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Universita' Degli Studi Di Napoli UNIVERSITA' DEGLI STUDI DI NAPOLI "FEDERICO II" DOTTORATO DI RICERCA IN "SCIENZA DEL FARMACO" XXIV CICLO 2008-2011 ISOLATION AND STRUCTURE ELUCIDATION OF BIOACTIVE SECONDARY METABOLITES FROM MARINE AND TERRESTRIAL ORGANISMS Dr. Giuseppina Chianese Tutor Coordinatore Prof. O. Taglialatela-Scafati Prof.ssa M. V. D‘Auria Index 1 INDEX Abstract (English) ......................................................................................... page 5 Abstract (Italian) ........................................................................................... page 7 CHAPTER I - INTRODUCTION ............................................................... page 9 1.1. Natural Products Chemitry ................................................................... page 9 1.1.1 An historical perspective .............................................................. page 10 1.1.2 Marine Natural Products .............................................................. page 13 1.2. Structural determination methods ..................................................... page 14 1.2.1 Mass spectrometry ....................................................................... page 15 1.2.2 Nuclear Magnetic Resonancects .................................................. page 17 1.3. Methods for configuration determination ......................................... page 18 1.3.1 Circular Dichroism ....................................................................... page 19 1.3.2 Computational methods for configuration determination ............ page 20 References .................................................................................................... page 22 Publication of the candidate during the Ph.D. period ............................. page 24 CHAPTER II - CANNABINOIDS: ISOLATION AND SYNTHESIS OF NEW COMPOUNDS .................................................................................. page 26 2.1. Phytochemistry and Medicinal Chemistry of Cannabinoids .......... page 26 2.1.1 Cannabigerol-type ........................................................................ page 30 2.1.2 Cannabichromene- and cannabicyclol-type ................................. page 31 2.1.3 Cannabidiol- cannabielsoin- and cannabimovone-type ............... page 31 2.1.4 Tetrahydrocannabinol-type .......................................................... page 34 Index 2 2.1.5 Cannabicoumaronone- and cannabichromanone-type ................. page 35 2.2. Cannabinoid receptors......................................................................... page 36 2.3. Cannabioxepane, a novel tetraciclic cannabinoid from hemp, Cannabis sativa L. ................................................................................................. page 41 2.3.1 An ancient plant ........................................................................... page 41 2.3.2 Extraction, isolation and structure elucidation ............................. page 43 2.3.3 Affinity of the cannabioxepane for cannabinoid receptors ......... page 49 2.3.4 Experimental ................................................................................ page 51 2.4. Steroidal CB receptor ligands from the Indonesian sponge Dasychalina sp. ........................................................................................................... page 53 2.4.1 Introduction .................................................................................. page 53 2.4.2 Extraction, isolation and structure elucidation ............................. page 54 2.4.3 Preparation of semisynthetic derivatives of haplosamate A ........ page 56 2.4.4 Experimental ................................................................................ page 59 References .................................................................................................... page 62 CHAPTER III - ISOLATION AND SYNTHESIS OF NEW ANTIMALARIAL COMPOUNDS ........................................................... page 67 3.1. Malaria .................................................................................................. page 67 3.2. Antimalarial endoperoxides ................................................................ page 70 3.3. Synthesis of simplified antimalarial endoperoxides .......................... page 78 3.3.1 In vitro antimalarial activity ......................................................... page 84 3.3.2 Reaction with Fe(II) chloride ....................................................... page 85 3.3.3 Structure-Activity Relationship Studies ...................................... page 88 3.3.4 Experimental ................................................................................ page 90 Index 3 3.4. Antimalarial limonoids from the neem plant (Azadirachta indica) . page 99 3.4.1 Isolation and structure elucidation of new secondary metabolities .......... .............................................................................................................. page 101 3.4.2 Pharmacological activity ............................................................ page 106 3.4.3 Experimental .............................................................................. page 108 References .................................................................................................. page 110 CHAPTER IV - DITERPENOIDS FROM PLANTS OF THE FAMILY EUPHORBIACEAE ................................................................................. page 114 4.1. Secondary metabolites from root barks of Jatropha curcas .......... page 120 4.1.1 Introduction ................................................................................ page 120 4.1.2 Isolation and structure elucidation of new secondary metabolities .......... .............................................................................................................. page 121 4.1.3 Spirocurcasone, a diterpenoid with a novel carbon skeleton .... page 123 4.1.4 Pharmacological activity ............................................................ page 127 4.1.5 Experimental .............................................................................. page 127 4.2. Diterpenoids from the Iranian plant Euphorbia macroclada Boiss.page 132 4.2.1 Introduction ................................................................................ page 132 4.2.2 Pre-myrsinane derivates ............................................................. page 132 4.2.3 Tigliane derivates ....................................................................... page 136 4.2.4 Experimental .............................................................................. page 140 4.3. Diterpenoids from the Iranian plant Euphorbia bungei Boiss. ...... page 145 4.3.1 Introduction ................................................................................ page 145 4.3.2 Structure elucidation .................................................................. page 145 4.3.3 Experimental .............................................................................. page 152 References .................................................................................................. page 154 Index 4 CHAPTER V – SUPPORTING DATA ................................................... page 157 5.1. General methods ................................................................................ page 157 5.2. NMR spectra ....................................................................................... page 158 5.3. Computational details of compounds 57-63 ..................................... page 176 5.4. Computational details of compound 76 ........................................... page 178 ACKNOWLEDGMENTS ................................................................ page 180 5 ABSTRACT Natural products have historically been a rich source of ―lead compounds‖ in drug discovery. The investigation of terrestrial plants and marine organisms aimed at searching new biologically active compounds is a central issue of this kind of studies, trough structure elucidation combined with biological tests. My research work, described in this PhD thesis, is included in this research topic and was addressed at three different topics: - cannabinoids from Cannabis sativa and from the Indonesian sponge Dasychalina sp.; - isolation and synthesis of antimalarial compounds; - metabolites isolated from plants belonging to the Euphorbiaceae family (Jatropha curcas, Euphorbia macroclada and Euphorbia bungei). A phytochemical investigation of the fibre cultivar of Cannabis sativa derived from the historical Carmagnola variety led to isolation of the novel spiranic stilbenoid isocannabispiradienone and the biphenyl-type cannabinoid cannabioxepane (CBX), a tetracyclic compound characterized by an unprecedented C-5/C-8‘ oxygen bridge and devoid of cannabinoid activity. In the same area, from the polar organic extract of the Indonesian sponge Dasychalina sp., I have isolated haplosamate A, a unique C28 sterol containing a sulfate group at C-3 and a methyl phosphate at C-15, along with its new desulfo analogue. Both compounds, as well as their semi-synthetic analogues, have been evaluated for interaction with CB1 and CB2 receptors through a binding test. Desulfohaplosamate showed a selective affinity for CB2 receptors in the low μM range. Haplosamate derivatives represent the first CB receptor ligands belonging to the class of steroids. The search for antimalarial lead compounds is another main topics of my Ph.D. activity discussed in this thesis. On the bases of the previously developed
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