Biochemical composition, biological activities and toxicological effects of two non-nodularin producing strains of Nodularia spumigena Mertens in Jürgens

Abstract

We tested two non-nodularin-producing strains of the cyanobacterium Nodularia spumigena, isolated from a marine (Kachelotplate) and a brackish water (Banter Sea, Wilhelmshaven) habitat in Lower Saxony, Germany, for allelochemical production (e.g. alkaloids, flavonoids) and allelopathic activities (e.g. algicidal, anti-microbial). The growth experiments showed for the marine strain the highest cell density at 10 and 20 °C for the brackish water isolate (80 μmol photons m−2 s−1). Phytochemical screening of the biomass extracts gave positive results for alkaloids, flavonoids, sterols and terpenoids in some of the tested assays. Most of these compounds were not present in supernatant extracts. Besides proalgal and anti-cyanobacterial properties of the high temperature treated marine strain, the supernatant extracts showed profungal and antibacterial activities in the 20 °C treated assays. In both, supernatant and biomass extracts, significant anti-oxidative activities were observed in the high-irradiance-treated marine and brackish water isolates. The highest toxicity was observed at the 5 and 20 °C brackish water isolates as well as 5 °C treated marine strain. With regard to fatty acid composition, both strains showed high levels of polyunsaturated fatty acids (PUFAs) and saturated fatty acids, with values of 36–54 % and 11–29 % of total fatty acids, respectively, whereas the levels of monounsaturated fatty acids were in general lower (8–16 %). Among PUFAs, linoleic (C18:2), α-linoleic (C18:3), γ-linoleic (C18:3) and arachidonic acid (C20:4) accounted 36.2 % of the total polyunsaturated fatty acids in the brackish water strain, while in the marine isolate, it was only 10.6 %.