Neuroprotective effects of Cubebin and Hinokinin lignan fractions of Piper cubeba fruit in Alzheimer’s disease in vitro model

Abstract Objectives The current research examines the protective effects of the Piper cubeba ethanolic extract and its isolated lignans; Cubebin and Hinokinin fractions against Alzheimer’s Disease (AD) in vitro model. Methods Dried and powdered fruit of P. cubeba were extracted in ethanol and fractionated using silica gel column chromatography. Of the 15 eluted fractions, two fractions indicated presence of targeted Lignans; Hinokinin and Cubebin. They were monitored by thin layered chromatography and their structures were confirmed by LC-HRMS spectrometry and NMR analysis. Antioxidant activity of the crude extract and isolated lignan fractions were analyzed using FRAP, DPPH and ABTS assays. Anti-acetylcholinesterase activity was investigated in vitro and β-amyloid (Aβ) cytotoxicity on SHSY-5Y human neuroblastoma cell lines was studied using MTT assay. Results The crude extract showed similar if not significantly stronger antioxidant capacity compared to ascorbic acid in FRAP and DPPH assays. Both lignans exerted weaker yet potent activity. The crude extract yielded the strongest acetylcholinesterase inhibitory potential compared to the lignan fractions however, there was no significant difference (p<0.05) between IC50 values of lignan fractions. Significant neuroprotective effects against 50 μM Aβ at p<0.05 was observed for selected fractions compared to Aβ treated control. The crude extract was highly protective against Aβ at both 5 and 10 μg/mL. Cubebin and Hinokinin-containing fractions significantly improved the viability of the SH-SY5Y cells against Aβ cytotoxicity both only at the concentration of 100 μg/mL. Conclusions Results from our studies suggest that these phytoconstituents might be good candidates in prevention and treatment of AD.