Action of antialgal compounds from Juncus effusus L. on Selenastrum capricornutum

Twenty-nine free and glucosylated dihydrophenanthrenes and tetrahydropyrenes isolated from Juncus effusus have been tested against the unicellular green alga Selenastrum capricornutum. The free compounds showed a strong inhibitory activity, while the glucosides were inactive or had a slight stimulating effect on growth. Tetrahydropyrene 33, obtained by hydrolysis of the natural β-glucosides 29 and 30 or by hemisynthesis from 1, is the most active compound, causing 90% inhibition of the growth at 2.5 × 10-5 M concentration. Synthetic α-glucosides 28, 31, and 32 showed comparable activity to those of 29 and 30. © 1996 Plenum Publishing Corporation.