In 1962, Owen, Dietz, and Camiener reported the isolation of a new antitumor antibiotic from the culture filtrate of Streptomyces sparsogenes. The structure of the crystalline antibiotic, named sparsomycin, remained elusive until 1970, when Wiley and MacKellar reported results of spectroscopic and degradation studies which elucidated the structure. In addition to the molecular structure, investigators have examined the mechanism of action, toxicity, and related analogues, striving to establish sparsomycin or a synthetic analogue's usefulness as an effective chemotherapeutic agent. The initial pharmacological evaluation of sparsomycin revealed it possessed activity against KB human epidermoid carcinoma cells, a variety of gram-negative and gram-positive bacteria, and fungi. This broad spectrum of activity prompted a closer examination of the biochemical mechanisms. These studies revealed sparsomycin interfered with protein synthesis by inhibiting peptide bond formation near the enzyme peptidyl transferase. Ottenheijm, Liskamp, and Tijhuis reported the first total synthesis of sparsomycin in 1979, which provided access to greater quantities of the material for investigational use. Sparsomycin was selected for use by cancer patients in phase I clinical trials, but was found to cause ocular toxicity which hindered its development as an antitumor agent. In an effort to reduce or eradicate the toxic effects while maintaining the antitumor activity, analogues of sparsomycin were prepared. Using the sparsomycin analogues which were synthesized, studies were performed to determine the effect alteration of key structural parameters had on the efficacy of the compounds. Previous investigators examined analogues which incorporated modifications of the uracil ring, the unique mono-oxodithioacetal moiety, and the stereochemical configuration of the chiral centers. Vince and Lee reported there was an apparent requirement for the Q-configuration at the asymmetric carbon atom. Overall, however, the small number of sparsomycin analogues prepared and evaluated limited the definitive statements concerning the functional groups required for antitumor activity. In order to expand and clarify the structure-activity relationships, three series of new sparsomycin analogues were prepared for this project. The compounds of Series I and II, distinguished by the inclusion or exclusion of a hydroxymethyl functional group, were designed to elucidate the effect on activity of replacing the mono-oxodithioacetal side chain of sparsomycin with 4-substituted benzyl groups. The Series III analogues, which excluded the hydroxymethyl functional group, featured a 4-substituted benzyl amide group in place of the mono-oxodithioacetal moiety of sparsomycin, and were designed to investigate the potential interaction of an amide oxygen in contrast to the sulfoxide oxygen of sparsomycin. The target compounds synthesized for this project were experimentally examined to quantitate their effects on [75Se]-selenomethionine incorporation as an 125 cell growth, indirect measurement of protein synthesis, and 5-125I-iodo- 2-deoxyuridine incorporation as an indirect measurement of DNA synthesis in bone marrow, P388 lymphocytic leukemia, and P815 mastocytoma cells. The results for the Series I and II analogues indicated the removal of the hydroxymethyl functional group as seen in sparsomycin affected activity to varying degrees depending upon the assay and the type of cells used. The results for the Series III compounds suggested the removal of the hydroxymethyl functional group and substitution of the mono-oxodithioacetal side chain of sparsomycin with a substituted benzyl amide moiety was not beneficial for activity. Finally, examination of the collective data revealed that the bromobenzyl-substituted analogues consistently imparted the greatest inhibitory activity, while the methoxybenzyl-substituted analogues displayed the least. The methyflnnzyl and the unsubstituted benzyl compounds were intermediate in inhibitory potency. The activity may correspond to the lipophilic and electronic characteristics of the substituents on the benzyl moiety of the analogues. It appears that the bromobenzyl-substituent of hydrophobic and electron withdrawing character is optimal for inhibitory activity, and conversely, the methoxybenzyl substituent of hydrophilic and electron donating character is least desirable.

Human immunodeficiency virus (HIV) and opioid abuse have been described as synergistic epidemics. Pharmacologically, it has been found that opioids have the capacity to enhance HIV infection and replication. Research has shown that activation of the mu-opioid receptor (MOR) elevates the expression of the HIV-1 entry co-receptor CXCR4 on T-lymphocytes in the peripheral nervous system, thus allowing for enhanced viral entry and invasion. Although the exact mechanism for opioid modulation of CXCR4 expression and subsequent exacerbation of HIV is unknown, several hypotheses exist. One hypothesis is that MOR and CXCR4 are functionally interacting through the formation of a heterodimer. This hypothesis is supported by studies substantiating the ability for MOR and CXCR4 to form heterodimers with other GPCRs, and the finding that MOR and CXCR4 were co-expressed in several central and peripheral regions including immune cells. To test this hypothesis, a series of bivalent ligands containing both a mu opioid receptor (MOR) antagonist and a CXCR4 antagonist pharmacophore was designed and synthesized to understand the pharmacological role of the putative CXCR4-MOR heterodimer in opioid exacerbated HIV progression. These bivalent ligands were evaluated for their binding and functional activities in radioligand binding, antibody binding, [35S]GTPγS, and calcium mobilization assays. In these assays, the bivalent ligands were shown to maintain binding and functional activities in both MOR and CXCR4 monoclonal cell lines. In addition, these bivalent ligands were evaluated for their ability to block HIV entry in a reverse transcriptase assay, and for their ability to inhibit morphine exacerbated HIV invasion in an LTR-luciferase assay. In these assays, the bivalent ligands were shown to inhibit HIV entry in a dose dependent manner. However, due to experimental limitations in our morphine exacerbated reporter system, the ability for the bivalent ligands to inhibit viral entry upon morphine co-exposure was not fully validated. Finally, molecular modeling approaches were utilized to visualize the putative binding modes of the bivalent ligands in a constructed MOR-CXCR4 heterodimer model. Overall, these studies have provided a solid basis for the utility of bivalent ligands in studying MOR-CXCR4 interactions and their involvement in opioid potentiated HIV progression. Further studies are ongoing to optimize the bivalent ligands construct and explore new analyses to evaluate their ability to block opioid modulation of the virus.

