Antialgal Compositions from Potamogeton maackianus by Activity-Guided Fractionation

Hexane extracts of Potamogeton maackianus were fractionated using silica gel column chromatography under room pressure by antialgal activity-guidence. Ten fractions were obtained and three of them shown obvious antialgal activities. These three active fractions were further separated using gel chromatography (Sephadex LH-20). Then the active fractions Fr 3-5, 3-7 and 3-8 were obtained and their percentage inhibition of algal growth rates were up to 66, 47.4 and 66.7% respectively at the concentration of 15mg/L, more than the 30.8% algal growth inhibition rate of Fr 3 at 20mg/L. The algal growth inhibition rate of Fr 4-3, up to 78.8% at 15mg/L, was higher than that of Fr4 (only 30.7%). Fr6-1, 6-3 and 6-4 were shown much higher antialgal activities than Fr6 though further separation, especially Fr 6-3 and 6-4 whose algal growth inhibition rates reached 74.7 and 89.6%. The chemical components of active Fr 3, 4 and 6 were also analysis through GC-MS. The results indicated that Phytol and 1,1-cyclohexanedimethanol were the most abundant compounds in Fr 3 and hexadecanoic acid, campesterol, stigmasterol and sitosterol were the main components of Fr 4. As for Fr 6, the concentration of hexadecanoic acid was higher than other components although there are 16 compounds existed in the Fr 6. These bioassay results indicated that hexane extracts and some of their separated fractions showed the obvious inhibitory activity on growth of algae. The components in extracts of P. maackianus with the highest growth inhibition of S. capricornutum belonged to the lipophilic constituents. And the antialgal potential could be enhanced through further separation by the activity-guided fractionation.