Comparison of three different extracts of Centella asiatica for anti-amnesic, antioxidant and anticholinergic activities: in vitro and in vivo study

Centella asiatica (CA) has been used by Ayurvedic medical practitioners in India for almost 3000 years. The neuropharmacological properties of CA and its constituents have been studied extensively. Anti-oxidant, free radical scavenging and cholinergic modulatory activities are the reported mechanisms of action for its efficacy in memory disorders. Its medicinal values are mainly attributed to the presence of several triterpenes, namely asiatic acid, madecassic acid, asiaticoside, and madecassoside. The present study was aimed to investigate the role of these triterpenes content in CA extract on the antioxidant, cholinesterase modulation and anti-amnesic properties. The fractions of CA extract enriched for (CAE-EF) and depleted/freed of (CAE-FF) triterpenes contents were compared with methanolic extract (CAE). Both in vitro and in vivo methods for evaluation of antioxidant and anticholinergic activities were used. In vitro, free radical scavenging assays (ABTS, DPPH, NO, NORAC, and ORAC) and cholinesterase (AChE and BuChE) inhibition assays were used. For evaluation of anti-amnesic effect, scopolamine induced amnesia in rats, as the acute model of memory loss was used. Following behavioural assessments (MWM, PA, EPM), biomarkers of oxidative stress (reduced GSH, MDA and SOD activity) and cholinesterase (AChE and BuChE) status were also estimated in cerebral cortex and hippocampus of rat brain. The methanolic extract (CAE) was found to perform best among all three fractions for in vitro free radical scavenging, cholinesterase inhibition, improvement of scopolamine-induced amnesia and also in vivo antioxidant effect and cholinesterase inhibitory activities. Interestingly triterpenes free fraction (CAE-FF) showed better antioxidant activity than triterpenes enriched fraction (CAE-EF) along with comparable anti-amnesic effect. This indicates that triterpenes are not solely responsible for antioxidant activity, cholinesterase inhibitory and anti-amnesic effect of CA.