Special Issue "Triterpenes and Triterpenoids"

Guest Editor
Prof. Dr. Vassilios Roussis
University of Athens, School of Pharmacy, Department of Pharmacognosy and Chemistry of Natural Products, Panepistimiopolis Zografou, GR 15771, Athens, Greece
E-Mail:
Phone: +30 210 7274 592
Fax: +30 210 7274 592
Interests: marine natural products; chemotaxonomy; chemical ecology

• natural product chemistry and medicinal chemistry of triterpenes and triterpeniods
• squalene
• material science
• biomaterials
• bioassay
• pharmacological activity
• medicinal plant
• herb
• herbal medicine
• chinese medicine
• fungus
• mushroom

Manuscript ID: molecules-triterp-20080922-es-Martin
Type of Paper: Article
Title: Clavaric acid and fasciculic acid: Biosynthesis and Molecular Genetics
Authors: Juan F. Martín ^1,2 and Ramiro P. Godio ²
Affiliations: ¹ Área de Microbiología, Facultad de Ciencias Biológicas y Ambientales, Universidad de León, Campus de Vegazana, s/n. 24071 León, Spain
² Instituto de Biotecnología de León (INBIOTEC), Avda. Real, 1. 24006 León, Spain
E-mail: jf.martin@unileon.es
Abstract: Clavaric acid is a potent antitumor agent produced by the mushroom-forming basidiomycete Hypholoma sublateritium. Clavaric acid is structurally similar to fasciculic acid, a related triterpenoid produced by Hypholoma fasciculare that is described as a calmodulin inhibitor.
These two compounds are derived from squalene by the action of enzymes that convert squalene to 2,3-dioxidesqualene and this intermediate to clavarinone, a direct precursor of clavaric acid or fasciculic acid. One of these enzymes, the squalene oxidase, is common for primary metabolism (ergosterol biosynthesis) and secondary metabolism, whereas the late enzymatic steps are specific for the biosynthesis of clavaric acid and fasciculic acid. Molecular genetics studies allowed us to clone and characterise the genes encoding these enzymes. These studies have provided a considerable insight into the biosynthesis of triterpenoids in fungi, providing new potent pharmacologically-active compounds. Squalene epoxidases and oxidosqualene cyclases with modified consensus motifs in their active centers appear to play an important role in determining the oxidation and modification reactions that may result in specific secondary metabolites.

Manuscript ID: molecules-triterp-20080930-us-Nes
Type of Paper: Article
Title: Steroidal Triterpenes: Design of Substrate-based Inhibitors of Ergosterol and Sitosterol Synthesis
Authors: Jialin Liu and W. David Nes
Affiliation: Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
E-mail: WDNES@aol.com
Abstract: This article reviews the design and study, in our own laboratory and in other laboratories, of new steroidal triterpenes with a modified lanosterol or cycloartenol frame. These compounds, along with a number of known analogs with the cholestane skeleton, have been evaluated as reversible or irreversible inhibitors of sterol C-24 methyltransferase (SMT) from plants, fungi and protozoa. The SMT catalyzes the C24-methylation reaction involved with the introduction of the C24-methyl group of ergosterol and the C24-ethyl group of sitosterol, cholesterol surrogates that function as essential membrane inserts in many photosynthetic and non-photosynthetic eukaryotic organisms. Sterol side chains constructed with a nitrogen, sulfur, bromine or fluorine atom or altered to possess a methylene cyclopropane group, or elongated to include terminal double or triple bonds are shown to exhibit different in vitro activities toward the SMT which are mirrored in the inhibition potencies detected in the growth response of treated cultured human and plant cells or microbes. Several of the substrate-based analogs surveyed here appear to be taxa-specific compounds acting as mechanism-based inactivators of the SMT, a crucial enzyme not synthesized by animals. Possible mechanisms for the inactivation process and generation of novel products catalyzed by the variant SMTs are discussed.

Manuscript ID: Molecules-triterp-20081024-Akhmetova
Type of paper: Review
Title: Pentacyclic Triterpenes and Their Synthetic Transformations
Authors: Vnira R. Akhmetova, Elvira R. Shakurova
Affiliciation: Institute of Petrochemistry and Catalysis, Russian Academy of Sciences, 141 prosp. Oktyabrya, 450075, Ufa, Russian Faderation.
E-mails: vnirara@mail.ru, shakurovaer@mail.ru,ink@anrb.ru
Abstract: Literary data on polycyclic triterpenoids and own experimental results on separation, X-ray researches and synthetic transformations of pentacyclic triterpenoids from Scotch thistle Onopordum acanthium L. growing in the south of the Ural mountains (Russia) are generalized.
Triterpenoids rather widespread occure in nature. Their molecules containing six isoprenoid links, are predecessors of steroids, both in animals, and in plant organisms. Practically all plants produce tetra-and pentacyclic triterpenes metabolites with various types of a carbon skeleton. Among pentacyclic triterpenes 10 structural types are revealed. In a medical practice pentacyclic triterpenoids are already successfully applied in composition of regulators of cardiovascular system, antibacterial and anti-AIDS preparations, and in glycosylate form (saponin) in composition of hypochilesterinemic preparations and for hemosorption superfluous serum cholesterin from blood. Complete biological potential of polycyclic triterpenoids as medical products is still not studied. In this review there were summaried the various types of plant pentacyclic triterpenoids that have been described in the literature, such as oleanane, ursane, taraxastane and lupan (section 1); information about on biological activity (section 2), and also information available in the literature about chemical modifications triterpenoids and biological activity of their synthetic analogues (section 3). In the present review literary information for the past of 15-20 years is observed. The bibliographic list contains about 150 titles.