Inducement of antioxidant production of Spirulina platensis and the investigation of its hepatoprotective effect

In this study, we aimed to increase the amount of bioactive molecules with antioxidant activity in Spirulina platensis as a response to oxidative stress by a two-step batch mode cultivation and evaluate the hepatoprotective effect of S. platensis cultures grown by this way. Light intensity was used as an environmental inducer in antioxidant production. The investigation of the effect of the sudden shift from low light to high light intensity on phenolic compound production, antioxidant activity, growth, and biomass composition of S. platensis was undertaken. It was found that total amounts of carbohydrate, phycocyanin, carotenoid, malondialdehyde and antioxidant activities were significantly increased while total protein amounts were decreased (p<0,05) correspondingly to the increased light intensity.The amount of phenolic compounds which are regarded as important seconder metabolites with various biological activities was significantly increased by approximately eightfold (p<0,01). The relationships between antioxidant activities and total amounts of phenolic compounds were significantly correlated at the 99% confidence level (p<0,01) indicating that phenolic compounds were major contributors of antioxidant activities. It was observed histologically that S. platensis biomass with increased antioxidant activity had more hepatoprotective effect against CCl4 induced acute liver injury. These results suggest that S. platensis with enhanced antioxidant activity could be a safe alternative to synthethic antioxidants and also potential candidate source of therapeutic agent for diseases induced by free radicals.Key words: S. platensis, antioxidant activity, phenolic compounds, liver