To evaluate and compare the antioxidant and acetylcholinestrase (AChE)-inhibitory properties of aerial parts of Strophanthus preussii (leaves, stem and root named as SPL, SPS and SPR, respectively) while catechin served as standard.The antioxidant and AchE-inhibitory properties of the methanol extracts of SP were evaluated by standard in vitro methods viz: DPPH (2,2-diphenyl-1-picrylhydrazine), nitric oxide (NO), hydroxyl radical (OH-) and hydrogen peroxide (H2O2) radical scavenging assays as well as reducing power, Fe2+/ascorbate-induced lipid peroxidation (LPO) and AChE inhibition assays. The total phenolic and flavonoid contents of the extracts were also estimated.High phenolic and flavonoid contents were found in the aerial parts of Strophanthus preussii. The amount of phenolic and flavonoids contents followed the order SPL > SPR > SPS at 250─1000 µg/ml. The results revealed that all the extracts showed antioxidant activities in vitro. However, SPL had the highest DPPH, H2O2 and OH radical scavenging abilitie, while the reducing power of the extracts followed the order SPR > SPL > SPS at 1000 µg/ml. In addition, SPL, SPS and SPR significantly inhibited LPO in rat liver by 42%, 23%, 35% and in rat brain by 68%, 31% and 51%, respectively. The LPO inhibitory activities of SPL were statistically similar to the standard. Only SPS produced significant NO scavenging effects among the extracts. The percentage inhibition of AChE activity was significant for SPL and SPR at 750 and 1000 µg/ml.The leaves and root of Strophanthus preusii proved to be potent natural antioxidants and could justify their traditional use in the management of stress-related diseases.
