Inhibitory effects of Acacia extract on growth of blue-green algae Microcystis spp.

Effects of Acacia extract (AME) from Acacia decurrens Willdenow on growth of two species of cyanobacteria, Microcystis ichthyoblabe Kützing (M 95) and Microcystis aeruginosa (Kützing) Kützing (NEIS 298) were examined. AME showed an inhibitory effect on cyanobacterial growth in both species at 6 mg L -1, and induced negative growth at 12 mg L -1. On the contrary, there was no effect of AME on the growth of green alga, Chlamydomonas reinhardtii Dangeard (IAM C-9) even at 12 mg L -1. Analysis using silica gel thin-layer chromatography separated four bands, band 1-4, from the AME with a mobile phase solvent (1-Butanol: Acetic acid: H 2O=4:1:2 (v/v/v)), and band 2 induced the most inhibitory effect on both M. ichthyoblabe and M. aeruginosa growth. Liquid chromatography-mass spectrometry suggested that band 2 included gallic acid, epicatechin, and oligomer (dimer, trimer, tetramer and pentamer) catechins. These results suggested that the catechins were the main inhibitors in band 2 separated from AME on cyanobacerial growth. © The Plankton Society of Japan 2010.