Ι. Απομόνωση και ταυτοποίηση δευτερογενών μεταβολιτών από τα φυτά: Centaurea zuccariniana DC. και Origanum vulgare L. ssp. hirtum. Βιολογικές δοκιμασίες in vitro. ΙΙ. Μοριακή προσομοίωση: εφαρμογή και μελέτη στις απομονωμένες ουσίες

Abstract

In the present thesis, two main objectives were achieved: 1) isolation and identification of secondary metabolites from Centaurea zuccariniana DC. and Origanum vulgare L. ssp. hirtum, 2) application of molecular modeling techniques on the isolated compounds. From the aerial part of Centaurea zuccariniana DC. seventeen compounds have been isolated: four sesquiterpene lactones, 8a-(3,4-dihydroxy-2-methylene-butanoyloxy) dehydromelitensine, cnicin, 4'-acetylcnicin, 8a-hydroxy-sonchucarpolide, one lignan, arctiin, twelve flavonoids i.e. apigenin, genkwanin, hispindulin, cirsimaritin, cosmoside, luteolin-7-Ο-β-D-glucoside, 5, 4'-dihydroxy-7-methoxyflavonol, kaempherol-3-O-β-D-glucoside, 6-hydroxy-apigenin-7-O-β-D-glucoside, 6-methoxy-kaempherol-3-O-β-D-glucoside, luteolin-4'-Ο-β-D-glucoside, 6-methoxy-apigenin-7-O-β-D-glucoside. The eudesmanolide 8a-hydroxy-sonchucarpolide was a new natural product. The cytotoxic activity of the isolated sesquiterpene lactones was tested against the following cell lines: DLD1, SF268, MCF7, H460 and OVCAR3. All tested compounds exhibited mainly cytostatic activity. 8a-(3,4-dihydroxy-2-methylene-butanoyloxy) dehydromelitensine was found to be the most active. 4'-acetylcnicin differing from cnicinin at position 4', is less active, suggesting that the substitution of the 8a-acyl side chain is important for the activity. The eudesmanolide was innactive. In an attempt to identify topoisomerase I as a possible target for the exhibition of their cytotoxic activity, a docking study on the binding sites of the studied sesquiterpene lactones on topoisomerase I was undertaken (Koukoulitsa et al., 2002). The prediction of the pharmacokinetic profile of several antifungal sesquiterpene lactones, isolated from Greek taxa of Centaurea sp., was undertaken using the VolSurf procedure. The molecules were projected on the following pre-calculated ADME models: Caco-2 cell permeability, plasma protein affinity, blood-brain barrier permeation and thermodynamic solubility. The in silico projection revealed a non optimal pharmacokinetic profile for the studied compounds. ADME in silico screening of a semi-synthetic derivatives virtual library has been performed in order to optimize the pharmacokinetic properties. A number of derivatives were proposed, as it was predicted to have higher Caco-2 cell permeability, while the pharmacokinetic behaviour regarding BBB penetration, protein binding and solubility was mainly preserved (Koukoulitsa et al., 2005a). It is well known that the activity of a given sesquiterpene lactone may be determined by the availability and accessibility of vitally important thiol compounds present in specific fungi, such as cysteine and glutathione. A simulation study of the interaction of the sulfhydryl nucleophiles with two germacranolides, selected from a series of natural antifungal sesquiterpene lactones and corresponding semi-synthetic derivatives, was performed through molecular modeling techniques. The Hartree-Fock ab initio calculations revealed that structural modification of the examined natural sesquiterpene lactones may increase their biologic activity (Koukoulitsa et al., 2006a). ..............................................................................................................................................