Ishrak Khafagi

The efficiency of random versus ethno-directed research in the evaluation of Sinai medicinal plants for bioactive compounds

Hexane, ethyl acetate and ethanol extracts of sixty plant species (growing wild in Sinai, Egypt) were screened for antibacterial and antifungal activities against a range of Gram-positive and Gram-negative bacteria, a yeast and dermatophytic fungi. Plants were collected either by random or ethno-directed methods. Plants collected at random (36 species) were gathered from different districts of Sinai, while the ethnobotanical collection (24 species) comprised species used in the folk medicine of the Bedouins in Sinai. Results indicate that plant sampling based on ethnobotanical approach produced greater number of plants showing antimicrobial activity. The results are discussed with respect to the ethnobotanical correlation of active species.

Enhancement of oleandrin production in suspension cultures of Nerium oleander by combined optimization of medium composition and substrate feeding

Abstract Oleandrin has been identified as the most potent antitumor ingredient of the Mediterranean herb Nerium oleander L. A strategy for optimization of medium compositions and conditions was developed for enhanced oleandrin production in suspension cultures from leaf-origin explants of Nerium oleander. The cell suspension cultures were grown in various modifications of MS medium as a basal medium. The effects of different natural extracts, plant growth substances, carbon and nitrogen sources and phosphate on the growth and oleandrin accumulation were investigated as well as effect of light, pH, shaking speed and substrate feeding. The highest oleandrin yield was obtained when the nitrogen concentration was lowered to two-thirds and the phosphate concentration increased by two-thirds of that specified in the MS medium in the presence of 3% sucrose, coconut milk, indolebutyric acid and benzyladenine in concentrations of 1 and 2 mg l−1, respectively. Lower pH and faster shaking speed favored oleandrin accumulation. Chemical feeding of progesterone and cholesterol boosted the oleandrin concentration to higher levels reaching 8.23±0.05 mg g−1 dry weight. This was about 10-fold higher than that detected in field-grown plants using the same extraction and analytic conditions, and about 24-fold higher than that determined in control cultures with regular MS medium and without precursor feeding.

Variations in the Bioaccumulation Rates of Heavy Metal by Immobilized and Free Gramnegative and Gram - Positive Bacterial Cells Isolated from an Aerated Lagoon

The uptake of heavy metals by all immobilized microbial cell strains (bacterial beads: bacterial cells in alginate) is better than by free cells. The average removal percentage for all six metals by Gram-positive bacterial beads showed that Bacillus megaterium (81%), Bacillus flexus (73%), Bacillus amyloliquefaciens (70%) and Bacillus cereus (66%). While Immobilized Gram-negative cells of Pseudomonas veronii and Rahnella aquatilis were good for the uptake of metals such as copper, nickel and cobalt. Rahnella aquatilis and Pseudomonas veronii accumulated Cu, Ni and Co by respectively (91.5%, 77 %), (90.1%, 85 %) and (75%, 74%), while Pb was only accumulated by Pseudomonas veronii (67 %). On the other hand, Sphingobacterium daejeonense and Roseomona saquatica were relatively weak in accumulating heavy metals. On the other hand, the uptake of heavy metals by all free microbial cell strains possessed no significant difference by varying metals type and bacterial strains, except Co and Pb were poorly accumulated. Immobilization in alginate beads provides a protective environment for these agents for sufficient time of heavy metals removal. Immobilized systems currently offer various advantages over free systems. Rahnella aquatilis was reported for the first time in this research as a potential organism for the bioaccumulation of some toxic heavy metals from domestic wastewaters.