Ocotea alkaloids: the chaacterization and structures of four new aporphine bases

Stephapierrines A-H, new tetrahydroprotoberberine and aporphine alkaloids from the tubers of Stephania pierrei Diels and their anti-cholinesterase activities

Eight new alkaloids, which are four new tetrahydroprotoberberine alkaloids, stephapierrines A-D (1-4), and four new aporphine alkaloids, stephapierrines E-H (5-8), together with three new naturally occurring alkaloids (9-11) and thirty-four known alkaloids (12-45) were isolated from the tubers of Stephania pierrei Diels. The structures of the new compounds were elucidated by spectroscopic analysis and physical properties. The structures of the known compounds were characterized by comparison of their spectroscopic data with those previously reported. Compound 42 exhibited the strongest acetylcholinesterase (AChE) inhibitory activity, which was more active than galanthamine, the reference drug. Compound 23 showed the highest butyrylcholinesterase (BuChE) inhibitory activity, which was also more active than galanthamine. Molecular docking studies are in good agreement with the experimental results.

Acetylcholinesterase inhibitory activities and bioguided fractionation of the Ocotea percoriacea extracts: HPLC-DAD-MS/MS characterization and molecular modeling of their alkaloids in the active fraction

In vitro acetylcholinesterase activities of the hexane, dichloromethane, ethyl acetate, n-butanol and aqueous extracts of leaves of Ocotea percoriacea Kosterm. (Lauraceae) were evaluated. The bioguided fractionation of the most active extract (dichloromethane) using silica gel open-column chromatography led to an active alkaloidal fraction composed of isocorydine N-oxide, isocorydine N-oxide derivative, palmatine, roemerine and roemerine N-Oxide. The identification of the chemical structure of these compounds was carried out with high-performance liquid chromatography coupled to electrospray ionization multiple-stage mass spectrometry (HPLC-ESI-MS/MS). Aiming to understand their inhibitory activities, these alkaloids were docked into a 3D model of Electrophorus electricus Acetylcholinesterase (EelAChE) built in the Modeller 9.18 employing homology modeling approach. The results suggest that the alkaloids had the same binding mode and, possibly, the inhibition mechanism of classic drugs (ex. tacrine and donepezil). The structural difference of these compounds opens a new opportunity for the optimization of leading compounds.

Lauraceae alkaloids

Lauraceae is one of the most representative botanical families, presenting 67 genera, with over 2500 species and more than 300 different alkaloids reported, mainly isoquinolines.

Convenient synthesis of (S)-(+)-apomorphine from (R)-(-)-apomorphine

A method was devised for preparing (S)-(+)-apomorphine from (R)-(-)-apomorphine. Dehydrogenation of the dimethyl ether of (R)-(-)-apomorphine with 10% palladium-on-carbon followed by reduction with sodium cyanoborohydride under acidic conditions resulted in quantitative racemization to give (R,S)-apomorphine dimethyl ether, which then was resolved with (-)-tartaric acid. Ether cleavage of (S)-(+)-apomorphine dimethyl ether (-)-tartrate with hydriodic acid in acetic anhydride yielded (S)-(+)-apomorphine, which was isolated as the hydrochloride salt in 99% enantiomeric excess.