This study includes isolation, purification, and identification of algae from different aquatic environments in Baghdad University, Jadiria during the year 2008. Three different plant species belonging to different families were selected namely, Albizia lebbeck, Euphorbia peplus, and Callistemon viminalis for their leaves and flowers samples.
Phenols, alkaloids, and terpens were extracted from each part. The antialgal activity of type of extracts were evaluated.
Different concentrations (5, 10, and 20 mg/ml) of these compounds were prepared and their antagonistic activity was studied.
The resulted inhibition zones in mm. of diameter after 24 h. incubation of algae in 26±1°C and 200 μE/m2/Sec. were considered.
Results showed that Lyngbya limnetica was the most sensitive to these extracts and the diameter of inhibition zone was 18.22 mm. However, Microcystis aeruginosa was less sensitive than all other algae used in this study and the diameter of inhibition zone was 14.2 mm.
Also the results showed that terpenoids extract was the most active against algae and alkaloids extract had less antagonistic activity comparing with all other extracts and the inhibition zone diameters were 17.16- 12.81 mm. respectively. The extract obtained from C. viminalis flowers was the most effective in algal control compared with all other extracts and the inhibition zone diameter was 17.86 mm.
E. peplus flower and leaf extract was the less effective on algal growth achieving, a diameter of inhibition zone was 10.3 mm.
The concentration of 20 mg/ml from extract was the most effective against algae and the highest inhibition zone resulted (19.39 mm.) comparing with the concentration of 5 mg/ml from extract which was low inhibition zone diameter 11.9 mm.
The growth of Anabaena cylindrica, Nostoc commune, and Microcystis aeruginosa were stimulated by phenolic compounds extracted only from flower and leaf of E. peplus. While alkaloid extracts obtained from E. peplus had no effect against all algae at all concentrations used. Also, alkaloid extracts obtained from Albizia lebbeck leaves in all concentrations showed no effect against Scenedsmus dimorphus only.