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 naturalß-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.

In vitro algal growth inhibition by phytotoxins ofTypha latifolia L.

The ether extract ofTypha latifolia L. inhibited the growth of some microalgae. Among the substances chromatographically isolated and characterized from the ether extract, three steroids [ß-sitosterol, (20S) 24-methylenlophenol, and stigmast-4-ene-3,6-dione] and three fatty acids [α- linolenic, linoleic, and an unidentified C8∶2] were found to inhibit the growth of some microalgae tested. A selective effect of these substance on blue-green algae (particularly on T 625Synechococcus leopoliensis and on T 1444Anabaena flosaquae) was observed.