Allelopathy Journal

The allelochemicals from terrestrial plants and macrophytes inhibited the cyanobacterial growth has been confirmed. Little information is available about the allelochemicals from biofilms, hence, we studied the extraction, isolation and identification of compounds from photoautotrophic biofilms. Ethyl acetate and ethanol extracted 34 compounds as compared to 14 compounds dichloromethane and water, showing that solvents with polarity index (4.4 to 5.1) were suitable extractants for extracting more allelochemicals from biofilms. Total of 16 known and 5 unknown compounds were isolated from the ethyl acetate extract of the biofilms, 8 known and 5 unknown compounds from methanol, 2 known and 3 unknown from dichloromethane, and 6 known and 3 unknown from water. The 3,4,5-trihydroxybenzoic acid extracted by methanol from biofilms was in highest quantity, besides it was also present in terrestrial plants and macrophytes, hence, was considered potential allelochemical on cyanobacterium. It significantly inhibited the growth of cyanobacterium Microcystis aeruginosa at 0.1 mg/L to 0.3 mg/L concentrations and the allelopathic effect increased with time. Another allelopathic compound ethyl-2-methylacetoacetate was also identified. It was concluded that some compounds extracted from biofilms were same to those extracted from terrestrial plants or macrophytes. However, the bioactivity of unidentified compounds extracted from biofilm should be determined on cyanobacterial growth.