Recent Developments in Tacrine-based Hybrids as a Therapeutic Option for Alzheimer's Disease.

Alzheimer's disease (AD) is a multifactorial, irreversible, and age-related neurodegenerative disorder among the elderly. AD attracts attention due to its complex pathogenesis, morbidity and mortality rates, and the limitations of drugs used in the treatment of AD. Cholinesterase inhibitors and N-methyl-D-aspartate (NMDA) receptor antagonists are used in the clinic. While tacrine, donepezil, galantamine, and rivastigmine are cholinesterase inhibitors, memantine is a non-competitive NMDA receptor antagonist. However, these drugs could not delay the progress of AD. The traditional clinical approach which is the one drug-one target concept is not entirely effective in the treatment of AD. Also, it is of high-priority to develop potent and novel anti-AD drugs by the design concept of multitarget directed ligands (MTDLs) which combine pharmacophores interacting with different pathways in AD. This article provides an overview of the noteworthy structural modifications made to tacrine to develop novel candidates for anti-Alzheimer drugs. Due to the complex pathology of AD, multifunctional tacrine-based ligands targeting different hallmarks, ß-amyloid, tau protein, N-methyl-Daspartate receptor, cholinesterases, monoamine oxidases, secretases, have been studied. Here, tacrinebased derivatives including heterocyclic structures such as dihydroxypyridine, chromene, coumarin, pyrazole, triazole, tetrahydroquinolone, dipicolylamine, arylisoxazole were reported with promising anti-AD effects compared to tacrine. In vitro and in vivo assays showed that new tacrine-based hybrids, which are selective, neuroprotective, and non-hepatotoxic, might be considered as remarkable anti-AD drug candidates for further clinical studies.

Solidified Floating Organic Drop Microextraction for the Detection of Trace Amount of Lead in Various Samples by Electrothermal Atomic Absorption Spectrometry.

A novel method was developed for determination of trace amounts of lead in water and food samples. Solidified floating organic drop microextraction was used to preconcentrate the lead ion. After the analyte was complexed with 1-(2-pyridylazo)-2-naphthol, undecanol and acetonitrile were added as extraction and dispersive solvent, respectively. Variables such as pH, volumes of extraction and dispersive solvents, and concentration of chelating agent were optimized. Under the optimum conditions, the detection limit of Pb (II) was determined as 0.042 µg L-1 with an enrichment factor of 300. The relative standard deviation is <10%. Accuracy of the developed procedure was evaluated by the analysis of certified reference material of human hair (NCS DC 73347) and wastewater (SPS-WW2) with satisfactory results. The developed procedure was then successfully applied to biscuit and water samples for detection of Pb (II) ions.