The present research investigates the biological profile of eight symmetrical diheteroarylureas and phenylheteroarylureas, testing their hypothetical cytokinin-like activity and rooting activity. Cytokinin-like activity was assayed by the betacyanin (so-called amaranthin) accumulation test and by the tomato regeneration test. The rooting activity was assessed using the mung bean rooting test, the apple stem slice test and the rooting of apple microcuttings. Three compounds, 1,3-di(pyrazin-2-yl)urea (3a), 1,3-di(benzo[d] oxazol-5-yl)urea (3b) and 1,3-di(benzo[d]oxazol-6-yl)urea (3c), enhanced adventitious root formation in apple stem slice test, but only 3b and 3c were active in the mung bean rooting test. Compound 3b, that showed the best rooting activity, was also able to enhance the adventitious root formation in apple microcuttings. None of the compounds showed cytokinin-like activity.
Dual-acting compounds that combine H(3) antagonism with anticholinesterase properties are currently emerging as a novel and promising therapeutic approach in the treatment of multifactorial disorders primarily characterized by cholinergic deficits such as Alzheimer's disease. A series of novel nonimidazole H(3) ligands was developed from the chemical manipulation of 1,1'-octa-, -nona-, and -decamethylene-bis-piperidines--H(3) antagonists that had been the subject of previous investigations. These compounds were evaluated for in vitro binding affinity, antagonistic potency, and selectivity at rodent and human histamine H(3) receptors, inhibitory activity at rat brain cholinesterase, and in vivo CNS access and cholinomimetic effects. Within the present series, the tetrahydroaminoacridine hybrid 18 stands out as one of the most attractive molecules, synergistically combining nanomolar and selective H(3) antagonism with remarkable anticholinesterase activity. From this original starting point, it is hoped that future investigations will lead to dual-acting compounds that can selectively enhance central cholinergic neurotransmission and thus facilitate the treatment of cognitive disorders.
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