Design,synthesis, and evaluation of 3,7-substituted coumarin derivatives as multifunctional Alzheimer’s disease agents

Multitarget directed ligands (MTDLs) are emerging as promising treatment options for Alzheimer’s disease (AD). Coumarin derivatives serve as a good starting point for designing MTDLs due to their inherent inhibition of monoamine oxidase (MAO) and cholinesterase enzymes, which are complicit in AD’s complex pathophysiology. A preliminary series of 3,7-substituted coumarin derivatives were synthesised and evaluated for enzyme inhibitory activity, cytotoxicity as well as neuroprotective ability. The results indicated that the compounds are weak cholinesterase inhibitors with five compounds demonstrating relatively potent inhibition and selectivity towards MAO-B with IC₅₀ values between 0.014 and 0.498 hx00B5;µM. Significant neuroprotective effects towards MPP⁺-compromised SH-SY5Y neuroblastoma cells were also observed, with no inherent cytotoxicity at 10 µM for all compounds. The overall results demonstrated that substitution of the phenylethyloxy moiety at the 7-position imparted superior general activity to the derivatives, with the propargylamine substitution at the 3-position, in particular, displaying the best MAO-B selectivity and neuroprotection.     

Forest biomass,productivity and carbon cycling along a rainfall gradient in West Africa

Net Primary Productivity (NPP) is one of the most important parameters in describing the functioning of any ecosystem and yet it arguably remains a poorly quantified and understood component of carbon cycling in tropical forests, especially outside of the Americas. We provide the first comprehensive analysis of NPP and its carbon allocation to woody, canopy and root growth components at contrasting lowland West African forests spanning a rainfall gradient. Using a standardized methodology to study evergreen (EF), semi‐deciduous (SDF), dry forests (DF) and woody savanna (WS), we find that (i) climate is more closely related with above and belowground C stocks than with NPP (ii) total NPP is highest in the SDF site, then the EF followed by the DF and WS and that (iii) different forest types have distinct carbon allocation patterns whereby SDF allocate in excess of 50% to canopy production and the DF and WS sites allocate 40%–50% to woody production. Furthermore, we find that (iv) compared with canopy and root growth rates the woody growth rate of these forests is a poor proxy for their overall productivity and that (v) residence time is the primary driver in the productivity‐allocation‐turnover chain for the observed spatial differences in woody, leaf and root biomass across the rainfall gradient. Through a systematic assessment of forest productivity we demonstrate the importance of directly measuring the main components of above and belowground NPP and encourage the establishment of more permanent carbon intensive monitoring plots across the tropics.     

Adamantane amine-linked chloroquinoline derivatives as chloroquine resistance modulating agents in Plasmodium falciparum

Previously we have shown that pentacycloundecylamine-chloroquinoline (PCU-CQ) conjugates possess significant chemosensitizing abilities and can circumvent the resistance associated with chloroquine (CQ) resistant plasmodia. In order to further explore structurally related polycyclic compounds as reversed CQ agents we synthesized a series of eight aza-adamantanol (1–4) and adamantane-imine (5–8) CQ conjugates. All conjugates showed limited cytotoxicity against CHO cells (IC₅₀?>?37?µM). Compounds 1, 2 and 5 were highly active (K1 IC₅₀?<?100?nM) exhibiting a 3–4-fold increase in antiplasmodial activity against CQ resistant strain K1 compared to CQ. Reduced cross-resistance (resistance index, RI: 2–4.3) relative to CQ (RI?=?38) was also observed for these compounds. Compound 1 which showed an 18-fold enhancement at retaining its activity against the K1 strain compared to CQ is a promising candidate to substitute CQ in P. falciparum resistant malaria.     

Cephapirin: In Vitro Antibacterial Spectrum

Cephapirin, a new semisynthetic cephalosporin derivative, was found to have an antibacterial spectrum similar to that of cephalothin. Staphylococcus aureus was inhibited by cephapirin concentrations of 0.09 to 12.5 mug/ml. S. epidermidis, S. viridans, S. pyogenes, and Diplococcus pneumonia isolates were inhibited by less than 1 mug/ml. The Enterococcus required a concentration of 25 mug of antibiotic per ml for inhibition. Approximately 65% of Escherichia coli, and all Klebsiella, indole-negative Proteus, and Salmonella strains tested were inhibited by the drug. Serratia, Pseudomonas, indole-positive Proteus, and Erwinia strains were highly resistant. Inoculum size was not an important factor in determining the level of sensitivity of S. aureus to cephapirin. The antibiotic does not appear to be significantly bound to serum protein. In vitro development of resistance to the drug was demonstrated with two isolates of S. aureus.     

