Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Biochemistry

Background: Ý-Amyloid1-42, the major constituent of amyloid plaques, was believed to play a central role in the neuropathology of Alzheimer{u2019}s disease (AD) according to the{u2018}{u2018}amyloid cascade hypothesis. Hibiscus sabdariffa L. commonly named as " Roselle " is a member of malvaceae family.The aim of the present study was to investigate the effect of three colored calyces from Hibiscus sabdariffa L. on amyloid beta (AÝ42) production in a human neuroglioma model. Material and methods: The preparation of the three colored calyces extracts was performed within two solvent systems.The total flavonoid and the antioxidant activity by DPPH radical scavenging assay was evaluated.The in-vitro biological study was performed in a human neuroglioma cell line (H4) expressing the double Swedish mutation (K670N/M671L) of the human amyloid precursor protein (APPsw) under the transcriptional control of the hamster prion protein promoter. In addition to, Notch-mediated Hes1-Luciferase reporter assay was also investigated.The anti-COX activity and MTT assay were also evaluated. Results: All extracts showed a good inhibitory activity against DPPH free radical.The total flavonoid was detected in the present study as traces. No toxicity was detected by standard MTT assay against H4 cells treated with Roselle extracts. No inhibition activity was also observed against cyclooxygenases (COX-1 and COX- 2) by concentrations up to 600 ng/mL. All the different Roselle extracts allowed to inhibit AÝ42 levels in the neuroglioma cell line. Conclusion: The white green calyces at hot aqueous ethanol extraction was detected to be the best calyces and extraction method for alteration of AÝ42 in a human neuroglioma model via functional modulation of Þ-secretase mediated APP processing pathway

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