الفهرس 
Brown algae definitionOnly 14 pages are availabe for public view
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Abstract
Brown algae (BA) belong to the group Heterokontophyta, a large group of eukaryotic organisms distinguished most prominently by having chloroplasts surrounded by four membranes, suggesting an origin from a symbiotic relationship between a basal eukaryote and another eukaryotic organism. Most BA contain the pigment fucoxanthin, which is responsible for the distinctive greenish-brown color that gives them their name. Brown algae are unique among heterokonts in developing into multicellular forms with differentiated tissues, but they reproduce by means of flagellated spores and gametes that closely resemble cells of other heterokonts. Genetic studies show their closest relatives to be the yellow-green algae. . Worldwide, over 1500–2000 species of BA are known. Some species are important in commercial use because they have become subjects of extensive research in their own right. They have environmental importance too through carbon fixation.
In Egypt, BA are also frequently encountered as the major vegetation in shallow water tropical and subtropical habitats, even though herbivorous predators are plentiful. Hence, the correlation between secondary metabolite synthesis within this family and predator avoidance seems to be pronounced . In the littoral zone of the Egyptian coast, BA are currently the most dominant group. Members of Sargassum genus represent valuable sources of a wide spectrum of complex lipids, essential fatty acids and amino acids. Sargassum subrepandum (Forsk) C. Ag. is quite common in the Egyptian Red Sea coast , Brown algae consist mainly of water (90 percent) in the native state. Polysaccharides are major components and comprise alginates, cellulose, and sulfated polysaccharides such as fucoidans and laminarins. Other components include proteins, free mannitol, minerals such as iodine and arsenic (inorganic and organic), polyphenols, peptides, fatty compounds, and various pigments. Alginates, probably the most widely used of the algal extracts, are composed of block copolymers of mannuronic and guluronic acid sugars and have been adopted by the food industry as thickening agents and by the pharmaceutical industry as binders, gelling agents, and wound absorbents.
Obesity is defined as an excessive accumulation of body fat mass to the extent that individual’s health will be negatively affected. Indeed, obesity is considered as a top risk factor to develop deleterious associated pathologies as liver and coronary heart diseases, osteoarthritis and asthma, and a combination of medical disorders which includes: type 2 diabetes, high blood pressure, high blood cholesterol, and high triglyceride levels.The prevalence of obesity over the past years has been in constant progression leading the World Health Organization (WHO) to consider it as an epidemic pathology and one of the leading preventable causes of death worldwide.
Oxidative stress (OS) was initially defined by Sies (1985) as a serious imbalance between oxidation and antioxidants, “a disturbance in the prooxidant–antioxidant balance in favor of the former, leading to potential damage”. So, it reflects an imbalance between the systemic manifestation of reactive oxygen species (ROS) and a biological system’s ability to readily detoxify the reactive intermediates or to repair the resulting damage. Disturbances in the normal redox state of cells can cause toxic effects through the production of peroxides and free radicals that damage all components of the cell, including proteins, lipids, and DNA. Oxidative stress from oxidative metabolism causes base damage, as well as strand breaks in DNA. In humans