A novel in vivo model to study bacterial pathogenesis and screen potential therapeutic targets.

As insects rely for their protection against infection on an entirely innate immune system, the use of an insect model is particularly relevant in the study of human newborn Escherichia coli K1 meningitis, the control of which has significant dependency on the innate immune system. Using an in vivo model of neuropathogenic E. coli meningitis, it is shown that immunization with E. coli K-12 can protect locusts against subsequent challenge of invasive E. coli K1. Immunization with other microbes such as Staphylococcus aureus and Acanthamoeba spp. had no effect on K1-induced locust mortality, suggesting immune specificity in invertebrates. The locust immune system was capable of memory and mounting protection against subsequent challenge with invasive K1 for up to 5 days. The usefulness of locusts for the assessment in vivo of potential therapeutic agents was tested. Gentamicin protected locusts against E. coli K1- and S. aureus-mediated death. These finding suggest that the simple locust model described in the present study has the scope in exploring the efficacy of novel drugs (testing large chemical libraries) in microbial diseases, allowing inexpensive, rapid, and even high-throughput experimentation and has no legislative restrictions. Future studies will determine bacterial antigenic determinants and how innate memory functions in locusts. A complete understanding of how locusts\u27 innate immune cells (i.e., haemocytes) respond robustly and specifically against bacterial pathogens will be crucial for the control of neonatal E. coli infection by limiting the ability of the bacteria to overwhelm the host immune system in the early stages of infection

Phytochemical and antibacterial studies on selected plant of the genus Hypericum

This thesis describes phytochemical studies on ten of the genes Hypericum and the evaluation of their antibacterial activity. Bio-assay guided fractionation using various chromatography techniques was used in this study. Eighteen compounds were isolated and their structures were characterised by extensive 1- and 2- dimensional NMR. Antibacterial includes Mycobacterium. bovis BCG (M bovis BCG), Mycobacterium. tuberculosis H37Rv (M tuberculosis)and panel of Staphylococcus aureus strains. Minimum inhibitory concentration (MIC) assay was used to evaluate antibacterial activity of the plant extract and isolated compounds. Enzymatic inhibition of ATP-dependent MurE ligase from M tuberculosis was assayed using a colorimetric phosphate detection method, mammalian microphage cell toxicity was also evaluated of interested isolated compounds. The investigation of H acmosepalum let isolation of eight compounds including β-sitosterol, hypercalin B and lupeol from hexane extract. Its chloroform extract gave hyperenone A, 1,7- dihydroxyxanthone and 2-Hydroxyxanthone. Catechin and epicatechin were isolated from methanol extract. Hyperenone A and hypercalin B exhibited antibacterial activity against multidrug-resistant strains of Staphylococcus aureus, with minimum inhibition concentration values ranging from 2-128 μg/ml, to 0.5-128 μg/ml., respectively. Hyperenone A showed growth inhibition against M tuberculosis H37Rv and M bovis BCG at 75 ug/ml. and 100 ug/ml., Neither hyperenone A nor hypercalin B inhibited the growth of Escherichia coli and were not toxic to cultured mammalian macrophage cells. Both compounds were tested for their ability to inhibit the A TP-dependent MurE ligase of M tuberculosis, a crucial enzyme in the cytoplasmic steps of peptidoglycan biosynthesis. Hyperenone A inhibited MurE selectively whereas hypercalin B did not have any effect on enzyme activity. Stigmasterol and tritrpenes were isolated from hexane extract of H patulum. Fractionation of methanol extract of this species afforded a series of flavanoid derivates including quercetin, rutin and flavanoid glycosides. All these isolated compounds were inactive against S. aureus at 256 μg/ml., Fractionation of methanol extract of H frondosum yielded mixture of catechin and epicatechin The hexane extract of the root of H olympicum led the isolation of two new tri-prylenated xanthones derivatives. These metabolites were active against S. aureus and MIC values ranged from 16-32 μg/ml. to 32-64 μg/ml. respectively. Chloroform extract led isolation of pentenoic acid.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Antibacterial sesquiterpenoid derivatives from Ferula ferulaeoides

Three new sesquiterpenoid derivatives 1, 2, and 3 were isolated from Ferula ferulaeoides. To confirm the structure, compound 2 was also synthesized via a condensation reaction between compound 1 and 2,2-dimethoxypropane. The structures of these three compounds were elucidated by means of spectroscopic and chemical methods. Their antibacterial activity against drug-resistant Staphylococcus aureus strains were evaluated with MIC values in the range of 0.5-128 µg/mL. Compounds 1 and 3 were capable of inhibiting efflux of ethidium bromide using an in vitro assay. The cytotoxicity of the compounds was evaluated on cultured HEK293 cells, and none of them showed toxicity to HEK293 cells at a concentration of 125 µg/mL

Four geranyl-bearing polyisoprenylated benzoylphloroglucinol derivatives from Hypericum sampsonii

Four new geranyl-bearing polyisoprenylated benzoylphloroglucinol derivatives, hypersampsone I (1), hypersampsone J (2), and hypersampsone K (3), together with hypersampsone L (4) which possessed a novel skeleton, were isolated from the fruit of Hypericum sampsonii. Their structures were determined on the basis of spectroscopic data, mainly 1D- and 2D-NMR spectroscopy and mass spectrometry. The structures of 1 and 2 were confirmed by X-ray crystallographic analysis

Norlignans, acylphloroglucinols, and a dimeric xanthone from Hypericum chinense

Two new norlignans, hyperiones A (1) and B (2), three new acylphloroglucinols, aspidinol C (3) and hyperaspidinols A (5) and B (6), the known compound aspidinol D (4), and the symmetrical dimeric xanthone hyperidixanthone (7) were isolated from Hypericum chinense. Their structures were established by spectroscopic analysis. In an antibacterial assay using a panel of multidrug-resistant (MDR) strains, compounds 3 and 4 exhibited promising activity against the NorA efflux protein overexpressing MDR Staphylococcus aureus strain SA-1199B with a minimum inhibitory concentration (MIC) of 2 ?g/mL (8.4 ?M) and 4 ?g/mL (16.8 ?M), respectively. The positive control antibiotic norfloxacin showed activity at MIC 32 ?g/mL (100 ?M)