Comparative evaluation of neuroprotective effect of three varieties of Allium cepa in chronic constriction injury induced neuropathic pain

Abstract

Allium cepa has been used extensively for culinary purposes as well as in traditional system of medicine. A number of varieties of A. cepa are available commercially with varietal differences in phytoconstituents and biological activities. However their effect on neuropathic pain has not been explored. The present study was designed to compare the effectiveness of three varieties of A. cepa in neuropathic pain. Materials & Methods: Methanol extracts and flavonoid-rich fractions (FRF) of outer scales of three varieties of A. cepa viz. Agrifound Dark Red (ADR), Agrifound White (AW) and NHRDF-Red (L28) were prepared. These were standardized with reference to their total phenol and flavonoid content. The marker- quercetin was determined by High Performance Thin Layer Chromatography (HPTLC). The effect of the prepared extracts was studied on neuropathic pain (NP) induced by chronic constriction injury (CCI) in rats. Behavioral indices of sensory dysfunction due to NP were evaluated by studying various behavioral tests viz. pin prick test, Eddy’s hot plate test and Randall-Selitto test for hyperalgesia, and acetone drop test for allodynia. Markers of oxidative stress were studied by determining Thio-barbituric Acid Reactive Species (TBARS) and reduced glutathione (GSH) levels. Results: FRF of variety L28 produced the most significant reduction of thermal and mechanical hyperalgesia and amelioration of cold allodynia. This also attenuated the CCI-induced increase in TBARS and decrease in GSH levels. Conclusion: L28 was found to contain highest amount of flavonoids and quercetin as compared to other varieties. These results indicate that FRF of A. cepa variety L28 may be a potential candidate for the management of NP.