Potential of Benthic Diatoms Achnanthes longipes, Amphora coffeaeformisand Navicula sp. (Bacillariophyceae) as Antioxidant Sources

Reactive oxygen species (ROS) such as hydrogen peroxide, hydroxyl radicals and superoxide anions, which are produced because of exogenous factors (tobacco smoke, ionizing radiation and certain pollutants) and endogenous factors (normal aerobic respiration) have been implicated in cellular processes such as mutagenesis, carcinogenesis and premature aging. ROS have the ability to react with a large variety of easily oxidisable cellular components, such as proteins, lipids and lipoproteins (Fridovich 1995). Oxidation is one of the major reasons of food deterioration, resulting to the destruction of fat-soluble vitamins and development of off colors and toxicants (Yang et al. 2000; Ukeda et al. 2002). Besides, in the food industry lipid peroxidation is an important deteriorative reaction during processing and storage. Commercial antioxidant supplements such as butylated hydroxyl anisole (BHA), butylated hydroxy tolouene (BHT), α-tocopherol and propyl gallate (PG) have been used in order to reduce oxidative damages in human body (Sherwin 1990; Gulcin et al. 2002). However, it is suspected that those antioxidants are responsible for some side effects such as liver damage and carcinogenesis. Antioxidants are involved with the oxidation mechanism by scavenging free radicals, chelating catalytic metals and by acting as oxygen scavengers (Shahidi and Wanasundara 1992; Buyukokuroglu et al. 2001). As a natural antioxidant source, plants have an ability to absorb the sun’s radiation for generating high levels of oxygen as secondary metabolites of photosynthesis. Oxygen is easily activated by ultra violet (UV) radiation and heat from the sunlight to produce toxic ROS. Therefore, plants produce various antioxidative comAlgae Volume 24(1): 47-55, 2009