Assessment of antioxidative activity of alkaloids from Huperzia selago and Diphasiastrum complanatum using in vitro systems.

Free radical-induced oxidative damage is implicated in the pathogenesis of neurodegenerative disorders, and antioxidants are presumably of therapeutic value in such diseases. Our previous data indicated that free radicals are strongly associated with brain aging and also play an important role in cytotoxicity of amyloidogenic proteins including -synuclein and amyloid , which accumulate in brains during Parkinson's and Alzheimer's diseases. Disruption of the equilibrium of pro-oxidants and antioxidants results in oxidative stress that leads to the modification of DNA, proteins, carbohydrates, and lipids. It is widely accepted that antioxidants acting as radical scavengers protect the brain against oxidative damage in neurodegenerative diseases. Plant products are rich sources of phytochemicals and have been found to possess a variety of biological activities, including antioxidative potential. The aim of this study was to analyse the antioxidative potential of alkaloid fractions from Huperzia selago and Diphasiastrum complanatum to protect macromolecules against oxidative damage. Thin layer chromatography (TLC) and high-performance liquid chromatography with diode array (HPLC-DAD) and electrospray ionisation mass spectrometric detection (ESI-MS/MS) were used to carry out a comprehensive characterization of alkaloids isolated from the plant material. The effect of the tested compounds on iron/ascorbate-induced lipid peroxidation and carbonyl group formation was analysed in the rat brain homogenate. Direct free radical scavenging (DPPH assay) and the effect on dityrosine formation were measured in cell-free systems. Our results indicated that a number of alkaloid extracts at concentration of 25 µg/ml exhibited antioxidant activity as indicated by DPPH radical scavenging potential (up to 59% inhibition) and inhibition of dityrosine formation. Selected alkaloid fractions provided significant protection against lipid peroxidation and protein oxidation in rat brain tissue homogenate, reducing iron/ascorbate-induced damage by about 20% and 76%, respectively. Overall, the results indicated that selected alkaloids isolated from Huperzia selago effectively protect macromolecules from oxidative stress injury, which will give us an insight into the potential of alkaloids in terms of opening up a new therapeutic approach for oxidative stress-dependent disorders.