Antioxidant, Anti-Cholinesterase, and Neuroprotective Properties of Morus alba and Morus nigra Extracts

The Morus genus comprises several tree species whose fruits are used in human nutrition, while the leaves and roots are used in traditional medicine. The aim of this study was to highlight the antioxidant, cholinesterase inhibitory, and neuroprotective effects of hydroalcoholic extracts from Morus alba (MAE) and Morus nigra (MNE) leaves. RP-UHPLC-PDA analysis of extracts revealed the presence of polyphenols in higher quantities in MNE extract compared to MAE. Both extracts demonstrated antioxidant properties in the hydroxyl radical scavenging and lipid peroxidation inhibition assays. MNE exhibited a superior antioxidant capacity compared to MAE; the IC₅₀ values for the inhibition of plasma lipid oxidation assay were 25.31 ± 2.54 µg/mL for MNE and 29.85 ± 0.97 µg/mL for MAE. Both extracts showed cholinesterase inhibitory activity. The IC₅₀ values for acetylcholinesterase inhibition were 24.34 ± 0.86 µg/mL for MNE and 46.87 ± 2.16 µg/mL for MAE. The inhibitory potency of MNE was comparable to that of galantamine, which was used as standard. Both extracts reversed, in a dose-dependent manner, the scopolamine-induced cognitive impairment and behavioural alterations in scopolamine-treated zebrafish (Danio rerio) as evaluated by the Y-maze test, novel tank diving test, and novel object recognition test.