as colorants would require some water dispersibility for their effective uptake or use in many other ways. In the past 15 years several attempts were made to synthetize partially hydrophilic carotenoids. This review compiles the recently synthetized hydrophilic carotenoid derivatives.

Isolation and purification of acid-labile carotenoid 5,6-epoxides on modified silica gels

INTRODUCTION The acid-labile carotenoid 5,6-epoxides occur in all green plants and in most fruits, but their isolation or purification is complicated and expensive because they decompose on normal silica gels. Alkaline stationary phases in open column chromatography (OCC) have low capacities, which makes them unsuitable for preparative scale. OBJECTIVE To find a simple high-capacity stationary phase for OCC that does not induce transformations of acid-labile compounds. METHODOLOGY Commercially available silica gel was treated with aqueous sodium bicarbonate solution to neutralise its slightly acidic character, and was then washed and dried. The effect of the treated gel (named silica-9) on violaxanthin was studied. The modified gel was also applied to the OCC of different complex natural extracts (maple leaves and fruits of yellow paprika). Carotenoids were examined by HPLC-PAD both before and after chromatography on the modified gel. RESULTS Violaxanthin decomposed rapidly on normal silica gels but not on the modified gel. Chromatography of plant extracts showed that the modified gel had a similar capacity to the untreated gel but did not effect epoxy-carotenoids, which could be separated or enriched readily on a large scale. CONCLUSION The modified gel does not induce any transformation or decomposition of epoxy-carotenoids but still exhibits a high capacity, suggesting that it can be used in preparative organic chemistry as an additional and convenient tool in the OCC for the separation of other acid-labile compounds.

Carotenoid Composition of the Fruit of Red Mamey ( Pouteria sapota )

The detailed carotenoid analysis of red mamey (Pouteria sapota) was achieved by HPLC-DAD-MS, chemical tests, and cochromatography with authentic samples. Altogether 47 components were detected and 34 identified from the total extract or after fractionation with column chromatography. The main carotenoids were cryptocapsin, sapotexanthin, and capsanthin 5,6-epoxide. Some further minor components containing the κ-end group with or without a hydroxy group and their 5,6-epoxy precursors were identified. Some comments are made about the biosynthesis of κ-carotenoids in red mamey.