Growth Inhibition of Fresh-water Algae and Duckweed by Falcarindiol Isolated from Flexuous Bittercress (Cardamine flexuosa With)

During the search for natural algicidal compound, we found that the methanol extract of flexuous bittercress (Cardamine flexuosa With) inhibited strongly the growth of Microcystis aeruginosa. An algicidal compound (30 mg) was isolated from the methanol extract through ethylacetate partition, silica gel column and Sephadex LH-20 column chromatography. It's chemical structure was determined to be falcarindiol (Z-heptadeca-1,9-diene-4,6-diyne-3R,8S-diol) by mass and NMR spectral data. Falcarindiol showed a dose-dependent response to blue-green alga M. aeruginosa and green alga Chlorella vulgaris in a range of 0.25 to 10 μg mL-1. The IC50 of falcarinol to M. aeruginosa and C. vulgaris was 0.19 and 3.13 μg mL-1, respectively. It showed much lower algicidal activity to C. vulgaris compared with M. aeruginosa. On the other hand, the compound inhibited a growth of duckweed (Lemna pausicostata) with IC50 value of 6.17 μg mL-1. As a results, falcarindiol appears to have a strong potential for preventing the blooming of bule-green algae such as Microcystis spp. in pond or for the environmentally friendly control of microalgae and weeds that are harmful to water-logged rice.