Cristiana Melchioni

Microcomponents of olive oil—III. Glucosides of 2(3,4-dihydroxy-phenyl)ethanol

Abstract The molecular structure of the microcomponents of olive fruit was investigated in order to evidence new molecules which could be transferred to the resulting oil and therefore be typical of olive oil. The three glucosides of 2(3,4-dihydroxy-phenyl)ethanol, 1 , 2 and 3 were isolated together with other glucosides previously identified in Olea europaea . Glucosides 1–3 were detected in the olive oil, there being always present a small quantity of water as an emulsion, together with the aglycone, the 2(3,4-dihydroxy-phenyl)ethanol. The presence of glucosides 1–3 is closely linked with the organoleptic characteristics and to the recognized antioxidant properties of olive oil..

Microcomponents of olive oil. Part II: Digalactosyldiacylglycerols from Olea europaea

Two galactolipids, 1 and 2, were isolated and identified both in olive fruits and in olive oil. They are characterized by a low polarity, despite the presence of a diglycosidic unit, giving, in water, micelles. Because of this characteristic, compounds 1 and 2 could be responsible for the stability of the light emulsion typical of freshly produced olive oil. The presence of hydrophilic ortho-diphenolic compounds enhances the antioxidant properties of this oil, particularly in the first period after the production. In addition, the functions present in 1 and 2 are susceptible to hydrolysis and may be easily modified in the alkaline treatment used for the olive oil refining process. For this reason, their presence in olive oil may be a very useful indication of the untreated food product.

Synthesis of a carbocyclic sialic acid analogue for the inhibition of influenza virus neuraminidase.

The influenza virus neuraminidase (NA) is essential for viral infection and offers a potential target for antiviral drug development. We prepared a carbocyclic sialic acid analogue, potentially able to inhibit NA. Its structure is an analogue of the transition-state of the reaction catalysed by NA. As starting material, quinic acid was selected owing to its ready availability and its stereochemical feature suitable for the target structure. The quinic acid was first converted in the shikimic acid; then two of the three hydroxyl functions of this product were selectively functionalised to obtain the target molecule (3R,4S,5R)-4-acetamido-3-guanidino-5-hydroxycyclohex-1-ene-1-carboxylic acid.

A new method of regioselective protection of primary alcoholic function with rare earths salts

Abstract Regioselective acetylation of primary alcoholic functions, in the presence of secondary ones, was performed in very high yield with methyl ortoacetate, by means of catalysis with rare earths salts on silica gel.

Phenolic components of Olea europaea--isolation of tyrosol derivatives.

A new tyrosol derivative, the oleic ester of tyrosol, was isolated from fruits of Olea europaea, Cassanese cultivar. Salidroside, the known glucosyl derivative of thyrosol, was isolated from the Carolea cultivar.

Chiral Synthons from the Iridoid Glucoside Antirrhinoside − Synthesis of a Carbocyclic Homonucleoside Analogue

The synthetic modification of the natural cyclopentanoid monoterpene glucoside antirrhinoside is reported. Some stereoselective modifications have been performed on the bicyclic iridoidic ring, resulting in opening of the dihydropyran ring. A series of chiral synthons having a highly oxygenated cyclopentanoid ring has been prepared, which could be used in the synthesis of nucleoside analogues. We describe herein the synthesis of an acyclovir derivative (DA-146) as an example.

Iridoids from Seeds of Gentiana Lutea

In the seeds of Gentiana lutea L. there were also detected, in addition to the known sweroside and getiopicroside, loganic acid 3 and trifloroside 4 that is present as main glycosidic component. The structures of 3 and 4 were established by spectroscopic studies.

Aromatic sialic acid analogues as potential inhibitors of influenza virus neuraminidase

The influenza virus neuraminidase (NA) is an enzyme essential for viral infection and offers a potential target for antiviral drug development. We aimed our research at the synthesis of non-carbohydrate molecules able to inhibit NA as transition-state analogues. Aromatic sialic acid analogues (compound 5 and compound 10) were synthesised in good yields starting from commercially available benzoic acids using a suitable synthetic strategy.

Iridoid glucosides from Lamium garganicum flowers.

In the flowers of Lamium garganicum L. a single iridoid is present, as main glycosidic component, the 8-acetyl-shanzhiside methyl ester, 1. The structure of 1 was established by spectroscopic studies and chemical evidence.

Neuraminic acid — Structure, Chemistry, Biological Activity

Abstract The interest in the sialic acids chemistry has rapidly increased in last years, especially since their involvement in the regulation of a great variety of biological phenomena was recognised. In this paper we are interested in the biological function of sialic acid that it is able to interact with biomolecules, as well as viruses are. In particular, during influenza infection, the virus attaches cell surface receptors containing sialic acids. Haemagglutinin (HA) and neuraminidase (NA) are two major surface glycoproteins expressed by both influenza A and B viruses. HA is knownto mediate binding of viruses to target cells via terminal sialic acid residues in glycoconjugates. This binding is the first step of viral infection. In contrast to HA activity, the NA catalyses removal of terminal sialic acids linked to glycoproteins and glycolipids. The NA activity is necessary in the elution of newly formed viruses from infected cells and may also promote viralmovement through respiratory tract mucus, thus enhancing viral infectivity. Therefore, HA and NA have been considered to be a suitable target for developing agents against influenza infection. The first approach in the design of high affinity inhibitors has been to use sialic acid as a scaffolding, modifying its functional groups in order to increase the affinity of the sialic acid cell receptor analogue to the HA; a second approach has concerned the partial and total syntheses of sialic acid analogues potentially able to inhibit the receptor — destroying activity of NA.