n-Butanol fraction from Hedysarum alpinum L. attenuates scopolamine-induced memory impairment in rats

Introduction: Hedysarum alpinum L. (HA) contains considerable amounts of polyphenols and saponins, and exhibits immune-enhancing and antiviral properties. Evidence indicates that triterpenoid saponins possess neuroprotective effects against neurodegenerative damage. The present study evaluated the effect of an HA saponin-rich n-butanol fraction (HABF) on cognitive deficits induced by scopolamine in a rat model. Methods: Cognitive impairment was assessed using passive avoidance (PA) and novel object recognition (NOR) tasks. Total triterpene saponins of HABF were quantified by the colorimetric method using oleanolic acid as a standard compound. Biochemical analyses of hippocampus tissue included measurements of acetylcholinesterase (AChE) activity, choline acetyltransferase (ChAT), catalase (CAT), and tumor necrosis factor-α (TNF-α). Results: HABF contained ۱۳۱ ± ۰.۰۲ mg oleanolic acid equivalent (OAE)/g of total triterpene saponins. Scopolamine significantly impaired memory, as shown by a decreased discrimination index in the NOR test and reduced retention latency in the PA test. Pretreatment with HABF (۴۰ and ۸۰ mg/kg) significantly alleviated the memory deficits in both tasks. Scopolamine significantly increased AChE activity and TNF-α levels, and decreased CAT activity compared to the vehicle-treated group. These alterations were significantly reversed by HABF treatment, whereas ChAT activity remained unchanged compared with the MPTP-treated group. Conclusion: HABF, rich in triterpene saponins, ameliorates scopolamine-induced memory impairment, likely through the inhibition of AChE activity and modulation of oxidative stress and inflammation. These findings may suggest its potential neuroprotective effect in cognitive dysfunction.