The present volume contains 22 articles written by leading experts in natural product chemistry on biologically active natural products. It includes research on a variety of different classes of natural products including sesquiterpenes, quassinoids, diterpenoids, lignans, oligostilbenes, phenylethanoids, phenylpropanoid glycosides, curcumin analogues, glycosphingolipids etc. Many of these have been found to be active in a number of different disease conditions.

* Timely reviews written by international authorities in the field
* Topics ranging from purely chemical to very biological
* The 13th volume in the series to be devoted to bioactive natural products

Atta-ur-Rahman, Professor Emeritus, International Center for Chemical and Biological Sciences (H. E. J. Research Institute of Chemistry and Dr. Panjwani Center for Molecular Medicine and Drug Research), University of Karachi, Pakistan, was the Pakistan Federal Minister for Science and Technology (2000-2002), Federal Minister of Education (2002), and Chairman of the Higher Education Commission with the status of a Federal Minister from 2002-2008. He is a Fellow of the Royal Society of London (FRS) and an UNESCO Science Laureate. He is a leading scientist with more than 930 publications in several fields of organic chemistry.

Guido Jach; Jochen Winter Max-Planck-Institut für Züchtungsforschung Carl von Linne-Weg 10, 50829 Cologne, Germany

A number of fluorescent proteins have been discovered in marine organisms with the green-fluorescent protein (GFP) from Aequorea victoria representing the first member of this family being isolated and well characterized. These polypeptides show marked differences in their spectral properties. Today, blue-, yellow-, cyan- and red-light emitting proteins are known in addition to GFP.

These natural products possess the unique ability to autocatalytically form a cyclized p-hydroxybenzylidene-imidazolidinone structure acting as a light emitting chromophore in the presence of the suitable environment provided by ß-can 3D-structure of the proteins. Fluorescence actually represents the biological activity of these protein. In fact, this intrinsic protein property allows for their non-invasive non-destructive detection in living cells, an ability that has caused enormous interest on all areas of molecular biology employing reporter proteins for gene expression and protein localization studies. Today, GFP is widely used and well accepted as valuable reporter protein.

However, during the last decade a number of GFP mutants were described showing altered spectral properties and/or improved solubility upon expression in heterologous systems. In addition, numerous other naturally occurring fluorescent proteins were described such as the red-fluorescent protein from Discosoma sp. (DsRED). A comprehensive description of the available fluorescent proteins is given including the spectral properties, amino-acid sequence alignments, comparisons of the secondary and tertiary structures of the proteins.

The mechanisms for this self-catalyzed amino-acid modifications leading to the chromophore formation are best characterized for the GFP although some work was carried out on other proteins as well. This review describes the current knowledge about maturation and (possible) oligomerization of the proteins.

Numerous marine invertebrates display an extensive palette of visible fluorescence and coloring. In part, the vibrant coloration is due to a growing family of intrinsically fluorescent proteins. Genes encoding fluorescent proteins have been isolated and described for a variety of coelenterates, both hydrozoa such as Aequorea, Obelia, and Phialidium, and anthozoa such as Anemonia, Discosoma and Renilla.

Amongst the fluorescent proteins known today the green-fluorescent protein (GFP) from the jellyfish Aequorea victoria not only represents the first member of this protein family being isolated it also is by far the best understood fluorescent protein. Its history dates back to 1962 when it was first observed as a companion protein to Aequorin (a blue-light emitting chemiluminescent Aequorea protein), exhibiting a bright, greenish fluorescence when excited with ultraviolet light [1]. Soon after that the first emission spectrum of GFP was published by the same group [2]. Interestingly, the light emission of GFP peaked at 508 nm a value that is rather close to the green bioluminescence peak of living Aequorea tissue. In addition, the excitation spectrum of GFP showed a (secondary) peak around 470 nm, which overlaps with the blue chemiluminescence peak produced by Aequorin. Based on these data it was assumed that the green glow of intact Aequorea tissues results from the conversion of the blue light emission of Aequorin into green light by GFP.

Later on similar color shifts were found in the related coelenterates Obelia (a

Foreword
Preface
Contributors
Focus on fluorescent proteins
Structure, function and mode of action of select arthropod neuropeptides
Natural products as modulators of apoptosis and their role in inflammation
Sesquiterpenes classified as phytoalexins
Bioactive triterpenes and related compounds from celastraceae
Structure-activity relationships of sesquiterpene lactones
Synthetic investigations in the field of drimane sesquiterpenoids
Quassinoids: Structure diversity, biological activity and synthetic studies
The diterpenoids from the genus Sideritis
Recent developments in the asymmetric synthesis of lignans
Natural oligostilbenes
Isolation, structure elucidation and bioactivities of phenylethanoid glycosides from Cistanche, Forsythia and Plantago plants
Pharmacological activities of phenylpropanoids glycosides
Development of tubulin inhibitors as antimitotic agents for cancer therapy
Cholesterol biosynthesis inhibitors of microbial origin
Structure-activity relationships of curcumin and its analogs with different
biological activities
The Vinca alkaloids: From biosynthesis and accumulation in plant cells,
to uptake, activity and metabolism in animal cells
The chemistry of Olea Europaea
The chemistry of the genus Cicer L.
New research and development on the Formosan annonaceous plants
Structural and functional aspects of fungal glycosphingolipids
Phytochemical studies and pharmacological activities of plants in genus Hedyotis/Oldeanlandia
Subject Index