Phytochemical Profiling and Neuroprotective Potential of Endemic Pakistani Plant Xylosma longifolia

Abstract

Xylosma longifolia, an indigenous species of Pakistan is used traditionally in folk medicine for various diseases and only few studies have been done on its scientific pharmacological properties. The aim of this study was therefore set to comprehensively assess the phytochemical composition and neuroprotective activity of X. longifolia leaf extract. Leaves were harvested, dried and extracted with methanol followed by gas chromatography-mass spectrometry (GC-MS) analysis. Thirty-two compounds were identified, with the major compounds being β-sitosterol, lupeol and quercetin, all known for their neuroprotective effects. Significant antioxidant activity was obtained by DPPH and ABTS assays with IC₅₀ values of 142.7 ± 3.8 μg/mL and 118.3 ± 2.9 μg/mL, respectively, which is very similar to that of ascorbic acid. The neuroprotective activity was assessed by applying H₂O₂-induced oxidative damage to SH-SY5Y neuronal cells. XLE treatment showed a dose-dependent increase of cell viability between 42–87% with a reduction of intracellular ROS levels of 63% under the same conditions. XLE was shown to be significantly beneficial in cognitive function in Swiss albino mice for cognitive function in the Morris water maze and Y-maze experiments in vivo when administered orally at 200 and 400 mg/kg. Moreover, biochemical studies on brain tissue showed that treatment by XLE resulted in a decrease of acetylcholinesterase (AChE) activity and an increase in reduced glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD) levels after treatment. The results indicate that the phenolic and triterpenoid constituents of X. longifolia show potential neuroprotective effects that may be useful in the development of therapeutic agents for neurodegenerative diseases like Alzheimer's disease, and should be further explored. But it is important to isolate the single bioactive compounds and to have clinical trials in the near future to make the use of these compounds a possibility of translational applications.