In vitro antioxidant properties of edible marine algae Sargassum swartzii, Ulva fasciata and Chaetomorpha antennina of Kerala coast

Oxidative stress induced by the free radicals has been gained a vital importance as it forms the root cause of about 200 human diseases [1]. Free radicals are highly reactive molecules with unpaired electrons and are produced during various cellular processes [2]. They represent an essential part of metabolism and aerobic life. Many of the reactive oxygen species (ROS) and reactive nitrogen species (RNS) are grouped under free radicals. These include superoxide anions (O2.), hydroxyl radical (.OH), singlet oxygen, hydrogen peroxide (H2O2), ferric ion, nitric oxide (NO) and so on [3]. ROS and RNS are produced from both endogenous (inflammation, mental stressand cancer) and exogenous (pollutants, drugs and radiations) sources [4]. Under normal conditions ROS participate in many physiological functions such as protecting body from invading pathogens, regulates calcium concentration and act as second messengers [5]. They participate in the signal transduction of cytokine and tyrosine receptor, serine/threonine kinases and G proteincoupled receptors [3]. They are also essential in development and differentiation process [6]. Several degenerative changes in the cells and tissues due to oxidative stress can lead to many deadly diseases [7]. The oxidative stress damages nucleic acids, lipids and proteins in our body, alters cellular functions and finally results in apoptosis or necrosis [5]. Also it is responsible for the progression of diseases like diabetics, rheumatoid arthritis, myocardial infarction, cancer, post-ischemic perfusion injury, autoimmune pathologies, cardiovascular, neurodegenerative and inflammatory diseases [8]. Antioxidants can grant protection from oxidative damages and prevent the onset of many chronic diseases [9]. They are naturally present in our body (endogenous) and the additional supplementation can be done through the diet (exogenous). Natural antioxidants like ascorbic acid (vitamin C), α-tocopherol, and carotenoids are readily absorbed through diet [10]. Butyl hydroxyanisole (BHA) and butyl hydroxytoluene (BHT) are synthetic antioxidants but are proven to cause major side effects such as cancer [11]. The current trends in the pharmaceutical industries are the exploration of natural antioxidants to resolve such issues. Plants have been widely investigated as the potent source of Oxidative stress is reported to be the main cause of various life style diseases. This stress is due to the imbalance of oxidants and anti oxidants. Seaweeds form the richest renewable source of ample bioactive compounds that promote them as a vital candidate in therapeutics, especially for drug development. Among the seaweed born macromolecules, the sulfated polysaccharides from brown, green and red algae were reported to have antioxidant activities, despite of their structural and nutritional significance. In the current study, the sulfated polysaccharides were isolated from three marine algae, Sargassum swartzii, Ulva fasciata and Chaetomorpha antennina. The carbohydrate content in the three edible algae was found to be 12.9%, 12.3% and 12.7% respectively. Of the three, Sargassum swartzii contains high sulfate content, which might be responsible for its better bioactivity. The antioxidant capability of the polysaccharides was determined by using standard in vitro assays and was found to be good in scavenging hydrogen peroxide. However, the total antioxidant activity and reducing power were less effective. Among the three, Sargassum swartzii showed superior activity and can be a good candidate for antioxidant therapies.