Impact of Cyanobacterium, Lyngbya semiplena on Antioxidant Status of a Tropical Teleost Oreochromis mossambicus (Peters)

Biological antioxidants are compounds that protect biological system against the harmful effect of free radicals. The acetone extracts of the cyanobacterium, Lyngbya semiplena isolated from Cochin estuary, was found to act as an effective antioxidant in the oxidation system of emulsified linoleic acid in vitro. Antioxidant properties were expressed in vivo also. When the cyanobacterium was incorporated in the feed of ethanol-exposed Oreochromis mossambicus, it could protect the fish from lipid peroxidation and from subsequent tissue damage. Lipid peroxidation was assessed in terms of malondialdehyde, hydroperoxides and conjugated dienes. Antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathiones -transferase and non-enzymic antioxidant substance, glutathione in various tissues were also determined. Higher levels of lipid peroxidation were observed in the animal tissues on exposure to ethanol. However, there was a decrease in ethanol accentuated lipid peroxidation on co-treatment with cyanobacterial feed. Experimental diets could effectively bring down the requirement of defensive antioxidant enzymes in various tissues indicating that cyanobacteria could act as an antioxidant by scavenging the free radicals produced during ethanol exposure. Lyngbya semiplena is a food grade organism, highly nutritious and readily available from natural waters. These properties render it attractive for use in fish feed.