Structure Elucidation and Cholinesterase Inhibition Activity of Two New Minor Amaryllidaceae Alkaloids.

Two new minor Amaryllidaceae alkaloids were isolated from Hippeastrum × hybridum cv. Ferrari and Narcissus pseudonarcissus cv. Carlton. The chemical structures were identified by various spectroscopic (one- and two-dimensional (1D and 2D) NMR, circular dichroism (CD), high-resolution mass spectrometry (HRMS) and by comparison with literature data of similar compounds. Both isolated alkaloids were screened for their human acetylcholinesterase (hAChE) and butyrylcholinesterase (hBuChE) inhibition activity. One of the new compounds, a heterodimer alkaloid of narcikachnine-type, named narciabduliine (2), showed balanced inhibition potency for both studied enzymes, with IC50 values of 3.29 ± 0.73 µM for hAChE and 3.44 ± 0.02 µM for hBuChE. The accommodation of 2 into the active sites of respective enzymes was predicted using molecular modeling simulation.

Enzyme immobilization in a biomimetic silica support.

Robust immobilization techniques that preserve the activity of biomolecules have many potential applications. Silicates, primarily in the form of sol-gel composites or functionalized mesoporous silica, have been used to encapsulate a wide variety of biomolecules but the harsh conditions required for chemical synthesis limit their applicability. Silaffin polypeptides from diatoms catalyze the formation of silica in vitro at neutral pH and ambient temperature and pressure. Here we show that butyrylcholinesterase entrapped during the precipitation of silica nanospheres retained all of its activity. Ninety percent of the soluble enzyme was immobilized, and the immobilized enzyme was substantially more stable than the free enzyme. The mechanical properties of silica nanospheres facilitated application in a flow-through reactor. The use of biosilica for enzyme immobilization combines the excellent support properties of a silica matrix with a benign immobilization method that retains enzyme activity.

Ultrastructural localization of butyrylcholinesterase in senile plaques in the brains of aged and Alzheimer disease patients.

Histochemical localization of butyrylcholinesterase has been carried out in primitive, perivascular, and classic plaques in the brains of both nondemented and Alzheimer disease (AD) patients. Butyrylcholinesterase histochemistry has been compared to amyloid beta-protein (A beta P) immunocytochemistry in adjacent sections. In small primitive plaques, most of the butyrylcholinesterase reaction product appears ultrastructurally located over plasma membranes of healthy-looking cell processes. In more extensive primitive plaques, butyrylcholinesterase reaction product also decorates amyloid filaments, which become identifiable as delicate wisps. In classic plaques, large aggregates of butyrylcholinesterase reaction product colocalize with bundles of amyloid filaments, as well as with the compact amyloid core. Thus, deposition of butyrylcholinesterase in senile plaques follows a close parellelism with the progressive aggregation of amyloid beta-protein, supporting the possibility that cholinesterases may play some role in the maturation of these structures.