Browsing by Author "Lambert, D.W."

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    Palmatine and berberine chloride synergistically Inhibit NanH sialidase of Tannerella forsythia
    (Department of Microbiology, Nasarawa State University Keffi, 2022-05-05) Galleh, Raphael Peter; Lambert, D.W.; Stafford, G.P.
    The periodontal pathogen Tannerella forsythia is associated with severe periodontitis, and expresses NanH sialidases that cleave sialic acids by hydrolyzing the glycosidic bonds to underlying sugars. Palmatine and berberine chloride are plant-derived alkaloids with pharmacological effects, including anti-inflammatory and anti- bacterial properties. Recombinant NanH sialidase was purified using HisTag affinity chromatography while sialidase activity was determined using 4-methylumbelliferyl N-acetyl-a-D-neuraminic acid (MUNANA) as a substrate. The individual and synergistic effects of palmatine and berberine chloride on NanH sialidase inhibition was determined as well as their antimicrobial effects. The IC50 values of palmatine and berberine chloride were found to be 0.143 and 0.474 mM respectively. A significant synergistic effect was observed when a 0.20 mM:O.5O mM Palmatine:Berberine chloride mixture was used, inhibiting NanH sialidase by almost 1 00%, as compared to 0.2 mM palmatine and 0.5 mM berberine chloride invidually, which inhibit sialidase activityby 60.33 and 55.94%, respectively. Additionally, an antimicrobial viability assay was conducted and, 0.5 mM palmatine and 0.45 mM berberine showed a significant antimicrobial activity against Tannerella forsythia. Lastly, to examine potential toxicity to host cells, thecytotoxic effects of palmatine (0.1 5 mM) on H357 oral squamous carcinoma cells was investigated using a trypan blue assay and palmatine was found not to be toxic. In summary, a combination of palmatine and berberine display significant synergistic inhibitory effects on NanH with minimal cytotoxic effects as well as potential antimicrobialeffects on the oral pathogen T. forsythia. Suggesting thatthese compounds may have potential for future development.
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    Testing for novel inhibitors of periodontitis-associated sialidases
    (Department of Microbiology, Nasarawa State University Keffi, 2020-07-10) Galleh, Raphael Peter; Lambert, D.W.; Stafford, G.P.
    The microorganisms associated with severe periodontitis are the periodontal pathogens of the red complex: Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola. These organisms cleave sialic acids found at the terminal end of host glycoconjugates by hydrolysing the glycosidic linkages with their expressed sialidases, thereby affecting the integrity of the host periodontium and promoting disease progression. Both p. gingivalis (SiaPG) and T. forsythia (NanH) sialidase enzymes were purified using HisTag affinity chromatography and a range of putative synthetic and plant-based inhibitors were tested for their ability to inhibit both enzymes using a ٨لا٨لالا ٧ cleavage assay. Investigation of sialidase inhibitory activity of these compounds revealed that the plant derived alkaloids: Epicatechin gallate (IC50 = 21.75pM and 1 20.9pM) and Berberine chloride (IC50 = 106.2pM and 1 25.5pM) were more effective inhibitors of both SiaPg and NanH enzymes than the anti-influenza drug Zanamivir, an FDA approved viral neuraminidase inhibitor. Finally, a range of newly synthesized sialic acid analogues were effective in the micromolar to nanomolar range against both SiaPg and NanH enzymes with compound 2e3aDFNeu5Ac9N3 having an IC50 of (3.846pM and . ا م) respectively. The data suggests several novel inhibitors of these enzymes that might have future use as novel drugs against diseases such as periodontitis, and which we are currently testing further in host-pathogen interaction studies.