الفهرس 
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Abstract
1-Seaweeds (marine acroalgae) are primitive,phytosynthetic organisms live in sea or in brackish water. They are classified on the basis of their pigment constituents into red algae (Rhodophyceae), brown algae (phaeophycceae) and green algae (chlorophyceae).Red and brown algae are almost exclusively marine, The seaweeds have been utilized mainly as raw material or its extracts that used in the pharmaceutical, cosmetic and food industries .Furthermore, they are used for human and animal nutrition as feed or as fertilizers and soil conditioner.
2- Five species of seaweeds were collected from Rocky Bay of Abu Qir (31º 20’ N and 30º 29’ E). All samples were brought to laboratory in plastic bags containing sea water to revent evaporation. The collected seaweeds were cleaned, then washed with fresh water to remove surface salts. The collected species are the following: Ulva lactuca, Ulva fasciata, Enteromorpha intestinalis, Jania rubens, and gelidum spinosum.
3- Different solvents (acetone, chloroform, ethylacetate, ethanol, hexan and methanol) were used to determine the best organic solvents for extraction of the antimicrobial agent .Chloroform extracts of Ulva lactuca and Ulva fasciata showed the strongest inhibitory effect on the tested Bacterial (K. pneumoniae and P. mirabilis) and Fungl species (A. flavus, A.fumingatus and A. niger ) relative to other solvents.
4- Seaweeds possess antioxidant potential which could be considerd long future applications. chloroform extracts of the seaweeds were assessed for their antioxidant activity using DPPH (2,2 Diphenyl picryl hydrazyl) radical scavenging activity and antioxidant using phosphomolybdate assay, among the species Ulva lactuca and Ulva fasciata demonstrated greater antioxidant potential. During DPPH free radical scavenging activity, the IC50 of the extract was found to be 6.32±0.29 mg/ml for Ulva lactuca and 6.61±0.27 mg/ml for Ulva fasciata. Radical scavenging activity by phosphomolybdate assay was 2.13% for Ulva lactuca and 1.51% for Ulva fasciata.
5- The anticancer activity of collected seaweeds were evaluated against cancer cell line namely Hepatocellular carcinoma (HEPG-2), Mammary gland (MCF-7), Epithelioid carcinoma (Hela) and human prosta cancer (pc-3) by the MTT assay .The highest cytotoxic activity was displayed by Ulva lactuca chloroform extract against MCF-7 followed by Ulva fasciata chloroform extract against HepG2 and pc3 and weak inhibitory activity was also demonstrated by Gelidium spinosum.
6- Ulva lactuca and Ulva fasciata extracts were fractionated using G EDWC; 60-200 colum chromatography eluted with gradients of mobile phase from 3:7% methanol: chloroform to 7:3% methanol: chloroform. Twenty one fractions were collected of which only five fractions showed antimicrobial activities against bacteria as well as fungi.
7- Different chemical analysis techniques were carried out to determine the chemical structure of the active compound of the chloroform Ulva lactuca and Ulva fasciata extracts
.FTIR analysis was indicated the prescence of CH aliphatic (CH,CH2 and CH3), C=O, C=C, C-O, aromatic phenyl ring (CH, CH2 and CH3) chemical groups. The gas chromatography mass spectrometry (GC-MS) was also
used for Ulva lactuca antibacterial extract and revealed its high content of phenolic compounds, the results indicated the presence of 4 peaks with different retention times and peak relative intensities, All peak areas of the chromatogram were relatively small except the parent peak at retention time of 35.436 min. which was corresponding to 100% relative intensity and was identified according to its molecular mass to be di-isooctyl phthalate (Di-(2-ethylhexyl)-phthalate DEHP) for Ulva lactuca and Butylated hydroxy toluene for Ulva fasciata. The molecular formula of this active compound was C24H38o4, molecular weight of 390.56 and density of 0.983 g/ml for diisooctylphthalate and C16H26O3, molecular weight of 220.356and density of 1.048 g/ml