الفهرس 
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Abstract
Chemical investigation of Aspergillus niger’s metabolites (Trichocomaceae) Nature is considered a renewabe source for important pharmaceutical products. These natural products are derived from different sources as medicinal plants, marine organisms or microorganisms, etc…. Microorganisms are widely distributed on earth and include different organisms as bacteria, viruses and fungi. Their activities are ranging from varying from causing diseases to aiding in food processing and producing important chemicals and most enzymes. Endophytes are microorganisms that live in the internal tissues of their host without causing any apparent disease symptoms. They produce various secondary metabolites and provide several bioactive compounds currently used as pharmaceuticals. Marine endophytes play a vital role in survival of many marine stationary organisms and were reported to be the real producers of bioactive secondary metabolites that were isolated from the host macro-organism. Studies of marine endophytic organisms have increased in the last two decades and provide a sustainable, eco-friendly supply of various multipurpose bioactive compounds for pharmaceutical industry. Aspergillus niger is a promising fungus for the discovery of novel bioactive compounds, dating back one hundred years production of unique bioactive compounds. The isolated metabolites were found to be belonging to several chemical categories and showed versatile biological activities, viz., antitumor, antimicrobial, anti-inflammatory, antimalarial, and anti-oxidant. Therefore, the present study included two parts; the first one was devoted to isolation of pure fungi from the tunicate Phallusia nigra and its identification. Then, fermentation and cytotoxic activity screening of the highest yield fungal metabolite and finally, chemical investigation of secondary metabolites of Aspergillus niger ; an endophyte which was isolated from the inner surface of the tunicate Phallusia nigra. The second part for investigation of the physical properties and biological activities of some isolated compounds. Part I: Chemical investigation of Aspergillus niger isolated from the tunicate Phallusia nigra Chapter 1: Identification of pure isolated fungi, fermentation of the highest yield fungus and screening of its cytotoxic activity • Identification of fungi: Trichoderma longibrachiatum, Aspergillus ochraceus, Aspergillus terreus and Aspergillus sydowii were morphologically characterized at the Mycological Center, Faculty of Science, Assiut University, Egypt (pure cultures deposited with AUMC no. 13026, 13955, 13956, 13957, respectively). Aspergillus niger was identified by PCR using the universal fungal primers Internal Transcript Spacer regions (ITS1 and ITS4) (GenBank accession No.LC582533). • Culture medium optimization for the highest yield fungus: Each fungal strain was cultivated on PDA plates. The crude extract of each strain was weighed after dryness to yield 0.63, 0.54, 0.52 and 0.46 mg for Trichoderma longibrachiatum, Aspergillus ochraceus, Aspergillus terreus and Aspergillus sydowii, respectively while Aspergillus niger yielded 1.23 gm. So, the black‑colored fungus; Aspergillus niger; was chosen for the Culture medium optimization and the cytotoxic study. Aspergillus niger was cultivated on different solid cultures. The mat of each one was weighed yielding 0.5, 0.95 and 1.2 gm for rice, bran and wheat solid culture. So, wheat solid culture was chosen for large scale fermentation of Aspergillus niger. • MTT assay: Aspergillus niger extract showed the highest apoptotic activity on cultured HCT-116 cells with IC50 12.01±1.1. Also, it showed inhibitory activity on MCF-7 cells with IC50 15.53±1.2 and on HePG2 cells with IC50 26.33±1.8 as compared with doxorubicin. Thus A. niger is considered a candidate for promising anticancer drugs. Chapter 2: characterization of the isolated compounds The isolated compounds were identified using various spectroscopic techniques including; UV, IR, 1D-NMR and MS. Six naphtho--pyrones (2 monomers and 4 dimers) and one pyridine-4-one alkaloid were isolated and identified from the solid culture of marine-derived Aspergillus niger. Physical properties and biological investigation of some isolated compounds Chapter 1: Ability of some isolated compounds to synthesize silver nanoparticles (AgNPs) The synthesized AgNPs by compounds 3, 4 and 7 were well-dispersed, and their size was ranging from 8-30 nm in diameter. In addition, the morphology of the synthesized AgNPs was obviously spherical capped with the organic compounds which indicates a good stabilization effect of the investigated compounds. Chapter 2: Acetylcholine esterase inhibitory (AChEI) activity of some isolated comounds Inhibition of AChE has a major role in Alzheimer disease. Molecular docking simulation experiments were done for compounds 3, 4 and 7 and the results were compatible with AChE inhibitory assay results. Acetylcholine esterase inhibitory (AChEI) activity was assessed by using Ellman’s method. The results revealed that asperpyrone-type bis-naphtho-γ-pyrones showed remarkable AChE inhibition particularly with their green synthesized AgNPs. The AgNPs have increased the AChE inhibitory activity of compound 4 by 84 fold (IC50 value decreased from 7.52 to 0.089 µM) followed by Compound 3 AgNPs which its inhibitory activity has been increased by 16 fold (IC50 value decreased from 4.9 to 0.311 µM) compared to galanthamine as a positive control (IC50 values of 1.43). The activity of the alkaloid 7 also increased by 13 fold after AgNPs synthesis (IC50 value decreased from 20.17 to 1.53 µM). The linear naphtho-γ-pyrone 2 showed moderate inhibitory activity with IC50 value of 13.87 µM, while compound 1 didn’t show any inhibitory activity.