Vitellogenesis and oocyte development in azadirachtin-induced fifth-instar overage nymphs of Locusta migratoria (L.)

Injection of azadirachtin into females of Locusta migratoria at the beginning of the last nymphal instar prevented molting to the adult stage, and many of these locusts survived for long periods as overage fifth-instar nymphs. Overage female nymphs synthesized vitellogenin; maximum vitellogenin content in their hemolymph was 6–7 times higher than that found in normal adult females. The overage female nymphs developed vitellogenic oocytes, but development was retarded to some extent: although vitellogenin did accumulate in the proximal oocytes, their maximum average length was only about 2.8 mm (compared to 6.2 mm in normal adult females) and extensive oocyte resorption was observed. Thus, attainment of adult competence of the organs and processes involved in female reproduction is independent to a considerable extent from the process of overt adult morphogenesis.     

Choosing in Freedom or Forced to Choose? Introspective Blindness to Psychological Forcing in Stage-Magic

We investigated an individual ability to identify whether choices were made freely or forced by external parameters. We capitalized on magical setups where the notion of psychological forcing constitutes a well trodden path. In live stage magic, a magician guessed cards from spectators while inquiring how freely they thought they had made the choice. Our data showed a marked blindness in the introspection of free choice. Spectators assigned comparable ratings when choosing the card that the magician deliberately forced them compared to any other card, even in classical forcing, where the magician literally handles a card to the participant This observation was paralleled by a laboratory experiment where we observed modest changes in subjective reports by factors with drastic effect in choice. Pupil dilatation, which is known to tag slow cognitive events related to memory and attention, constitutes an efficient fingerprint to index subjective and objective aspects of choice.     

Antioxidant properties of 4-quinolones and structurally related flavones

Neurodegenerative disorders are frequently associated with increased oxidative damage to the brain as a result of free radicals produced by cellular respiration. The onset and progression of neurodegeneration may therefore be curbed by exogenous hydrogen-donating antioxidant moieties such as the naturally occurring flavonoids. A series of 2-phenylquinolin-4(1H)-ones was synthesised and displayed moderate to high antioxidant activity when compared to structurally related flavones and quinolines. Activity of the hydroxy-2-phenylquinolin-4(1H)-ones (8-10) was established in reducing ferrous ions and diminishing hydrogen peroxide and hydroxyl radical production, in the FRAP (1.41-97.71% Trolox equivalents), ORAC (9.18-15.27 μM Trolox equivalents at 0.00 1mM) and TBARS (0.05-0.72 nmol MDA/mg tissue) assays, respectively. The results indicated that the additional hydrogen donating groups on the synthesised 2-phenylquinolin-4(1H)-one series increased antioxidant activity.     

Integrin regulation by vascular endothelial growth factor in human brain microvascular endothelial cells: role of alpha6beta1 integrin in angiogenesis

The precise role of vascular endothelial growth factor (VEGF) in regulating integrins in brain microvascular endothelial cells is unknown. Here, we analyzed VEGF effects on integrin expression and activation in human brain microvascular endothelial cells (HBMECs). Using human cDNA arrays and ribonuclease (RNase) protection assays, we observed that VEGF up-regulated the mRNA expression of alpha(6) integrin in HBMECs. VEGF significantly increased alpha(6)beta(1) integrin expression, but not alpha(6)beta(4) integrin expression in these cells. Specific down-regulation of alpha(6) integrin expression by small interfering RNA (siRNA) oligonucleotides inhibited both the capillary morphogenesis of HBMECs and their adhesion and migration. Additionally, VEGF treatment resulted in activation of alpha(6)beta(1) integrins in HBMECs. Functional blocking of alpha(6) integrin with its specific antibody inhibited the VEGF-induced adhesion and migration as well as in vivo angiogenesis, and markedly suppressed tumor angiogenesis and breast carcinoma growth in vivo. Thus, VEGF can modulate angiogenesis via increased expression and activation of alpha(6)beta(1) integrins, which may promote VEGF-driven tumor angiogenesis in vivo.