Screening for acetylcholinesterase inhibition, lipid peroxidation inhibition and antioxidant activity of medicinal plants from Morocco / Detección de inhibición de acetilcolinesterasa, inhibición de peroxidación de lípidos y actividad antioxidante de plantas medicinales de Marruecos

Acetylcholinesterase (AChE), hydrolyzes acetylcholine to choline and acetate, thereby terminating this neurotransmitter effect at cholinergic synapses. Therefore, AChE inhibition is used for counterbalance the cholinergic deficit in Alzheimer's disease (AD) patients. In the present work, in order to find new plant acetylcholinesterase inhibitors, the hydroalcoholic extracts from seventeen medicinal plant species were screened for their acetylcholinesterase inhibition activity, as well as total phenolic (TPC) and flavonoids contents (TFC) and antioxidant activity using ORAC (Oxygen Radical Absorbance Capacity) assay, and their ability to inhibit lipid peroxidation. The results revealed that Rumex acetosa, Taraxacum officinale and Hypericum perforatum extracts possessing the highest TPC and TFC, were the most effective in terms of ORAC antioxidant activity, and acetylcholinesterase inhibition, in addition to their ability to inhibit liposomes peroxidation, suggesting that those plant species may provide a substantial source of secondary metabolites, which act as natural antioxidants and acetylcholinesterase inhibitors, and may be beneficial in the treatment of AD.

La acetilcolinesterasa (AChE) hidroliza la acetilcolina se hidroliza en colina y acetato, terminando así este efecto neurotransmisor en las sinapsis colinérgicas. Por lo tanto, la inhibición de la AChE se utiliza para contrarrestar el déficit colinérgico en pacientes con enfermedad de Alzheimer (EA). En el presente trabajo, con el fin de encontrar nuevos inhibidores de la acetilcolinesterasa vegetal, se analizaron los extractos hidroalcohólicos de diecisiete especies de plantas medicinales para determinar su actividad inhibidora de la acetilcolinesterasa, así como el contenido total de fenólicos (TPC) y flavonoides (TFC) y la actividad antioxidante utilizando ORAC (Capacidad de absorbancia de radicales de oxígeno) y su capacidad para inhibir la peroxidación de lípidos. Los resultados revelaron que los extractos de Rumexacetosa, Taraxacum officinale e Hypericum perforatum que poseen los más altos TPC y TFC, fueron los más efectivos en términos de actividad antioxidante ORAC e inhibición de acetilcolinesterasa, además de su capacidad para inhibir la peroxidación de los liposomas, sugiriendo que esas especies de plantas puede proporcionar una fuente sustancial de metabolitos secundarios, que actúan como antioxidantes naturales e inhibidores de la acetilcolinesterasa, y puede ser beneficioso en el tratamiento de la EA.

Biological screening of herbal extracts and essential oil from Plectranthus species: α-amylase and 5-lipoxygenase inhibition and antioxidant and anti-Candida potentials

Abstract The phenolic compound content, the antioxidant and α-amylase inhibition potentials of different extracts of the Plectranthus amboinicus, P. barbatus and P. ornatus were evaluated. We also evaluated the influence of plant growth and harvest time on the chemical composition of the essential oil (EO) of P. amboinicus, its antioxidant and anti-Candida activities and the α-amylase and lipoxygenase inhibitions. The turbo-extract of P. barbatus showed the greatest phenolic compound content and antioxidant activity. No α-amylase inhibition activity was observed in the analyzed extracts, but the turbo-extraction and refluxing extracts possessed high antioxidant activities. Protected cultivation and morning harvest conditions gave the best antioxidant activities, which was associated to the highest carvacrol content. P. amboinicus EO antioxidant activity could contribute to the reduction of oxidative stress in diabetes. Causal Candida strains of diabetic foot ulcers showed sensitivity to P. amboinicus EO. C. albicans and C. dubliniensis were the most sensitive of the selected Candida strains. Turbo-extracts or refluxing of the three species extracts and the EO of P. amboinicus should be considered as a potential candidate for the management the complications of type 2 diabetes.

Phenol content and antioxidant activity of different young and adult plant parts of tobacco from Tunisia, dried at 40 and 70 ºC.

Different parts of tobacco plants were dried at 40 and 70 ºC. Some of them were also dried at room temperature. Dried plant material was extracted by sonication for obtaining hydro-alcoholic extracts (70%). Total phenol and total flavonoids were determined as well as antioxidant activities which were evaluated through different methods (capacity for scavenging DPPH, ABTS, superoxide and hydroxyl radicals; capacity for preventing lipid peroxidation using egg yolk as substrate; and reducing power). In young and adult plants, leaves generally had higher amounts of phenols (14.46-23.05 mg GAE g-1) than the remaining parts of the plant, independent on the temperature used. Generally, roots had lower amounts of phenols (1.56-4.63 mg GAE g-1). Leaves and flower had significantly higher concentrations of flavonoids (3.08-4.17 mg QE g-1 and 1.17-2.12 mg QE g-1, respectively) than the remaining parts. The antioxidant activity was generally higher in leaf extracts, although stalk ones had also a good capacity for scavenging hydroxyl radicals. Generally, young plants had the best capacity for scavenging DPPH and hydroxyl free radicals which may be related with the phenol content. Concerning drying temperatures, the results were not conclusive.