الفهرس 
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Abstract
Biodiversity and biological genetic wealth are considered together one of the most important natural resources. Wise and cost-effective utilization of such resources needs careful investigation before implementation. This helps greatly in adopting viable environmental policy. The present work has been designed for the purpose of carefully investigating the pharmaceutical potential of an Egyptian cyanobacterium species Arthrospira fusiformis inhabiting lake Maryut south west of Alexandria city.
Natural products have long been used as food additives, fragrances, pigments, insecticides, drugs, etc. Until 1989, about 25% of all pharmaceutical sales were drugs derived from plant natural products and an additional 12% were based on microbial produced natural products’’*. Only recently aquatic organisms have gained attention in that respect.
The aquatic environment contains over 80% of the world’s plant and animal species’2’, and is thus an exceptional reservoir of bioactive natural products, many of which exhibit structural/chemical features which are not found in terrestrial natural products’3*.
This diversity offers unique chemical compounds with the potential for industrial development such as pharmaceuticals, cosmetics, nutritional supplements, molecular probes, fine chemicals and agrochemicals’4*. As an example 10 000 new metabolites have been recently isolated from aquatic organisms, many of which are endowed with pharmacodynamic properties’4*.
In the past 50 years more than 14,000 natural products derived from aquatic organisms attracted the interest of pharmaceutical companies for their widespread applications’5*, 25 % of which were from algae’6*. Back in the 1950s, Bergmann et al. isolated several nucleosides from the Caribbean sponge Tethya crypta, two of which contained a rare sugar arabinose rather than ribose. This discovery led researchers to synthesize nucleoside analogues, which improved antiviral activity’7, *.
The use of algae for therapeutic purposes and the systematic examination of algae for biologically active substances, began in the 1950’s’9*. In the 1970’s the Roche Research Institute of Marine Pharmacology (PRIMP) in Australia focused research to emphasize in vivo examination of biologically active compounds extracted from aquatic organisms and they pioneered the screening of crude extracts rather than pure compounds”0*.
Blue-green algae or cyanobacteria are worth screening for new biologically active secondary metabolites, as they can be cultured in the laboratory with relative ease to provide a consistent source of bioactive compounds’1 ’*.
Although cyanobacteria are very rich in bioactive and toxic compounds, which can be extracted, purified and used in drug design, they are known to be toxic organisms. The only non-toxic cyanobacteria, known until now, is Arthrospira. Arthrospira is well known since ancient time as food additive and animal feed’11*. It is rich in vitamins, minerals, proteins and fatty acids’12’13’14*, activating immune response’15,16* and producing anticarcinogenic’17, 8* as well as antiviral polysaccharides’18,19* inhibiting the infection for herpes simplex virus type 1 and type 2, pseudorabies virus, human cytomegalovirus’20* as well as measles virus, mumps virus, influenza A virus’21* and HIV-l’21,22*, producing allophycocyanin, which inhibits enterovirus-71’23*. Arthrospira was also found to excrete exo-polysaccharides (Spirulan-like substances) with antiviral effect’24’26*. The highest effective antiviral compound purified from Arthrospira was found to be Ca-Spirulan, a sulphated polysaccharide attached to Calcium ions, which is extracted after 1 hour of boiling the cyanobacterium’20,27*.