Action of antialgal compounds fromJuncus effusus L. onSelenastrum capricornutum.

Twenty-nine free and glucosylated dihydrophenanthrenes and tetrahydropyrenes isolated fromJuncus effusus have been tested against the unicellular green algaSelenastrum capricornutum. The free compounds showed a strong inhibitory activity, while the glucosides were inactive or had a slight stimulating effect on growth. Tetrahydropyrene33, obtained by hydrolysis of the naturalβ-glucosides29 and30 or by hemisynthesis from1, is the most active compound, causing 90% inhibition of the growth at 2.5 × 10(-5) M concentration. Synthetic α-glucosides28, 31, and32 showed comparable activity to those of29 and30.