• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 46
  • 33
  • 6
  • 6
  • 5
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 97
  • 28
  • 15
  • 14
  • 10
  • 10
  • 9
  • 8
  • 8
  • 8
  • 7
  • 7
  • 7
  • 7
  • 7
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

The Studies of Chemical Constituents and their Biological Activities from the Formosa Soft Coral Cladiella krempfi

Tai, Chi-jen 25 August 2010 (has links)
Eighteen eunicellin-based diterpenoids were isolated from the organisms of the soft coral Cladiella krempfi. According to the results of 1D and 2D NMR spectroscopic experiments, the structures of these marine natural products were established. Among them, krempfielins A¡VJ (1¡V10) are new compounds, and sclerophytin B (11), sclerophytin F (12), litophynols A (13), (1R*, 2R*, 3R*, 6S*, 7S*, 9R*, 10R*, 14R*)-3-butanoyloxycladiell-11(17)-en-6,7-diol (14), litophynin I monoacetate (15), (1R*, 2R*, 3R*, 6S*, 9R*, 10R*, 14R*)-3- acetoxycladiell-7(16)-11(17)-dien-6-ol (16), 6-acetoxy litophynin E (17) and litophynin F (18) are the previously isolated compounds. The anti-inflammation activity of these compounds at 10 £gM was studied. The results showed that 9, 14 and 17 effectively inhibited more than 80% expression of iNOS protein in LPS stimulated RAW 264.7 macrophage cells, and 5, 6, 10, 13 and 18 inhibited more than 60% expression of iNOS protein. Also, 9, 12, 16 and 18 were found to inhibit the expression of COX-2 protein in LPS stimulated RAW 264.7 macrophage cells to 52.5, 79.2, 82.2 and 48.2%. Cytotoxicity of these compounds were tested by the MTT assay using five human cancer cell lines (A549, BT483, H1299, Hep3B and SAS) and one normal cell line, BEAS2B. Compounds 9, 10, 11, 14, 17 and 18 were shown to exhibit cytotoxic activity.
22

Structure elucidation and oxidation chemistry of natural products /

Sy, Lai-king. January 1998 (has links)
Thesis (Ph. D.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 223-236).
23

Isolation, Characterization, and Synthesis of Bioactive Natural Products from Rainforest Flora

Berger, John Michael 11 July 2001 (has links)
As part of our ongoing investigations for anticancer drugs from rainforestflora, five plant extracts were determined to contain interesting bioactivity. These extracts were subjected to various separation techniques, affording a number of bioactive compounds that were then characterized by spectral and degradative methods. A methanol extract of Cestrum latifolium Lam. yielded the known compound parissaponin Pb. Hydrolysis afforded its aglycone, the known spirostanol diosgenin. GCMS analysis characterized the derivatized, hydrolyzed sugars. Previous investigations of Albizia subdimidiata provided two saponins including the new compound albiziatrioside A. The sugar moieties of these two compounds required further characterization. They were characterized by spectral analysis of the partially hydrolyzed products and by GCMS analysis of the hydrolyzed sugars. Pittoviridoside, a saponin from Pittosporum viridiflorum, was isolated in a previous investigation. Further investigation was required to characterize the stereochemical environment of the sugar moiety. The stereochemistries of the pentose sugars were determined by conversion into thiazolidine acetates of known stereochemistries and analysis with standards by GCMS. Two new diterpenes were isolated from Hymenaea courbaril, which in an earlier investigation provided a new diterpene. The absolute configurations of these diterpenes were assigned on the basis of anisotropic NMR studies, X-ray crystallography, circular dichroism analysis and previously reported literature. A previous investigation of Miconia lepidota isolated two benzoquinones, primin and its n-heptyl analog. Fifteen analogs were synthesized for structure-activity relationship determination. It was found that benzoquinones with moderate-length alkyl side chains displayed the strongest activity in our yeast and cancer cell lines. / Ph. D.
24

Synthesis of an ingenane A/B-ring analogue : a model study for the total synthesis of ingenol /

Ross, Robert John January 1986 (has links)
No description available.
25

Natural Product Studies of Marine Organisms from the Western Atlantic

Unknown Date (has links)
The projects described in this dissertation are focused on compounds derived from marine organisms collected from the western Atlantic marine environment. Chapter 1 provides an introduction to the study of natural products chemistry, marine natural products, and overview of the research undertaken from natural product chemists. Chapter 2 describes the isolation and structure elucidation of a series of rare diterpenoids from the gorgonian Briareum asbestinum, together with their conformational analysis and biosynthetic interconversions. These rare diterpenes from Briareum asbestinum are linked by an unusual transannular oxa-6π electrocyclization which is described in detail and this work demonstates the biomimetic hemisynthesis of briareolate esters L (19) to B (22) achieved via an intermediary, briareolate ester G (2), through a controlled set of photoinduced isomerizations and a unique photochromic transannular oxa-6π electrocyclization. This work focuses largely on the mechanistic understanding of the photochemical production of these briarane diterpenoids and illustrates a unique UVA/UVC, photochromic switch which induces a transannular oxa- 6π electrocyclization. Chapter 3 describes the assay-guided isolation of marine antioxidants. This chapter focuses on the screening of marine organism extracts using the Ferric Reducing Antioxidant Power (FRAP) assay for antioxidant activity guided isolation of marine natural products. The chapter concludes with the activity guided isolation and structural elucidation of 1-O-palmitoyl-2-O-myristoyl-3-O-(6-sulfo-α-D-quinovopyranosyl)- glycerol (40) to show direct antioxidant potential through FRAP analysis. Chapter 4 describes the isolation, structural elucidation and pharmacological evaluation of the novel secondary metabolites iso-PsA(45), Iso-PsC (46), iso-PsD (47) as well as known Pseudopterosins A(41), B(42), C(43), D(44), K(48), K2’OAc(49), K2’OAc(50). These secondary metabolites were evaluated for both cytotoxicity. The chapter concludes with the screening of these compounds as αβ-amyloid fibril modulators utilizing atomic force microcopy (AFM). / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
26

Biosynthetic studies of fungal diterpene antibiotics /

Yao, Qingmei. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 150-161). Also available on the World Wide Web.
27

An asymmetric carbene cyclization cycloaddition strategy toward the synthesis of indicol

Lam, Sze-kui. January 2005 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.
28

Synthetic investigations on terpenoids

Selvakumar, N 07 1900 (has links)
The thesis entitled "Synthetic Investigations on Terpenoids" is divided into two sections. Section 1 deals with the total synthesis of sesquiterpenes belonging to the Zizsene group and Section 2 contains the synthetic investigations on the furanoid dlterpenes of labdane group.
29

Studies toward the synthesis of the kempane diterpene ring system, and some cascade radical cyclizations /

Bao, Guanglin, January 2000 (has links)
Thesis (Ph.D.)--Memorial University of Newfoundland, 2001. / Includes bibliographical references.
30

Synthesis of molecular probes for exploring the human consciousness, 5-HT₇ ligands and salvinorins /

Holmberg, Pär, January 2005 (has links)
Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 4 uppsatser.

Page generated in 0.0603 seconds