Mohammad I. Abdel-Hamid

Cyanobacteria comprise a good natural resource of a potential variety of neuro-chemicals, including acetylcholinesterase inhibitors essential for Alzheimer’s disease treatment. Accordingly, eight different cyanobacterial species were isolated, identified, and evaluated on their growth on different standard nutrient media. It was found that the modified Navicula medium supported the highest growth of the test cyanobacteria. The effects of methylene chloride/methanol crude extracts of the test cyanobacteria on acetylcholinesterase activity were examined and compared. Anabaena variabilis (KU696637.1) crude extract recorded the highest acetylcholinesterase inhibition (62 ± 1.3%). Navicula medium chemical components were optimized through a Plackett–Burman factorial design. The biomass of Anabaena variabilis increased significantly when grown on the optimized medium compared to that of control. The chemical analysis of the fractions derived from Anabaena variabilis showed the presence of two compounds in significant amounts: the flavonoid 5,7-dihydroxy-2-phenyl-4H-chrome-4-one and the alkaloid 4-phenyl-2-(pyridin-3-yl) quinazoline. Molecular docking studies revealed that both compounds interact with the allosteric binding site of acetylcholinesterase at the periphery with π-π stackings with Tyr341 and Trp286 with good, predicted partition coefficient. The compounds obtained from this study open the door for promising drug candidates to treat Alzheimer’s disease for their better pharmacodynamics and pharmacokinetic properties.

Effects of 12 heavy metals on growth of free and alginate-immobilized cells of the alga Pseudokirchneriella subcapitata were investigated. The tested metals ions include Al, As, Cd, Co, Cr, Cu, Hg, Se, Ni, Pb, Sr, and Zn. Toxicity values (EC₅₀) were calculated by graphical interpolation from dose-response curves. The highest to the lowest toxic metals are in the order Cd > Co > Hg > Cu > Ni > Zn > Cr > Al > Se > As > Pb > Sr. The lowest metal concentration (mg L⁻¹) inhibiting 50% (EC₅₀) of algal growth of free and immobilized (values in parentheses) algal cells were, 0.018 (0.09) for Cd, 0.03 (0.06) for Co, 0.039 (0.06) for Hg, 0.048 (0.050) for Cu, 0.055 (0.3) for Ni, 0.08 (0.1) for Zn, 0.2 (0.3) for Cr, 0.75 (1.8) for Al, 1.2 (1.4) for Se, 3.0 (4.0) for As, 3.3 (5.0) for Pb, and 160 (180) for Sr. Free and immobilized cultures showed similar responses to Cu and Se. The free cells were more sensitive than the immobilized ones. Accordingly, the toxicity (EC₅₀) of heavy metals derived only form immobilized algal cells might by questionable. The study suggests that batteries of alginate-immobilized algae can efficiently replace free algae for the bio-removal of heavy metals.

Raw water samples of two drinking water treatment plants (named New Mansoura and Bilqas stations) were collected for a full annual cycle. Analyses of total soluble inorganic N, dissolved reactive phosphorus (DRP) and Total dissolved phosphorus (TDP) were carried out. Qualitative and quantitative analysis of Cyanoprokaryotes and photosynthetic pigments of phytoplankton were investigated. Total microcystins of raw water supply and potable water were seasonally analyzed using ELISA. Seven Cyanobprokaryotes species were isolated, cultured under lab conditions and biomass contents of microcystin–LR and -YR were analyzed using HPLC. Physico-chemical characteristics and photosynthetic pigments displayed pronounced periodic variations. Species composition and abundance of Cyanoprokaryotes exhibited marked seasonal variation during the period of study. Cyanoprokaryotes biovolume peaked in summer at New Mansoura (214.3mm3m-3) and Bilqas (161.3 mm3m-3) water treatment stations. The minimum mean biovolume of 25.2 and 30.8 mm3m-3 were recorded in winter at New Mansoura and in autumn at Bilqas station, respectively. Total microcystins in raw water maintained seasonal variations. Microcystins values were 2.2 and 2.0 µg l-1 during summer at Bilqas and New Mansoura respectively. Theses values of 1µg l-1 exceeding the WHO guidelines. Total microcystins of potable water were below the WHO guideline except in summer at New Mansoura (1.2µg l-1). Microcystins in biomass of different species of Cyanoprokaryotes varied between 3.0 mg g-1 (8% LR and 92%YR) and 0.3 mg g-1 (100% LR) recorded for Anabaena oryzae and Anabaena khannae, respectively.