published_or_final_version / Paediatrics and Adolescent Medicine / Master / Master of Philosophy

Traditional medicine is very popular in the United Arab Emirates. The present study is part of an active programme directed towards phytochemical, pharmacological and toxicological studies on herbs used in folkloric medicine. Leucas inflata Benth, Salvia aegyptiaca L. and Teucrium stocksianum Boiss belonging to the family Labiatae were selected for this study. The coarsly powdered plant materials were extracted and the dried extracts were fractionated using different chromatographic procedures. The structures of the isolated compounds were elucidated using spectroscopic and spectrometric techniques. The acetone extract of L. inflata afforded stigmasterol, the 3ß-glucoside of sitosterola nd a chromone( leucasone[ 2,8-dimethyl-(2,2-dimethylethenyl)-5,6-benzo-4 pyrone]). Also a number of coumarins were obtained: coumarsabin [4,7 dimethoxy-3,5 dimethylcoumarin], 8-methoxycoumarsabin[4 ,7,8 trimethoxy-3,5-dimethylcoumarin], siderin [4,7-dimethoxy-5-methyl coumarin] and coumarleucasin [5-formyl-4,7,8- trimethoxy-3-methylc oumarin].L eucasonea ndc oumarleucasina re novel compounds. The acetone extract of S. aegyptiaca afforded oleanolic acid (3ß-hydroxy-olean- 12-en-28-oic acid), 3ß-hydroxy-oleana-11,13(18)-dien-28-oic acid, the 3ß-glucoside of sitosterol, ß-sitosterol and stigmasterol. Three novel diterpenoids were isolated (6- methyl-cryptoacetalide; epi-6-methyl-cryptoacetalide and 6-methylcryptotanshinone (14,16-epoxy-6-methyl-5(10), 6,8,13-abietatetraene-11,12-dione). In addition, the flavonoids 5-hydroxy-7,3', 4'-trimethoxyflavone and 5,6-dihydroxy-7,3', 4'-trimethoxyflavone were isolated. A number of compounds were isolated from the n -hexane extract of T. stocksianum: 5-hydroxy-7,4'-dimethoxyflavone, salvigenin (5- hydroxy-6,7,4'- trimethoxyflavone), oleanolic acid (3, ß-hydroxy-olean-12-en-28-oic acid) and two diastereoisomeric sesquiterpenoids shiromool 1,10-epoxide (1ß, 10a; 4 ß, 5a-diepoxy-7a- H-germacran-6ß -ol) and shiromool 1,10-epoxide (1 a, 10 ß; 4 ß, 5 a -diepoxy-7a -Hgermacran- 6ß-ol). This is the first report of the two diastereoisomers as natural products, although the latter was previously produced as a synthetic product. The essential oils obtained by steam distillation of the aerial parts of T. stocksianum and S. aegyptiaca were analysed by GC and GC/MS. Forty-one components were identified in the oil samples of T. stocksianum. The major compounds were alpha-cadinol and delta-cadinene. S. aegyptiaca oil afforded twenty-six components and the most predominant constituents were beta-caryophyllene and gammamuurolene. The pharmacological studies of the methanol and acetone extracts of L. inflata on mice showed that they significantly and dose - dependently, reduced formalininduced pain, acetic acid -induced abdominal constrictions and increased the reaction time in the hot-plate test. Both extracts caused significant and dose-related impairment in the sensorimotor control of treated mice. Both extracts exhibited anti-inflammatory action by reducing paw edema of treated mice. The extracts did not significantly affect the rectal temperature of normothermic mice. However, they were effective in preventing Brewers yeast -induced pyrexia. It is concluded that the crude methanol and acetone extract of L. inflata has CNS depressant properties, manifested as antinociception and sedation. Both extracts have anti-inflammatory and antipyretic actions. The crude acetone and methanol extracts of S. aegyptiaca caused dose-related inhibition of acetic acid-induced abdominal constriction, and significantly reduced formalin-induced pain. Treatment with the extracts significantly increased the reaction time in the hot-plate test. In treated mice both extracts caused significant and doserelated impairment of the sensorimotor control. Treatment with both extracts did not significantly affect the rectal temperature of normothermic mice. The methanol extract (0.5 and 1.0 g/ Kg) did not affect the rectal temperature of hyperthermic mice, but the acetone extract was effective in significantly reducing the rectal temperature of hyperthermic mice. It is concluded that the crude methanol and acetone extract of S. aegyptiaca has CNS depressant properties, manifested as antinociception and sedation. Both extracts have some anti-inflammatory and antipyretic actions. Generally the acetone extract appeared to be slightly more effective than the methanol extract in this regard.

published_or_final_version / Physiology / Master / Master of Philosophy

No description available.

No description available.

Thesis (M.Sc.)(Plant Science))--University of Pretoria, 2007. / Includes bibliographical references.

Thesis (Ph.D.)--University of Florida, 2009. / Title from title page of source document. Document formatted into pages; contains 335 pages. Includes vita. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 1996. / Includes bibliographical references (leaves 72-88).