Chemical Screening for Bioactive Substances in Culture Media of Microalgae and Cyanobacteria from Marine and Brackish Water Habitats: First Results

Abstract

Culture media of 24 commonly occurring microalgal and cyanobacteria species were subjected to a screening for total alkaloids, saponins, and phenol compounds, especially flavonoids and tannins. Both Wagner's and Mayer's reagents were employed in the alkaloid screening. Ferric chloride solution was used to detect phenolic compounds. Tannins were identified by the gelatine-salt block test. Shinoda's color reaction was used for flavonoids. Saponins were detected by the froth method. The species investigated were isolated from different marine and brackish water habitats. Media of five species gave positive alkaloid reactions with both reagents, whereas those of seven others were reactive only in one test. For the remaining 23 species, the presence of alkaloids in the culture medium can be excluded. In the media of 16 species, phenolic compounds were present. Five species produced ferric chloride–positive phenolic compounds. In six cases, positive gelatine-salt block tests were recorded. Four media gave positive reactions to the flavonoid test. It can therefore be assumed that at least two species excreted phenolic compounds other than flavonoids or tannins. Two media gave a positive saponin test.