Multifunctional activity of some isoquinoline alkaloids from Corydalis cava tubers on Alzheimer's disease targets

Fifteen previously isolated Corydalis cava alkaloids have been investigated for their potential multifunctional activity on Alzheimer's disease (AD) targets. Determination of ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibition was carried out using a BACE1-Immobilized Enzyme Reactor (IMER) by validating the assay with a multi-well plate format Fluorescence Resonance Energy Transfer (FRET) assay. Seven alkaloids out of fifteen were found to be active, (-)-corycavamine (IC50 FRET= 41.16 ± 7.82µM; IC50 IMER= 1690 ± 545.0µM) and (+)-corynoline (IC50 FRET = 33.59 ± 0.23µM; IC50 IMER = 89.07 ± 15.08µM) demonstrated the highest BACE1 inhibition activity, in the micromolar range, in a concentration dependent manner. BACE1-IMER was found to be a valid device for the fast screening of inhibitors and the determination of their potency. In a permeation assay (PAMPA) for the prediction of blood-brain barrier (BBB) penetration, the most active compounds (-)-corycavamine (Pe = 16.3 ± 0.9 × 10-6 cm s-1) and (+)-corynoline (Pe = 11.7 ± 0.1 × 10-6 cm s-1) were found to be able to cross the BBB. Not all compounds showed activity against glycogen synthase kinase-3β (GSK-3β) and casein kinase-1δ (CK-1δ). Furthermore, on the basis of the reported results, we found that some Corydalis cava alkaloids have multifunctional activity against AD targets (prolyl oligopeptidase, cholinesterases, and BACE1). Moreover, we tried to elucidate the treatment effectivity (rational use) of its extract in memory dysfunction in folk medicine. Based on a HPLC-UV analysis we found that due to quantitative low content of compounds with neuroprotective activity in the plant material, the use of C. cava extracts in the therapy of memory dysfunction in folk medicine is not corroborated by ascertained data .