Acetylcholinesterase, butyrylcholinesterase, and tyrosinase inhibition studies and antioxidant activities of 33 Scutellaria L. taxa from Turkey.

The members of Scutellaria L. (Lamiaceae) is known to be rich particularly in flavonoids and among them, S. baicalensis has been recorded to be used for memory-enhancing purpose. Therefore, we initiated a study to screen the methanol extracts prepared from the aerial parts of 33 Turkish Scutellaria species for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities, which are the key enzymes taking place in pathogenesis of Alzheimer's disease. Besides, the methanol extracts were tested in vitro against another enzyme, tyrosinase, which is associated with melanin hyperpigmentation. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenger effect, ferrous ion-chelating ability, and ferric-reducing antioxidant power (FRAP) of the ethyl acetate and methanol extracts were also determined. AChE, BChE, and tyrosinase inhibition of the extracts were performed on ELISA microplate reader by spectrophotometric method. The extracts showed weak inhibition against AChE and BChE, while the best tyrosinase inhibition was caused by the methanol extract of S. brevibracteata subsp. subvelutina. The extracts had a very high DDPH radical scavenging effect and moderate antioxidant activity in ferrous ion-chelating and FRAP tests.

Cholinesterase inhibitory activities of some flavonoid derivatives and chosen xanthone and their molecular docking studies.

Flavonoids are one of the largest classes of plant secondary metabolites and are known to possess a number of significant biological activities for human health. In this study, we examined in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities of four flavonoid derivatives--quercetin, rutin, kaempferol 3-O-beta-D-galactoside and macluraxanthone. The in vitro results showed that quercetin and macluraxanthone displayed a concentration-dependant inhibition of AChE and BChE. Macluraxanthone showed to be the most potent and specific inhibitor of both the enzymes having the IC(50) values of 8.47 and 29.8 microM, respectively. The enzyme kinetic studies revealed that quercetin inhibited both the enzymes in competitive manner, whereas the mode of inhibition of macluraxanthone was non-competitive against AChE and competitive against BChE. The inhibitory profiles of the compounds have been compared with standard AChE inhibitor galanthamine. To get insight of the intermolecular interactions, the molecular docking studies of these two compounds were performed at the active site 3D space of both the enzymes, using ICM-Dock module. Docking studies exhibited that macluraxanthone binds much more tightly with both the enzymes than quercetin. The calculated docking and binding energies also supported the in vitro inhibitory profiles (IC(50) values). Both the compounds showed several strong hydrogen bonds to several important amino acid residues of both the enzymes. A number of hydrophobic interactions could also explain the potency of the compounds to inhibit AChE and BChE.

Cholinesterase inhibitory effects of the extracts and compounds of Maclura pomifera (Rafin.) Schneider.

We have investigated anticholinesterase potential of the methanol extracts from the leaf, wood, flower, twig, and stem bark of the female and male individuals and rhizodermis and fruit from the female tree of Maclura pomifera (Rafin.) Schneider (Moraceae) along with its major isoflavonoids; osajin and pomiferin as well as their semi-synthetic derivatives; iso-osajin and iso-pomiferin. Anticholinesterase activity was determined by Ellman method using ELISA microplate reader. Osajin and pomiferin had a noticeable inhibition of AChE with IC(50) values of 2.239 and 0.096 mM, respectively, while their iso-derivatives were found to display less inhibition towards AChE. The extracts and compounds did not inhibit BChE. The extracts were analyzed for osajin and pomiferin contents by LC-DAD-MS and only the fruits and female flowers contained osajin (fruit: 8.87%, female flowers: 0.19%, w/w) and pomiferin (fruit: 13.6%, female flowers: 0.36%, w/w).

Acetylcholinesterase inhibitory and antioxidant properties of Cyclotrichium niveum, Thymus praecox subsp. caucasicus var. caucasicus, Echinacea purpurea and E. pallida.

The dichloromethane, ethyl acetate, ethanol, and aqueous extracts of Cyclotrichium niveum (CN) and Thymus praecox subsp. caucasicus var. caucasicus (TP), Echinacea purpurea (EPU), and E. pallida (EPA) along with the essential oils of CN and TP were assessed for their anti-acetylcholinesterase (AChE) and antioxidant activities. AChE inhibition was estimated using spectrophotometric method of Ellman. Antioxidant activity was evaluated by 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and ferrous ion-chelating power tests. Ferric-reducing antioxidant power (FRAP) of CN and TP were also tested. CN essential oil was found to contain isomenthone (56.21%) and pulegone (19.76%). The ethyl acetate (83.11-87.98%) and dichloromethane (73.45-84.02%) extracts of CN showed the highest AChE inhibition. The ethyl acetate and ethanol extracts of TP exerted significant DPPH scavenger effect. The water extracts of CN and TP and the chloroform extract of the aerial parts of EPU displayed the highest ferrous ion-chelating effect. The leaf and flower essential oils of TP had the best FRAP.